I recently bought a 3800SC car and it is throwing a few codes. The motor is from a 2004 Grand Prix GTP 4t-65eHD trans pcm programed by fieroflyer.
P0135 Powertrain O2 Sensor heater circuit (bank 1 sensor 1)
P0300 Powertrain Random/Multiple Cylinder Misfire Detected
P0134 Powertrain O2 Sensor Circuit No Activity Detected (bank 1 sensor 1)
P0480 Powertrain Cooling Fan 1 Control Circuit (I think that was just a fluke or old code, because I let it run long enough for the fan to kick on, and everything works with no codes now)

I am assuming that the 2 O2 sensor codes are related, what should I check? I looked at all the wiring around there, everything looks connected and nothing looks melted or anything.
It seems to hunt around for idle when you start it cold and will rev up to like 2,500 and fluctuate a lot, if you feather the gas and let it warm up a little it will settle down and idle real nice. Not sure if that would related at all.
As far as the misfire, I found a loose plug wire, cleared the code and started it back up. It runs 100% smoother and I can't hear any kind of misfire, but the code came back. Used the torque app and pulled up current misfires for each cylinder and it was not picking anything up, but I am real new to that app so I may be doing something wrong.

Any suggestions would be appreciated.

[This message has been edited by zmcdonal (edited 04-23-2015).]

Is the O2 heater circuit ran through the PCM like it was originally wired in 2005? Or is it just wired straight up? First unplug the PCM. Turn the key to on and let is sit for a few minutes. Does the O2 heater get warm? If so it is is not wired through the PCM but the PCM is still programmed for it to be wired through it.

P0134 abd P0135 could have been set by having the O2 sensor unplugged.

Assuming your PCM has the two 80 pin connectors - PCM unplugged - Key on - AC off. Using a paperclip on the BLUE connector - Does grounding pin 5 turn on the radiator fan? Does grounding oin 6?

quote Originally posted by phonedawgz: Is the O2 heater circuit ran through the PCM like it was originally wired in 2005? Or is it just wired straight up? First unplug the PCM. Turn the key to on and let is sit for a few minutes. Does the O2 heater get warm? If so it is is not wired through the PCM but the PCM is still programmed for it to be wired through it. P0134 abd P0135 could have been set by having the O2 sensor unplugged. Assuming your PCM has the two 80 pin connectors - PCM unplugged - Key on - AC off. Using a paperclip on the BLUE connector - Does grounding pin 5 turn on the radiator fan? Does grounding oin 6?

Well when I cleared the P0300 code to see if it would come back, it also cleared the P0134 and P0135, when I started it up again I think the only one that came back was P0300 but I didn't let it run very long because it's leaking coolant from one of the hoses, I think I need a new fitting on the rear fill reservoir. How long does the computer store codes? Because there was no battery in the car for a long time before I bought it.

When you say to unplug the PCM, I unplug both connectors from it? Just want to make sure. As far as the O2 heater, would I feel the sensor itself to see if it feels warm or where exactly is the heater?

Thanks for the help.

Some are stored forever, others are not

Both connectors

Yes with a cold engine just feel the outside of the O2 sensor to see if it is getting warm.

quote Originally posted by zmcdonal: Well when I cleared the P0300 code to see if it would come back, it also cleared the P0134 and P0135, when I started it up again I think the only one that came back was P0300 but I didn't let it run very long because it's leaking coolant from one of the hoses, I think I need a new fitting on the rear fill reservoir. How long does the computer store codes? Because there was no battery in the car for a long time before I bought it. When you say to unplug the PCM, I unplug both connectors from it? Just want to make sure. As far as the O2 heater, would I feel the sensor itself to see if it feels warm or where exactly is the heater? Thanks for the help.

[This message has been edited by phonedawgz (edited 06-15-2014).]

[URL=http://s100.photobucket.com/us er/zdmcdonal/media/Mobile%20Uploads/20140616_190811_zpsp41abraw.jpg.html][/URL]
So here is the back of my PCM, I didn't get a chance to disconnect it and see what was going on yet but looking at the back I don't see that any of the connectors are blue. Do I need to unbolt the plug retainer part to see that? Thought I would ask before I went poking around there.

[This message has been edited by zmcdonal (edited 06-16-2014).]

The pin shields inside the connector are blue or clear plastic. The PCM is marked, but the installed connectors cover up the letters.....

I didn't unplug the PCM, but turned the ignition to the on position and left it for a couple minutes then felt the O2, didn't feel warm at all. Is is possible that it is not running a heated O2 any more and that code never was programmed out?

I've got a new code showing up as well.
P0171 Powertrain System too Lean (Bank 1)

Which from what I have read sounds like it could be something as simple as a vacuum leak. My car is also running a different MAF sensor than the typical one used for a 3800 swap, so maybe that's what's causing it? What's the best way to check for vacuum leaks? I have looked at all of the rubber lines I could see, and did not find anything loose or in bad shape.

It is still throwing the P0300 for random multiple misfires, and when I scanned this is what it showed




So it appears that cylinder 5 is the biggest problem. I have removed the metal heat shield boot protectors on the wires as I have been told that they can cause misfires. Is it necessary to buy aftermarket boot protectors when running stock manifolds? Right now I am running it without any. The wires are new and all appear to be in good shape, no visible burns or cuts in them. I removed the coil for cylinder 2/5 and re installed it in case there was a possibility that it was not seated properly or something crazy.

Any suggestions as to what I should do next to diagnose the issues? Thanks.

[This message has been edited by zmcdonal (edited 08-15-2014).]

For P0134 and P0135

Is there a pin in 37 Clear? This is where the Heated O2 sensor heater should ground to. Normally that is a Black/White wire

What MAF are you running?

At idle what are you getting for MAF?

[This message has been edited by phonedawgz (edited 08-15-2014).]

quote Originally posted by phonedawgz: For P0134 and P0135 Is there a pin in 37 Clear? This is where the Heated O2 sensor heater should ground to. Normally that is a Black/White wire What MAF are you running? At idle what are you getting for MAF?

It seems to be picking up the O2 heater now, I unplugged the O2 sensor and plugged it back in. In the emissions readout screen on torque it recognizes the O2 heater now where it didn't before.

I think it might be an LS1/LQ4 MAF. I'm not entirely sure. I've just trying to match up pictures with what I have, and what I know has been done.

At idle the MAF (g/s) is 8.2

Here is a picture of how it's setup.





Earlier today I unplugged the MAF and started it up and it seemed to run MUCH smoother. The RPM's were a little higher at idle but when I was looking at the misfire count for each cylinder it was almost 0. I don't know if that's due to a higher RPM or not though.

[This message has been edited by zmcdonal (edited 08-15-2014).]

I'm running about 7.3 on my 98 3800 NA.

Did FieroFlyer program your PCM for your MAF? Different MAFs have different responses. If your PCM isn't programmed for your MAF you're going to have problems. It sounds like your MAF isn't programmed correctly for your MAF.

I have no idea if it's programed for that MAF. I bought the car this way, trying to figure it all out. Does it sound like that could be causing the misfire code and lean condition to you?

Could be - When you disconnect the MAF the PCM instead of using the data coming from the MAF uses pre-programmed assumptions of what the MAF would be reading. That should give you a reduction in performance. So it appears that either the data coming from the MAF is incorrect, or the way the PCM is translating the information is incorrect.

Perhaps a vacuum leak is making the actual air flow through the MAF be incorrect.
Perhaps the MAF is not working correctly and sending incorrect info to the PCM.
Perhaps the PCM's MAF table is incorrect (such as it is programmed for one of the two versions of the 3800 MAF) and that is why the PCM is operating incorrectly.

So I sent an email to fieroflyer to ask if he would have any info on the tune. Unfortunately I don't have much any info on when the PCM was tuned by him or anything. He said it would have been tuned the closest be could to the mods he was given at the time.

When I went through my pics I saw a picture of the PCM case that had sharpie marker writing on it which I could only assume is related to the tune. It's got an N (which I'm guessing would be Northstar) , LS1 (must be MAF) , 04 3800SC, and auto written on it. So as far as I can tell it's tuned properly.

Where should I go from here as far as addressing the codes?

Fort Wayne

Ya I was hoping it wouldn't have to go to someone. Can't really afford that. Would have to find a truck to barrow and rent a trailer again.

Which trouble codes are you getting now?
Did it ever run right?

What are your thoughts on swapping back to a stock 3800 throttle body which has a known MAF in it and getting a PCM programmed to match it?

Currently I'm getting the P0171 lean on bank one (which is the newest one that popped up) and the P0300 for random multiple misfire. The P0135 for the O2 heater circuit still shows up but I have not cleared that since it's being recognized now.

I don't think it has ever run right since the swap. The previous owner moved to California and couldn't take it with him. It runs much better than when I picked it up so I'm heading in the right direction. One of the soak plug wires was not all the way on and I think a couple vacuum lines were loose.

The only issue I have with swapping a stock 3800 tb back is that it's running the Gen v blower which I thought was drive by wire, so don't I need an adapter to run a regular 3800 tb?

I was going to try swapping to a stock Northstar MAF that's typically used because I have an extra Northstar tb in the garage BUT the one that's currently on the car looks totally different. I don't see how the black plastic part with the screen and MAF would attach. Can't swap tb's either because the extra one is older with the 4 bolt design compared to the 3 bolt newer style on the car.

[This message has been edited by zmcdonal (edited 08-16-2014).]

Your supercharger is like the one on the right, and you are correct it is a Gen V.



There is an adapter plate bolted to your 4 hole SC that then has the three studs screwed into it. It is the nice machined piece in your pics.

I knew there was an adapter on there, but I assumed I would need a different adapter for the 4 hole N*. Should that just bolt right up to the SC? If that's the case that would make for a slightly cleaner setup anyway.

I've never changed tb's before, what do I need to do to make it seal properly?

idk if the 4 bolt northstar throttle body will bolt up to the Gen V SC but my guess is that it won't The Gen V fly by wire throttle body has a rubber seal for a gasket. Stock GM had coolant flowing through a passage at the bottom of the throttle body. Those lines are most likely blocked by the adapter but there might still be coolant up there. Other than that it is just a 4 bolt operation.

I have a Gen V FBW TB here I can give you bolt hole measurements if you want.
------------
edit

bolt hole cl to cl

84.1 mm side to side
68.5 mm top to bottom

[This message has been edited by phonedawgz (edited 08-16-2014).]

Well I looked over it more today and got out the stethoscope to listen for vacuum leaks. I found 3 split rubber fittings so I replaced those and cleared the codes hoping for the best. When I scanned the cylinders for misfires afterwards it was still showing a lot though. No engine light so far yet though, and I let it run for a bit and started it and shut it down a few times. I also noticed that my O2 sensor seems lazy, I'm not sure if that's due to the misfires or not though but most of the time the reading stayed at 0.2v. And then would occasionally fluctuate back and forth like it's supposed to.

Well I finally figured out what was causing my p0300 code. I pulled the EGR tube, and it was cracked about 1/2 way around at the intake side, so I replaced that. Still had high misfire counts. I went out with my stethoscope and listened for injector pulse at each injector, and I ended up finding a vacuum leak at a couple of the injector o-rings. Replaces the o-rings and now 0 misfires across all cylinders.

U have a LT1/LS1 MAF and N* TB and those Mods definitely need to be accounted for in tune. U also have a Gen V to N* adapter plate which mates them together. They may already be in the tune but someone needs to check to see what has been programmed. If it ain't running right or for piece of mind.

Fixing the Vac leaks will most definitely help with the lean conditions. Great troubleshooting.

[This message has been edited by nosrac (edited 09-24-2014).]

quote Originally posted by nosrac: U have a LT1/LS1 MAF and N* TB and those Mods definitely need to be accounted for in tune. U also have a Gen V to N* adapter plate which mates them together. They may already be in the tune but someone needs to check to see what has been programmed. If it ain't running right or for piece of mind. Fixing the Vac leaks will most definitely help with the lean conditions. Great troubleshooting.

Yeah, I sent Dan, fieroflyer an email about the tune a while ago asking if he could give me any info if it was tuned for the MAF and such because he made the harness and tuned the PCM. I didn't have enough info from the previous owner about when he had it done for Dan to be able to find info on it. But it does have LS1, N*, series II, 04 3800 SC, auto, written on the case of the PCM so, I can only assume those were notes from when it was tuned. When I get home I will disconnect the battery and let the PCM start fresh and see how my fuel trims look.

[This message has been edited by zmcdonal (edited 09-24-2014).]

04 o2 sensors are not compatible with 03 and earlier pcms. Check into that being a possibility.

Ok so I finally got the car running right but the O2 heater circuit code is still popping up with the CEL and the O2 doesn't seem to be picking up data according to my torque app.

I checked for 12v power on the pink wire in the harness this afternoon and it checked out fine. Next I checked for ground on the black with white stripe wire and got nothing. So I think that's the source of my problem, however I'm not sure where to go from here.

After looking back at the previous pictures I've taken, there is a black with white stripe wire going to #37 on the PCM.


Any suggestions on what my next step should be?

You won't read a ground on the Black/White wire running to the PCM because the PCM is what grounds it. With the key off the PCM won't be grounding the wire. Maybe with the key on you might but it isn't really a good test.

With your ohm meter

Check from the Black White of the O2 sensor to the Black White wire at the PCM. You should get 0 ohms
Check from the Black White of the O2 sensor to engine ground (with the PCM connector out of the PCM) You should get infinite ohms.

Starting with a cold engine

Disconnect both connectors from the PCM. Have the O2 sensor plugged in. Key on measure the voltage on the Black/White wire.

You should get +12v. Assuming the previous test passed, then connect a ground wire to the Black/White wire (ONLY) at the PCM connector. The connectors should still be unplugged at the PCM, but the O2 sensor plugged in. Wait two minutes. Then feel the outside of the O2 sensor. It should feel a little warm.

At the O2 sensor - chech the resistance between the two wires that would connect to the Pink and the Black/White wires. This is checking on the O2 sensor connector, not the harness connector. You should read something like 5 to 10 ohms.

[This message has been edited by phonedawgz (edited 04-23-2015).]

quote Originally posted by phonedawgz: You won't read a ground on the Black/White wire running to the PCM because the PCM is what grounds it. With the key off the PCM won't be grounding the wire. Maybe with the key on you might but it isn't really a good test. With your ohm meter Check from the Black White of the O2 sensor to the Black White wire at the PCM. You should get 0 ohms

Ahh that makes sense now why I wasn't reading ground on the O2 plug.

I did check from the Black White of the O2 to the Black White at the back of the PCM today and it was reading 0.6-0.7 ohms which I have heard is within an acceptable range.

I will do the rest of the tests tomorrow, I am at work right now. I'm hoping it ends up just being a bad O2 sensor, that's an easy fix. I got a little worried that the ground didn't check out, starting thinking immediately that it was my PCM.

Thanks for the input, I really appreciate the help.

Check from the Black White of the O2 sensor to engine ground (with the PCM connector out of the PCM) You should get infinite ohms.
didn't get any reading on my meter at all.

Disconnect both connectors from the PCM. Have the O2 sensor plugged in. Key on measure the voltage on the Black/White wire.
I got 11.95v

then connect a ground wire to the Black/White wire (ONLY) at the PCM connector. The connectors should still be unplugged at the PCM, but the O2 sensor plugged in. Wait two minutes. Then feel the outside of the O2 sensor. It should feel a little warm.
O2 got hot

At the O2 sensor - chech the resistance between the two wires that would connect to the Pink and the Black/White wires. This is checking on the O2 sensor connector, not the harness connector. You should read something like 5 to 10 ohms.
I got 13.5 ohms

So it kind of sounds to me like my pcm is failing to ground the heater circuit?

[This message has been edited by zmcdonal (edited 05-01-2015).]

What I had written before was wrong

Edit

Crap idk. I will look at this more tonight when I am on the comp and not the phone.

[This message has been edited by phonedawgz (edited 05-01-2015).]

quote Originally posted by phonedawgz: O2 got hot. That means that O2 sensor heater is working. It means the wiring, o2 sensor heater, and the PCM are doing their job. Any chance this fault code is for the 2nd O2 sensor after the cat converter?

From those tests though, what tells us that the PCM is grounding the O2 heater properly? It got hot from me grounding it from the connector which tells us the wiring and sensor are working, but there's nothing telling us that the PCM is doing the same. Unless I'm missing something.

The code that keeps showing up is for bank 1 sensor 1. I can't double check it at the moment though because my bluetooth OBD2 adapter took a crap, waiting on shipping from China for my new one.

[This message has been edited by zmcdonal (edited 05-01-2015).]

quote Originally posted by zmcdonal: With everything connected key on and the O2 unscrewed from the manifold I let it sit with the key on, that O2 should get hot right, it's stone cold. Or does the car need to be physically running for the PCM to turn on the O2 heater?

It might. I can't say for sure if the PCM would have them on or off with the key on engine off. So when you said they got hot I took that to be they got hot key on engine off. Did you mean to say it got hot with the engine running? If so yeah, bolted to the manifold it will get really hot from the exhaust and what I said earlier doesn't apply.

When I said it got hot I was talking about when I manually grounded the o2 heater at the PCM connector with the key on. Key on everything plugged in, o2 stays cold.

I had thought about throwing an extra o2 that I have that has a different pigtail in the manifold to plug the hole and run the car and see if the one that's plugged in but not screwed in gets hot.

But right now I'm just going to hope the engine light stays off.

Lets start with this. Unbolt both connectors from the PCM. Using a wire stuffed into the connector side of C37 Clear (your Black/White wire from the O2 sensor) attach it to ground. Now turn the key on. Does your O2 sensor get hot like it did before? If so that means the wiring all the way to the PCM pin is good. If the O2 sensor is not getting hot then look at why there is an open between the HO2 sensor and the PCM pin.

If that worked then use a stick pin to back probe the C37 Clear. Backprobing is jamming a pin down from the back side so you can read the voltage with the connectors all hooked up. So hook up the PCM and set up your meter so you can read the voltage on C37 Clear. If the previous test passed you should be reading 0v or near on the pin when the PCM has the O2 sensor hearter turned on. This would be at start up. Once the engine has warmed up and the PCM goes into closed loop mode the PCM should be shutting off the heater and the voltage should rise to +12.

Does it do this.

ps don't kill yourself looking at the meter while driving.

I will give that a try. I watched a couple videos on YouTube about o2 heater circuits and they stated that most ecm's will shut off the heater circuit if there is a heater circuit code present, until the code is cleared making the ECM appear faulty. And they suggest clearing the code before continuing diagnostics. If that's the case it looks like I'll be waiting until my new obd2 adapter shows up from China.

quote Originally posted by zmcdonal: I will give that a try. I watched a couple videos on YouTube about o2 heater circuits and they stated that most ecm's will shut off the heater circuit if there is a heater circuit code present, until the code is cleared making the ECM appear faulty. And they suggest clearing the code before continuing diagnostics. If that's the case it looks like I'll be waiting until my new obd2 adapter shows up from China.

Hey guy I have basically the same problem, did you happen to find out anything else.