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.
C4 I don't use this. C2 should change voltage when brake or clutch is pressed - should not matter how many switches are present before as they are in series.
IIRC we pretty much determined that is was a problem with the ECM (in the car the cruise was not working), as far as I know it was never swapped out to verify as the owner sometime needs a boot to do things.
If you are using the stock cruise system, C2 should not matter if you use Rockcrawls chip (he disables it in the code) - at worest case, just tie it to 12v.
anyways, here are my notes on what I use (highlighted) - everything else is removed unless the ECM cruise is going to be used (marked in pen).
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09:35 AM
sanderson Member
Posts: 2203 From: corpus christi, texas, usa Registered: Sep 2001
Originally posted by Mickey_Moose: C4 I don't use this.
Without power to C4 my theory is that the scan tool will always display a brake depressed message. But it sounds like that may not be a big deal if everything else is healthy
quote
Originally posted by Mickey_Moose: C2 should change voltage when brake or clutch is pressed - should not matter how many switches are present before as they are in series.
C2 can only change voltage if cruise control switch is in the on position. If cruise control switch is in off position it kills the power to this circuit so it doesn't matter if brake is depressed or not
On my project I started with a non cruise Fiero. I added two Fiero brake switches. One for the C2 circuit and a second for a vacuum release solenoid (salvaged from a Fiero). I retained the Caddy servo and wiring to/from the PCM. I'm not using the Fiero cruise control stalk. I added an on/off switch, a set/coast button and a resume/accel button all mounted in the console. Then ran a bunch of new wires to hook this all up. As soon as I get my PCM problems behind me we'll see if this hybrid system is going to work.
I'm interested in how you tubed yours up. My thinking is that I need to come from the vacuum source through the canister to the small connection on the servo. The big connection on the servo goes to the vacuum release solenoid. The system is confusing in the Caddy. Both the big and small lines disappear through the firewall. It almost looks like they use a mechanical valve for vacuum release instead of a solenoid
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02:38 PM
Jan 8th, 2009
Mickey_Moose Member
Posts: 7582 From: Edmonton, AB, Canada Registered: May 2001
Originally posted by sanderson: C2 can only change voltage if cruise control switch is in the on position. If cruise control switch is in off position it kills the power to this circuit so it doesn't matter if brake is depressed or not
On my project I started with a non cruise Fiero. I added two Fiero brake switches. One for the C2 circuit and a second for a vacuum release solenoid (salvaged from a Fiero). I retained the Caddy servo and wiring to/from the PCM. I'm not using the Fiero cruise control stalk. I added an on/off switch, a set/coast button and a resume/accel button all mounted in the console. Then ran a bunch of new wires to hook this all up. As soon as I get my PCM problems behind me we'll see if this hybrid system is going to work.
I'm interested in how you tubed yours up. My thinking is that I need to come from the vacuum source through the canister to the small connection on the servo. The big connection on the servo goes to the vacuum release solenoid. The system is confusing in the Caddy. Both the big and small lines disappear through the firewall. It almost looks like they use a mechanical valve for vacuum release instead of a solenoid
C4 - as I said, I am not using C4 on my personal car and I do not get the 'brake pressed' message unless my cruise is on and the brake (or clutch) is pressed.
I am using the Fiero system and as such is wired as shown in the FSM - it uses 2 switches, one on the clutch and one on the brake. These are in series with the on/off stalk switch and feeds C2. The coast/resume/set switches are all wired to the ECM's pins labeled as such. The ECM ouput's are then run to the 'servo' as labelled. The vacuum release solenoid is controlled via the ECM via F2 and not through any brake switch - the brake switch should only feed C2.
Vacuum lines:
Looking down on the throttle body PCV side: port closest to the IAC motor is for the EGR, then the large one feeds the PCV valve. The one below it feeds the charcoal canister feeds on the larger port, the left one feeds the canister marked vac control. This line is T'ed off and feeds the 'coffee can' on the cruise, the coffee can then feeds into the cruise vacuum valve (the part that holds the cable) and the output port of this feeds the vent valve.
hopes that makes some sense...
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09:04 AM
sanderson Member
Posts: 2203 From: corpus christi, texas, usa Registered: Sep 2001
C4 - as I said, I am not using C4 on my personal car and I do not get the 'brake pressed' message unless my cruise is on and the brake (or clutch) is pressed.
I am using the Fiero system and as such is wired as shown in the FSM - it uses 2 switches, one on the clutch and one on the brake. These are in series with the on/off stalk switch and feeds C2. The coast/resume/set switches are all wired to the ECM's pins labeled as such. The ECM ouput's are then run to the 'servo' as labelled. The vacuum release solenoid is controlled via the ECM via F2 and not through any brake switch - the brake switch should only feed C2.
Vacuum lines:
Looking down on the throttle body PCV side: port closest to the IAC motor is for the EGR, then the large one feeds the PCV valve. The one below it feeds the charcoal canister feeds on the larger port, the left one feeds the canister marked vac control. This line is T'ed off and feeds the 'coffee can' on the cruise, the coffee can then feeds into the cruise vacuum valve (the part that holds the cable) and the output port of this feeds the vent valve.
hopes that makes some sense...
Thanks. I've got the vacuum tubing right. I wired up the vacuum release solenoid as in a Fiero operated by a brake switch. Looks like I missed the F2 contact on the Caddy PCM. For some strange reason the Caddy FSM does not show any wires going to the vacuum realease valve on the cruise control wiring diagram
Edit and update - Yes I have F2 wired to control vacuum vent that is internal to the servo. It's the external vacuum release valve (I'm using a Fiero valve) that's the mystery. As I said I have it wired through a brake switch as in the Fiero. Pretty sure this should work
[This message has been edited by sanderson (edited 01-08-2009).]
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09:29 AM
Fieroseverywhere Member
Posts: 4242 From: Gresham, Oregon USA Registered: Mar 2006
Oh good. I'm glad you guys were able to continue the research. I was pulled away and haven't had the chance to get back to it.
So since I am not using the cruise I probably don't need to worry about the brake depressed on the scanner. Are we sure it does not cause any other issues? I haven't found any but seat time in my car has been very limited so far. I'd still like to eliminate it if possible.
EDIT: Wait a second. In my 92-93 deville only FSM I'm seeing..
B3 - c/c position high B4 - c/c position low C2 - c/c enable C3 - c/c resume D2 - c/c on/off D3 - c/c set/coast F2 - c/c vent F3 - c/c source The c/c brk sw has two wires. Brn wire goes to C2, gra wire goes to D2 with a wire from the cruise stalk. So putting +12v to C2 should get rid of the brake depressed message for me. A better way would be to run a wire from the fiero brake switch. I, apparently, don't have a fiero FSM so I'm not sure where to get this wire other then the switch itself.
[This message has been edited by Fieroseverywhere (edited 01-08-2009).]
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07:22 PM
Fieroseverywhere Member
Posts: 4242 From: Gresham, Oregon USA Registered: Mar 2006
I am using the Fiero system and as such is wired as shown in the FSM - it uses 2 switches, one on the clutch and one on the brake. These are in series with the on/off stalk switch and feeds C2.
This is what I need. Where does the brake wire come from? Does it have a pin in the C500 or do I have to go under the dash to tap into it? My fiero never had cruise from the factory which is why I haven't bothered to add it.
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08:13 PM
Jan 16th, 2009
sanderson Member
Posts: 2203 From: corpus christi, texas, usa Registered: Sep 2001
This is what I need. Where does the brake wire come from? Does it have a pin in the C500 or do I have to go under the dash to tap into it? My fiero never had cruise from the factory which is why I haven't bothered to add it.
On Fiero power goes through the "on" switch on cruise control stalk and then splits. One split goes directly to the ECM (late 4 cyl) or cruise control module (V-6). The other split goes to a brake/clutch switch(es) and then to the ECM (late 4 cyl) or the cruise control module (V-6). When wiring up a Caddy the direct wire goes to D2 and the switched wire goes to C2. If your Fiero did not have cruise the brake switch is not there and IIRC neither are the wires.
On auto Fieros there is another brake switch. Power goes through it and then to torque converter clutch. This goes through C203-P and into the engine harness to the transaxle. I'm not sure if this switch and wiring is there on a manual Fiero. When wiring up a Caddy the C203-P wire goes to the TCC but is also splits and goes to C4 on the PCM.
With a fresh PCM in my car the "brake depressed" message on the scan tool is working. I can turn it on or off by depressing the brake pedal. I do not have the cruise switched on so I have NO POWER to D2 or C2. The brake depressed message is not on normally. I can turn it on by depressing the brake pedal but it has to be the second brake switch wired to C4 that it causing this to happen.
Mickey Moose said he has no power to C4 and does not normally have the the brake depressed message. If he's running a non stock chip maybe this was programmed out. He does get it the brake depressed message if the cruise control is ON and he steps on the brake pedal.
It appears that either brake switch can activate the brake depressed message. But the PCM only looks at C2 if it sees power on D2.
If the brake depressed message is normally on, I still think power has to be supplied to C4 to turn it off.
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07:36 PM
josef644 Member
Posts: 6939 From: Dickinson, Texas USA Registered: Nov 2006
Success - swapped in a new junkyard PCM with a VATS bypass module and I've got full power and all the gears.
One bit of strangeness left. I've got a code 52 memory reset error and it lights the SES light. I can clear it with the scan tool but it comes back after about 10 seconds. I swapped in another PCM and it does the same thing. I checked for unswitched power on C16 and B1 and it's there. Also checked the grounds for resistance and they're fine.
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10:01 AM
Mickey_Moose Member
Posts: 7582 From: Edmonton, AB, Canada Registered: May 2001
On Fiero power goes through the "on" switch on cruise control stalk and then splits. One split goes directly to the ECM (late 4 cyl) or cruise control module (V-6). The other split goes to a brake/clutch switch(es) and then to the ECM (late 4 cyl) or the cruise control module (V-6). When wiring up a Caddy the direct wire goes to D2 and the switched wire goes to C2. If your Fiero did not have cruise the brake switch is not there and IIRC neither are the wires.
On auto Fieros there is another brake switch. Power goes through it and then to torque converter clutch. This goes through C203-P and into the engine harness to the transaxle. I'm not sure if this switch and wiring is there on a manual Fiero. When wiring up a Caddy the C203-P wire goes to the TCC but is also splits and goes to C4 on the PCM.
With a fresh PCM in my car the "brake depressed" message on the scan tool is working. I can turn it on or off by depressing the brake pedal. I do not have the cruise switched on so I have NO POWER to D2 or C2. The brake depressed message is not on normally. I can turn it on by depressing the brake pedal but it has to be the second brake switch wired to C4 that it causing this to happen.
Mickey Moose said he has no power to C4 and does not normally have the the brake depressed message. If he's running a non stock chip maybe this was programmed out. He does get it the brake depressed message if the cruise control is ON and he steps on the brake pedal.
It appears that either brake switch can activate the brake depressed message. But the PCM only looks at C2 if it sees power on D2.
If the brake depressed message is normally on, I still think power has to be supplied to C4 to turn it off.
Good to hear you got it figured out.
Yes, could be as you say with my car, Rockcrawl did the programming - I did specify that I was using a manual car and was going to use the ECM's cruise ouptuts to drive the cruise, so he may have disabled the VCC brake in the programming (I have no real ideal what he did). My car is also originally a standard car with factory cruise, I just remove the Fiero's cruise module and ran the wiring straight to the ECM.
Anyways, good on you for figuring it out. I would have to look more into the code 52 problem.
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11:27 AM
PFF
System Bot
Feb 2nd, 2009
sanderson Member
Posts: 2203 From: corpus christi, texas, usa Registered: Sep 2001
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
The speedometer problem turned out to be a blown radio fuse provides power the Fiero speedometer. The speedometer works fine after finding that
