2002 3.8 Bird - Reduced Engine Power - Lots of Codes
04-29-2020, 09:36 AM
#41
11 Second Club
iTrader: (3)
Nope.. Once I seen you had one I put that job on the back burner. I've been up to my elbows in an engine swap and will be wrapping that up this week. I enjoy building engines but working on vehicles is about as bad as being
05-07-2020, 10:57 PM
#44
Did a reading on serial data circuits again, skipping other steps (for now).
I got less than half a volt and fluctuated quite a bit.
Tested multiple times and decided to test because of how the failure came back instantly after clearing the codes.
After starting to clean up, I had thought, what changed...
OBD2 scanner. So opened the door back up, pulled the scanner.
Tested again, and I got 3.X volts on both circuits!
Moved harness all over and still never changed.
Hooked back up the OBD scanner just to see some consistency. But I didnt get it... the voltage didnt drop with OBD reconnected.
Wondering if PCM is next step.
I got less than half a volt and fluctuated quite a bit.
Tested multiple times and decided to test because of how the failure came back instantly after clearing the codes.
After starting to clean up, I had thought, what changed...
OBD2 scanner. So opened the door back up, pulled the scanner.
Tested again, and I got 3.X volts on both circuits!
Moved harness all over and still never changed.
Hooked back up the OBD scanner just to see some consistency. But I didnt get it... the voltage didnt drop with OBD reconnected.
Wondering if PCM is next step.
05-08-2020, 02:28 PM
#45
Did a reading on serial data circuits again, skipping other steps (for now).
I got less than half a volt and fluctuated quite a bit.
Tested multiple times and decided to test because of how the failure came back instantly after clearing the codes.
After starting to clean up, I had thought, what changed...
OBD2 scanner. So opened the door back up, pulled the scanner.
Tested again, and I got 3.X volts on both circuits!
Moved harness all over and still never changed.
Hooked back up the OBD scanner just to see some consistency. But I didnt get it... the voltage didnt drop with OBD reconnected.
Wondering if PCM is next step.
I got less than half a volt and fluctuated quite a bit.
Tested multiple times and decided to test because of how the failure came back instantly after clearing the codes.
After starting to clean up, I had thought, what changed...
OBD2 scanner. So opened the door back up, pulled the scanner.
Tested again, and I got 3.X volts on both circuits!
Moved harness all over and still never changed.
Hooked back up the OBD scanner just to see some consistency. But I didnt get it... the voltage didnt drop with OBD reconnected.
Wondering if PCM is next step.
09-28-2020, 09:02 AM
#51
TECH Veteran
iTrader: (14)
I used to work at a nissan service garage, we had a similar issue with one getting stuck in limp mode, they through MAF's, TB, and ECM's at this thing.
finally it took a tech going through the wiring and found that a critter had chewed through a small chassis ground under the back seat affecting the ground loop of the entire Throttle control system. redid the ground and a month long issue was fixed in a bout 2 minutes and it drove home. thing got towed to us 5 times I think.
so its possible for something simple to cause systemic failures when it comes to electrical systems. its gonna be a lot of work but id start checking the grounds in the engine bay and under the dash.
you,ve thrown a lot at this thing in the way of new parts, I wouldnt give up on it yet, your problem is likely pretty simple.
have you checked the ETC fuse or the IGN relay by chance?
finally it took a tech going through the wiring and found that a critter had chewed through a small chassis ground under the back seat affecting the ground loop of the entire Throttle control system. redid the ground and a month long issue was fixed in a bout 2 minutes and it drove home. thing got towed to us 5 times I think.
so its possible for something simple to cause systemic failures when it comes to electrical systems. its gonna be a lot of work but id start checking the grounds in the engine bay and under the dash.
you,ve thrown a lot at this thing in the way of new parts, I wouldnt give up on it yet, your problem is likely pretty simple.
have you checked the ETC fuse or the IGN relay by chance?
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nimrod.sixty9 (11-12-2020)
09-28-2020, 12:56 PM
#52
I used to work at a nissan service garage, we had a similar issue with one getting stuck in limp mode, they through MAF's, TB, and ECM's at this thing.
finally it took a tech going through the wiring and found that a critter had chewed through a small chassis ground under the back seat affecting the ground loop of the entire Throttle control system. redid the ground and a month long issue was fixed in a bout 2 minutes and it drove home. thing got towed to us 5 times I think.
so its possible for something simple to cause systemic failures when it comes to electrical systems. its gonna be a lot of work but id start checking the grounds in the engine bay and under the dash.
you,ve thrown a lot at this thing in the way of new parts, I wouldnt give up on it yet, your problem is likely pretty simple.
have you checked the ETC fuse or the IGN relay by chance?
finally it took a tech going through the wiring and found that a critter had chewed through a small chassis ground under the back seat affecting the ground loop of the entire Throttle control system. redid the ground and a month long issue was fixed in a bout 2 minutes and it drove home. thing got towed to us 5 times I think.
so its possible for something simple to cause systemic failures when it comes to electrical systems. its gonna be a lot of work but id start checking the grounds in the engine bay and under the dash.
you,ve thrown a lot at this thing in the way of new parts, I wouldnt give up on it yet, your problem is likely pretty simple.
have you checked the ETC fuse or the IGN relay by chance?
MAF was cleaned.
Checked and cleaned the ground for the harness, per FSM, which was just above the AC.
Just to be clear on testing procedures, Im supposed to be checking the data leads from the TACM connector and with it unplugged right?
09-29-2020, 08:43 AM
#53
so its possible for something simple to cause systemic failures when it comes to electrical systems. its gonna be a lot of work but id start checking the grounds in the engine bay and under the dash.
you,ve thrown a lot at this thing in the way of new parts, I wouldnt give up on it yet, your problem is likely pretty simple.
you,ve thrown a lot at this thing in the way of new parts, I wouldnt give up on it yet, your problem is likely pretty simple.
09-29-2020, 09:36 AM
#54
TECH Veteran
iTrader: (14)
nimrod Id probe at the TB connector and keep the pedal assembly plugged up. that should give you proper signal values, but if I had to guess its likely a voltage supply issue for the blade actuator keeping you in limp mode. Ie its all good until the first time you try to go full pedal sweep and the blade placement doesnt match pedal placement cause the actuator isnt fully opening the TB as commanded.
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nimrod.sixty9 (11-12-2020)
11-05-2020, 11:24 PM
#55
nimrod Id probe at the TB connector and keep the pedal assembly plugged up. that should give you proper signal values, but if I had to guess its likely a voltage supply issue for the blade actuator keeping you in limp mode. Ie its all good until the first time you try to go full pedal sweep and the blade placement doesnt match pedal placement cause the actuator isnt fully opening the TB as commanded.
I'm not sure if it matters but it is not intermittent as the pedal position but intermittent like random. There are times I can drive it and it runs fantastic, no issues and can go WOT. Then other times it immediately fails and I haven't even touched the pedal.
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nimrod.sixty9 (11-12-2020)
11-07-2020, 02:09 PM
#58
So I just put the battery back in it and now I can't get it to fail.
Wiggled every harness I could reach. Firewall, PCM, TB, TACM, etc.
The intermittent is the worst about it.
I want to get this car fixed as I want to surprise my sister by giving it to her.
Her car blew up so yeah, she needs it too.
Wiggled every harness I could reach. Firewall, PCM, TB, TACM, etc.
The intermittent is the worst about it.
I want to get this car fixed as I want to surprise my sister by giving it to her.
Her car blew up so yeah, she needs it too.
Last edited by nimrod.sixty9; 11-12-2020 at 08:10 PM.
11-07-2020, 06:02 PM
#59
Could you borrow/rent a real pro level meter or oscilloscope to see if the resistance and voltages are correct? Its a long shot but if this is intermittent it might be pointing to body flex pulling on some wires somewhere causing connections to drop out of tolerance. I had a bad ignition problem once where the car would only start cold, only way to get it started after it was warm was to push start it. After weeks of pocking around the ignition system, replacing the battery and alternator, I found the issue while replacing the starter. The negative battery cable was corroded in the center and the heat generated from the car running caused the cable to swell just enough to lose contact. Scoping out each wire will be time consuming but if there are bends/kinks, corrosion, or bad connectors a scope can ID it. Definitely don't buy one as they are ridiculous expensive and super sensitive but for chasing down electrical issues in bundled wires they are the most definitive tool to find an electrical fault.
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nimrod.sixty9 (11-12-2020)
11-12-2020, 08:28 PM
#60
So I MAY have found something.
Im checking continuity between TACM and PCM harnesses.
Positive Im not doing it the 'right' way by using tiny nails to tap into the back of the TACM harness, then to cheap alligator clip wires, then to a recycled long 110v cord, then to one lead on the DMM, then other lead on DMM to PCM.
16 on the TACM goes to 14 on PCM
18 on the TACM goes to 15 on PCM
16/14 gives continuity but 18/15 does not. What I do get tho is continuity on pin 16 on the PCM harness (PCM ground).
According to the schematics I have found and the labels on this page; http://www.engine.firebirdv6.com/38pin.html
Am I doing this wrong? If not, wth is going on here?
https://i.ibb.co/W0DN6v3/sdfsdf.png
EDIT: It occurred to me as soon as I posted this, PCM ground is just that, a ground.
So I connected 18 to DMM lead, then other DMM lead to various spots on the engine, sure enough, I get continuity.
Tho I am curious as to why I still dont get it on pin 15. Figured it would be both, 15 and ground (16).
Anyway, next concern, how would this be grounded at all? I can only imagine other wires would have the same issue.
The harness that comes through the firewall is glued together in a block and isnt removable.
EDIT 2: False alarm.
Some reason, even tho nail was in pin 18 on the TACM harness, it was actually hitting pin 17.
Dont know how, but it was.
Used a needle this time and all seems normal again, like previous tests.
It did seem resistance fluctuated quite a bit, but settled around 1.3 and other at 2.5 iirc.
Im checking continuity between TACM and PCM harnesses.
Positive Im not doing it the 'right' way by using tiny nails to tap into the back of the TACM harness, then to cheap alligator clip wires, then to a recycled long 110v cord, then to one lead on the DMM, then other lead on DMM to PCM.
16 on the TACM goes to 14 on PCM
18 on the TACM goes to 15 on PCM
16/14 gives continuity but 18/15 does not. What I do get tho is continuity on pin 16 on the PCM harness (PCM ground).
According to the schematics I have found and the labels on this page; http://www.engine.firebirdv6.com/38pin.html
Am I doing this wrong? If not, wth is going on here?
https://i.ibb.co/W0DN6v3/sdfsdf.png
EDIT: It occurred to me as soon as I posted this, PCM ground is just that, a ground.
So I connected 18 to DMM lead, then other DMM lead to various spots on the engine, sure enough, I get continuity.
Tho I am curious as to why I still dont get it on pin 15. Figured it would be both, 15 and ground (16).
Anyway, next concern, how would this be grounded at all? I can only imagine other wires would have the same issue.
The harness that comes through the firewall is glued together in a block and isnt removable.
EDIT 2: False alarm.
Some reason, even tho nail was in pin 18 on the TACM harness, it was actually hitting pin 17.
Dont know how, but it was.
Used a needle this time and all seems normal again, like previous tests.
It did seem resistance fluctuated quite a bit, but settled around 1.3 and other at 2.5 iirc.
Last edited by nimrod.sixty9; 11-12-2020 at 10:09 PM.