After 2+ years of messing with this 4.9 swap, I'm finally getting it on the road. The engine has 30,000 miles on it and came out of a '92 Deville. I used the Deville as a daily driver before pulling the engine and it was a strong runner.

Now that the engine is in the Fiero it is a shadow of its former self. It idles smoothly but at WOT it's got nothing. It doesn't miss while trying to accelerate - it just does not pull.

I knew about the power steering pump wiring when I built the harness and I'm pretty sure I've got 12V hooked to the PS input on the PCM. This is on my list of things to verify when I get back to working on the car on 1/1/09. I don't think that this is the problem because the scan tool says the PCM is going into "learn enable"

The scan tool also says the PCM is going into closed loop. With the engine idling the O2 sensor is moving around, the integrater is staying about 128 and I'm seeing O2 cross counts. All this seems real normal.

I've checked the timing and it is normal

I've checked the fuel pressure and I have 42 psig at the rail

One thing that does seem a bit strange is that the manifold air temperature is running very hot. It gets as high as 200 'F while idling. The duty cycle on the EGR is at 99%. Does the EGR heat up the intake air this much?

Also I have a code 52 memory reset error and code 24 VSS sensor error that the scan tool will not clear. The SES light is not on. I have checked and I have unswitched power to the correct two terminals on the PCM so I'm mystified why the scan tool is showing the code 52. The scan tool is also able to read the vehicle speed going down the road so it's also strange that I have the code 24. The scan tool is an AutoXray 6000.

I need to educate myself some more on my scan tool but intend to try a data capture of a WOT run and see the pulse width on the injectors

Anybody else got some ideas?

First off, congrats on getting it running. Once it's running right, you will have a perpetual grin on your face every time you drive it.

The 4.9 should pin you in your seat from a dead stop. At least mine does.

OK your fuel pressure is good at idle. Is it holding at 42 psi at WOT? You may have to tape the guage up and use your mirror to verify, or have a passenger peek over his shoulder...one of those odd Fiero things. And I have seen pumps that provide sufficient flow at idle to produce 45 psi....and then fall on their faces at WOT. Have you checked all injectors with a noid light to verify that they are firing?

Next, you say normal....what is your base timing set at, and are you seeing an advance as you open the throttle? I'm wondering if the PCM is advancing timing at WOT. The 12V to the PS cavity on the PCM would cause a rich mixture, but I doubt it would result in your symptoms.

How many inches of vacuum at idle?

What kind of exhaust setup do you have, and have you checked for any obstructions ....ie...blown out cat, muffler, etc? Remember, it's gotta be able to exhale as well as inhale. A comparison between a static and running compression test will help point you in that direction. If compression is high with all plugs removed, and low in all cylinders with it running, there is a blockage downstream.

Are you 100% positive that the butterflies are opening completely when you mash the throttle...no misadjusted or binding cable? I had a high idle on my 4.9 I couldn't pin down...turned out I had bent the throttle cable bracket leaning on it and it wasn't letting the butterflies close...sometimes it's the silliest stuff.

What's confounding me is that you have no miss or other symptoms beyond no power. That in and of itself is a symptom. You mentioned the EGR duty cycle at 99%....this is where I would start looking.

Engine swaps are a little tougher to diagnose than factory stuff, but it all still runs on the same principles. Tell me your fuel pressure at WOT, your base timing setting, your vacuum readings, check for exhaust obstructions, test your EGR valve, and tell me what you have.

I know Brocephus is waiting for this....so here it is. They need 3 things to run correctly;

1. Suitable compression
2. A suitably strong spark delivered at the correct time.
3. The correct mixture of fuel and air for a given speed and load.

If those 3 conditions are met, they run. Our job now is to determine which of the three conditions above is deficient, and address the deficiency.

I don't have the listing of DTC's for the 4.9 sitting in front of me, so someone else will have to chime in with analyzing your data log.

I love a good challenge....maybe I can learn a thing or two that might prove useful on my swap later as well. Good luck and happy wrenching.

quote Originally posted by Frizlefrak: OK your fuel pressure is good at idle. Is it holding at 42 psi at WOT? You may have to tape the guage up and use your mirror to verify, or have a passenger peek over his shoulder...one of those odd Fiero things. And I have seen pumps that provide sufficient flow at idle to produce 45 psi....and then fall on their faces at WOT. Have you checked all injectors with a noid light to verify that they are firing?

Good thoughts I'll check these out next weekend.

quote Originally posted by Frizlefrak: Next, you say normal....what is your base timing set at, and are you seeing an advance as you open the throttle? I'm wondering if the PCM is advancing timing at WOT. The 12V to the PS cavity on the PCM would cause a rich mixture, but I doubt it would result in your symptoms.

I probably over stated my confidence in the base timimg. Its at about the second point location on the indicator. I couldn't read the numbers to get the exact reading. This was with A-B shorted on the ALDL and the timing light on what I remembered as the #1 cylinder (front/passenger side). Months ago when I first set it I knew the exact value and had figured how many degrees there were per point on the indicator. The most recent timing exercise got cut short when the serpentine belt ate the clamp on the timing light. More work to do on this next weekend.

The PCM is advancing the timing. I know I saw a number as high as 49 degrees while drving the car to safety inspection today.

quote Originally posted by Frizlefrak: How many inches of vacuum at idle?

not sure how many inches but read about 1 volt on the MAP at idle. I'll put a gauge on it next weekend

quote Originally posted by Frizlefrak: What kind of exhaust setup do you have, and have you checked for any obstructions ....ie...blown out cat, muffler, etc? Remember, it's gotta be able to exhale as well as inhale. A comparison between a static and running compression test will help point you in that direction. If compression is high with all plugs removed, and low in all cylinders with it running, there is a blockage downstream.

It a Deville set-up with the crossover pipe. Exhaust is a vertical cat to a tee and then to a glasspack on each side. All new stuff. Hard to imagine it could be plugged. I plan on checking the compression in at least the back cylinders next weekend. How do you do a running compression test?

quote Originally posted by Frizlefrak: Are you 100% positive that the butterflies are opening completely when you mash the throttle...no misadjusted or binding cable? I had a high idle on my 4.9 I couldn't pin down...turned out I had bent the throttle cable bracket leaning on it and it wasn't letting the butterflies close...sometimes it's the silliest stuff.

Another thing to check. Pedal seems to go all the way down so I don't think this is the problem.

quote Originally posted by Frizlefrak: What's confounding me is that you have no miss or other symptoms beyond no power. That in and of itself is a symptom. You mentioned the EGR duty cycle at 99%....this is where I would start looking.

Is it normal for the PCM to command 99% duty cycle on the EGR at idle?

One other thing I just remembered is that it does tend to bog before revving up if you blip the throttle fast from idle.

Is it a timing chain or belt? One or two teeth retared will have a good idle and take off but no High end.

quote Originally posted by sanderson: I was missing the ground wire for the neutral safety switch. It shifts through the first three gear for sure now. Don't think I'm getting fourth gear. At least that's what the scan tool says and it doesn't feel like it either.

OK....we're getting somewhere. First, running vs static compression test

http://www.misterfixit.com/dyncompr.htm

But in your case, if all exhaust components are relatively new, they probably aren't suspect. And given that you're using a known good low mileage engine, I don't believe you have a compression issue. But I wanna know what's going on with your transmission before we go any further. You should have around 1900 rpm @ 70 mph or thereabouts with the 4T60E. If the tach is reading in the high 2000 range, it's still in 3rd gear. In the case of our drivetrains, the PCM controls....well....the powertrain. And they are symbiotic, if you will. If one coughs, the other can catch cold. This is going to have to be fixed eventually....now is a great time. And you might just kill both birds with one stone.

Reading back, you built your own harness. And your engine runs, so you obviously did at least most of it right. But if you had all 4 gears when it was in the DeVille and now you don't, something is amiss. If it's any consolation, both of the harnesses we used from Injection Technology had issues we had to correct on the swaps, so you are doing as good as the pros. And in both cases, it was a week to find the problem and 5 minutes to rectify it.

I'd also like a little info on how you got the Caddy PCM to play nice with the Fiero speedometer. I bought the premade harness, and it comes with the module to make the Caddy PCM and the Fiero speedo simpatico. This is all a little out of my area of expertise, so I will defer to the experts, but that code 24 you're getting is setting off sirens in my head. And it could be why your car won't shift into overdrive....the PCM is seeing a loss of signal from the VSS and doesn't think the car is moving.

https://www.fiero.nl/forum/Forum2/HTML/091019.html

https://www.fiero.nl/forum/Forum2/HTML/079902.html

Soo...looks like I got long winded again Run the tests outlined before, and then I would advise nailing the trans issue first. I really feel like something is wired wrong and is causing this problem. But, it's late, I've had the flu for 5 days now, and my head is a little foggy from the meds. If you don't have them, I have the wiring diagrams for a 1992 from the Helms manual buried in my swap file, or someone will probably post them first. I would check wire by wire and ensure that everything is going to the right place.

quote Originally posted by Frizlefrak: I'd also like a little info on how you got the Caddy PCM to play nice with the Fiero speedometer. I bought the premade harness, and it comes with the module to make the Caddy PCM and the Fiero speedo simpatico. This is all a little out of my area of expertise, so I will defer to the experts, but that code 24 you're getting is setting off sirens in my head. And it could be why your car won't shift into overdrive....the PCM is seeing a loss of signal from the VSS and doesn't think the car is moving.

I installed the Rockcrawl clamp circuit but speedmoter is not working - another thing to check next weekend. So theoretically I could have a VSS problem. What is strange is that the scan tool is displaying vehicle speed which I would have thought indicates that the VSS circuit is working and PCM is seeing vehicle speed. Code 24 is set if the PCM doesn't detect vehicle speed but the car is in gear at over 1400 rpm.

P.S. I have a '92 Deville factory service manual and '88 Fiero factory service manual so I'm in pretty good shape on wiring diagrams

On mine, a ground was missing to the idle air control valve. It apparently went through the original harness towards the firewall and I deleted it. The IAC would hunt and act very goofy. I added a ground right to the valve connector and it cleared right up. Ran fine, but no power and would really bog when you gave it throttle.

quote Originally posted by jfoster142: On mine, a ground was missing to the idle air control valve. It apparently went through the original harness towards the firewall and I deleted it. The IAC would hunt and act very goofy. I added a ground right to the valve connector and it cleared right up. Ran fine, but no power and would really bog when you gave it throttle.

Good tip. I see the ground on the wiring diagrams but I'm drawing a blank on whether I picked it up or not

quote Originally posted by sanderson: P.S. I have a '92 Deville factory service manual and '88 Fiero factory service manual so I'm in pretty good shape on wiring diagrams

OK good, same manual I have. I'm wondering if something is missing in the wiring that is limiting injector flow at WOT. I'm still baffled at how it has no power, but runs smoothly and doesn't miss....and is going into closed loop. The only explanation is that fuel flow into the cylinders is being limited by something.....something that is misleading the computer into thinking a certain condition exists when it doesn't. I'd be interested to see the pulse width on the injectors...any luck with the scan tool?

quote Originally posted by Frizlefrak: I'd be interested to see the pulse width on the injectors...any luck with the scan tool?

My hobby shop is at our weekend property 190 miles away. I won't get back to work on it until New Year's Day. But then I'll have three days to try to get to the bottom of this mystery. I like you think it is something simple in the wiring - days to find and minutes to fix. Could be the throttle position switch that JFoster mentioned.

auto or manual??

Chip reprogrammed??

Sounds like the car is in limp mode, which basically means you probably missed something in the wiring. I don't see a point in wasting time trying to figure out injector pulse width, etc - the ECM in not seeing something and put itself into limp mode. This is something you really can't find with a scanner.

Code 52 is normal when the ECM has been disconnected from power for a long time. Code 24, I am not sure if this will cause limp mode - try resetting the ecm (disconnect battery for 10 - 20 minutes - should clear any codes). SES light should come on with the code 24 - may want to check that wiring (A10) - also check that the bulb is good.

If using a manual transaxle: you MUST have F7 and C10 going to ground - ALSO, your chip needs to be reprogrammed. The 4.9 ECM is looking for a 26000 ppm signal from the VSS, if you are only feeding it 4000 ppm (stock Fiero) - then that may be a problem.

C9 to +12v power steering input (but you know that already).

Check all your ground and power connections to the ECM.

Mickey.,..he's using the 4T60E, and doesn't have 4th gear for some reason. I can't help but think this is related to the performance issue. Something is miswired.

[This message has been edited by Frizlefrak (edited 12-29-2008).]

quote Originally posted by Mickey_Moose: Sounds like the car is in limp mode, which basically means you probably missed something in the wiring. I don't see a point in wasting time trying to figure out injector pulse width, etc - the ECM in not seeing something and put itself into limp mode. This is something you really can't find with a scanner.

Maybe - my impression from other posts is that limp mode only gives second gear. Since finding missing ground on neutral/safety switch I now have first three gears. Plus would the PCM go into closed loop and learn enable in limp home mode? Maybe someone else here can confirm what limp home mode consists of.

quote Originally posted by Mickey_Moose: Code 52 is normal when the ECM has been disconnected from power for a long time. Code 24, I am not sure if this will cause limp mode - try resetting the ecm (disconnect battery for 10 - 20 minutes - should clear any codes). SES light should come on with the code 24 - may want to check that wiring (A10) - also check that the bulb is good.

I realize that code 52 is set whenever the battery is disconnected. The struggle I'm having is why the scan tool won't clear it once the car is powered up

When I first found code 24 the SES light was on and I found the VSS unplugged. Plugged in VSS, cleared codes with the scan tool and SES light went out . Later I went and checked for codes again even though SES light was not on. Found code 24 and code 52. Neither would clear. Do need to make sure SES bulb didn't burn out half way through this process.

quote Originally posted by Mickey_Moose: Check all your ground and power connections to the ECM.

I'm going to go through all the pins on the PCM connectors and make sure that they are going to the right place

P.S. chip was reprogrammed by Cooter here on Pennocks to remove VATS, remove speed limiter and lower set point for fan on. No other changes.

[This message has been edited by sanderson (edited 12-29-2008).]

Double check the wiring to the EGR silonoid. I had an issue with mine that I had missed the wire on the firewall side. This silonoid not working properly did not set a SES light but really hurt the power at anything above idle. It still idled perfectly. Limp mode is slightly different but similar. Deffinately worth looking into.

EDIT: Adding more info. 99% EGR is normal at idle. At least on mine it stays open til higher RPM's.
Your VSS is getting the signal to PCM if you have a speed reading on scanner. Doesn't matter if the speedo is working or not. Will not effect the engine as long as the signal is getting to the PCM. I have had a couple codes that did not clear immediately. Probably what is going on here.
On scanner, 4th digit "B", 8th "D". I have an auto-x-ray 3000. Same as yours but not OBD2.

[This message has been edited by Fieroseverywhere (edited 12-29-2008).]

IIRC some other changes are needed in the eprom to prevent issues - you will need to talk with Rockcrawl about this (or maybe you can try PBJ).

As far as I know, you can't clear codes with a scanner on OBD1 systems, they reset themselves once the problem is resolved - but hey I could be wrong.

TPS has a dead spot at WOT?? Do you have access to another chip that you can toss in there to try? Does the IAC motor move in and out as soon as you turn the key off after driving the car?

If the setup was working before (in original car), the only thing that has changed is the wiring. It can be a real pain to start going through it, but that is where I would start. This is easier with a helper, one sits in the car and puts the meter lead on each pin, the other connects to the pin on the other end of the harness in the engine bay.

quote Originally posted by Fieroseverywhere: EDIT: I had a PROM error for the longest time on mine (chip not programmed right). This caused "limp mode" even though nothing was wrong. I believe the car would still go into closed loop but can't remember for sure.

Interesting. Do you recall if the transmission shifted? I am bothered by the fact that I'm seeing code 52 and code 24 when I shouldn't have them. Also why no fourth gear. So maybe the chip did get corrupted in the reprogramming process.

At any rate I am going to:

1) Go through the wiring harmess with a fine tooth comb

2) Check the fuel pressure at WOT

3) Capture a snap shot of data with scan tool at WOT

4) Check compression

5) Check all injectors with noid light

If all that fails, I'm going to junk yard for a new PCM and I'll install that with a VATS bypass module and see what happens There were several '91 Devilles and one '92 at the junk yard last time I was there. Anybody know if the the '91 is wired the same as '92? Do I need 30 Hz or 50 Hz signal with these PCM's

4.9L engines should have the firing order and cylinder designation cast into the intake manifold...

Check fuel pressure during your problem spots.

quote Originally posted by sanderson: Interesting. Do you recall if the transmission shifted? I am bothered by the fact that I'm seeing code 52 and code 24 when I shouldn't have them. Also why no fourth gear. So maybe the chip did get corrupted in the reprogramming process. At any rate I am going to: 1) Go through the wiring harmess with a fine tooth comb 2) Check the fuel pressure at WOT 3) Capture a snap shot of data with scan tool at WOT 4) Check compression 5) Check all injectors with noid light If all that fails, I'm going to junk yard for a new PCM and I'll install that with a VATS bypass module and see what happens There were several '91 Devilles and one '92 at the junk yard last time I was there. Anybody know if the the '91 is wired the same as '92? Do I need 30 Hz or 50 Hz signal with these PCM's

Mine is a manual so I have no idea on the shifting. Sorry.

I would head for the EGR silonoid wiring first. Because with this engine the EGR is electrically controlled by the PCM I think this is what is giving you the issue. I can cause the high intake temps and loss of power above idle. I missed the power wire on mine and it gave me problems just like this.

It you go for a new PCM get one from a 92-93 (deville, fleetwood, 60 special). These are the only ones (EPROM) that work and can be reprogrammed. The 91's are not eraceable (PROM). 91's will work if you plan keeping stock programming but you may want to change that later. You don't even want to know how I found this out... Also get the VATS from the same car you get the PCM from.

You will probably want to check out the VSS circuit also. That is probably why you still get the SES light for that one. Last night I had a thought that maybe whoever did the VSS programming in the chip changed it when they shouldn't have. Your using the stock caddy trans and VSS sender so your chip shouldn't need changed for that. Just add signal clamp for fiero speedo.

EDIT: The memcal you want has a black base to it. The non eraceable one has a brown base. Get the right one if you want the programming to be saved. FYI

[This message has been edited by Fieroseverywhere (edited 12-30-2008).]

quote Originally posted by sanderson: Do I need 30 Hz or 50 Hz signal with these PCM's

You need the 30 Hz. It was used from 1991-1993. The 50 Hz was used on the 94.

Got back to this project again today.

Checked for power to the EG R valve

Checked the ground on the throttle position switch and that was good also

SES bulb tests okay

Throttle plates open all the way

Started checking the rest of the harness and found insulation cracked off both wires near No 1 injector with possibility that they were shorting. Fixed this up with electrical tape and decided to take the car for a drive.

Took off and found it was stuck in second gear and no power. Ran the scan tool. Had the code 52 error but this time no code 24. SES light was not on. Ran through all the data and noticed that scan tool was seeing a "brake depressed" signal. Took the car home. Pulled the plugs on the PCM and checked for voltage on the PCM C1-C4 pin. It was seeing voltage so the "brake depressed" message should not have been there. Plugged the the PCM connectors back in and rescanned. This time no 'brake depressed" signal. Took the car for a short drive and finally it shifted and ran with expected power. Went out to dinner to celibrate. When I came back decided to take the car out and see if fourth gear worked. Started it back up and ran scan tool and "brake depressed" signal was back. Took it down the road and its back stuck in second gear with no power.

When I first started running the scan tool, I initially had the "brake depressed" message. It went away on it's own while i was tracking down the missing ground on the neutral safety switch and I sort of forgot about it.

So I'm back looking at the brake switch circuit.

But my suspicions on the PCM have been raised more.

[This message has been edited by sanderson (edited 01-01-2009).]

Well, first off, congrats on at least isolating the problem. Now on to fixing it. I think something went wrong with the burn on your chip. I had the same issue....had a chip burned by someone here on the forum. Worked fine first time I drove it, but when I shut the car off, the transmission was stuck in 3rd and I had to hold the accelerator pedal to the floor to start it. I could remove power to the PCM...thus "rebooting" it, and it would run fine....once. Then it would have to be rebooted again or no gears.

I went back to using a stock PCM and memcal and no problems since. You might try picking up a spare memcal and have Cooter burn another chip and see if it works better, or grab a factory PCM from the junkyard and just use a VATS module.

If you can refresh my memory on what was needed to be done on the chip, I'll see if I have an extra memcal and will program it and send it out. It would be good if you had the broadcast code for your engine/tranny. I misplace stuff from time to time and may have to do some searching to find the right base program. I've had memcals that took the program fine, but would go goofy when used. No real reason for it that I could find, but it happens. I did not know that the brown memcals would not work- I've got a stack of them too Live and learn.

quote Originally posted by sanderson: Took the car for a short drive and finally it shifted and ran with expected power. Went out to dinner to celibrate. When I came back decided to take the car out and see if fourth gear worked. Started it back up and ran scan tool and "brake depressed" signal was back. Took it down the road and its back stuck in second gear with no power.

I had a similar problem with a couple of chips that someone had burned for me.
(The first drive was fine. Subsequent drives started out in second gear, engine idled at ~ 1400, Seemed to be running in "limp home" mode. A "reboot" fixed it until the next drive.) This was before I had my scan tool, so I don't know what it was seeing.

I'm thinking they were probably the wrong broadcast code, since the same tune ran fine in other peoples' cars.
Since all the engines and PCMs are the same, it really baffles me why they are not interchangeable. Perhaps it has to do with the FDR in the tranny. That's one major difference I can think of between the 4.9s.

There are at least four different "families" of 4.9 broadcast codes.

[This message has been edited by Raydar (edited 01-02-2009).]

quote Originally posted by Raydar: Since all the engines and PCMs are the same, it really baffles me why they are not interchangeable.

There were two different PCM's used for the 4.9. The 1991-1993 used and the 2240 PCM and the 1994 used the 6347 PCM. I don't know what, if any, difference there is between the two.

Interesting that you had the same "no shift until reboot" issue I had.

quote Originally posted by Frizlefrak: There were two different PCM's used for the 4.9. The 1991-1993 used and the 2240 PCM and the 1994 used the 6347 PCM. I don't know what, if any, difference there is between the two. Interesting that you had the same "no shift until reboot" issue I had.

1995 also used the 6347 PCM.

There are also some minor wiring diferences between the DeVille, SeVille and Fleetwoods which would account for different programming - which seems odd since the ECM's between the same years are the same. IIRC the differences are with the O2 sensor and a couple of the transmission wires (I think there was something else).

But I do know that you have to burn your chip to match the model that you wired it up as or errors do show up.

quote Originally posted by Cooter: If you can refresh my memory on what was needed to be done on the chip, I'll see if I have an extra memcal and will program it and send it out. It would be good if you had the broadcast code for your engine/tranny. I misplace stuff from time to time and may have to do some searching to find the right base program. I've had memcals that took the program fine, but would go goofy when used. No real reason for it that I could find, but it happens. I did not know that the brown memcals would not work- I've got a stack of them too Live and learn.

All we did is remove the VATS, remove the speed limiter, and lower fan on set point. Let me get a fresh ECM (they're cheap at Pick-n-Pull) and see if I can run with a VATS bypass module. If that works then I'll get back with you to remove the speed limiter and lower the fan on set point. I handled the chip without a ground strap on so maybe it got a shot of static. Like you say things happen.

[This message has been edited by sanderson (edited 01-03-2009).]

quote Originally posted by sanderson: I rechecked the C1-C4 "brake depressed" wire to the PCM for voltage and had 12 volts. Even checked it with a test light to make sure it wasn't a flaky connnection and it lit the light. Still have the "brake depressed" message on the scan tool. Next checked all the ground wires on the PCM plugs for resistance and found 0 ohms on all them. I'm headed off tomorrow morning for a new PCM

My scanner has always showed this also. It doesn't seem to make a difference with the manual trans. Keep us posted on your solution. Now you have me thinking about it again.

quote Originally posted by Fieroseverywhere: My scanner has always showed this also. It doesn't seem to make a difference with the manual trans. Keep us posted on your solution. Now you have me thinking about it again.

It's funny, this does not happen on my car, yet on another car it does (same scanner). We were trying to figure out why the cruise (we are using the ECM to control the cruise, not the stock Fiero one) was not working on the car that showning brake depressed. Is not the chip, because I put his chip into mine and it work fine (I can not put my chip into his due to the passkey is active on my car and is hardwired into the security system) - yet the wiring seems correct. The only real differences between the cars is one is a 5 speed and the other is a 4 speed. Haven't spent too much time on it to find a solution - maybe in the summer. However, this car shows no other problems.

I picked up two PCM's yesterday; a '92 Deville with a BWYH chip and a '92 Fleetwood with a BWYM chip. Need to order a VATS bypass module so it will be a couple of weeks before I get back to it

quote Originally posted by Mickey_Moose: It's funny, this does not happen on my car, yet on another car it does (same scanner). We were trying to figure out why the cruise (we are using the ECM to control the cruise, not the stock Fiero one) was not working on the car that showning brake depressed. Is not the chip, because I put his chip into mine and it work fine (I can not put my chip into his due to the passkey is active on my car and is hardwired into the security system) - yet the wiring seems correct. The only real differences between the cars is one is a 5 speed and the other is a 4 speed. Haven't spent too much time on it to find a solution - maybe in the summer. However, this car shows no other problems.

Mine is a 5 speed now but being converted to a 4 speed. I don't think it will make a difference but I will keep an eye out during the conversion. The only difference in wiring is the reverse light switch. I believe all 85-88 are wired for both switches. I know my car is. I figure it must be a wiring issue since I have 2 proms from different people and they both do it.

I was wondering if the fiero brake switch is wired differently then the caddy one. Maybe they changed it at some point and the different years are the issue? Whats really odd is pressing the brake does nothing. I don't have a clue but since it doesn't seem to matter in my swap I'm not trying that hard to fix it.

Well now you've done it! I'm pulling out the service manual again to check out the wiring...

I'm back in Corpus Christi and only have a '94 FSM to look at but what I see is:

D2 - cruise enable input
C2 - cruise brake switch input
C4 - TCC brake switch input

Neither D2 or C2 should have power if the cruise control switch is off. In my case I'm wired for cruise but it is off and the scan tool says it's off. Some of the time the scan tool says the brake pedal is depressed and sometime it doesn't. When I see it not depressed I have been able to change the state on the scan tool by depressing the brake. I think the C4 contact is what toggles the brake depressed message on the scan tool.