Transmission or ECM?

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daveypantele

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Okay so heres the time line....

Driving a (stock) 2002 Chevy Tahoe Z71 Flexfuel

A couple weeks ago I had a code and when scanned I got p0463 (Fuel Level Sensor "A" Circuit High). Let it be noted that my fuel level gauge has never worked properly. I just fill up every 250 miles to be safe.


I had the code cleared and a few days later I drove about an hour down the freeway and everything was fine, traffic was great. When I exchanged freeways, I had to come to a dead stop. Upon attempting to accelerate again, my truck didn't want to move. It was almost like driving a standard and trying to take off in 3rd or 4th gear. After a few seconds, she took off and this became an intermittent issue over the next few days, usually temporarily resolved by doing a reset via the negative cable. When it threw a light again, I scanned it and about 10 different codes showed up. Everything from a bad brake light switch to the same p0463. Others included...

p0171 (System too Lean Bank 1)
u1000 (Critical Operating Parameter)
p0200 (Injector Circuit/Open)

I don't remember the others, but since a few seemed bogus, such as the brake light switch and ABS, I just reset the computer and everything seemed fine after that. I went ahead and replaced the fuel filter, and the acceleration issue I had went away.

I kept getting a lean code so I fixed the exhaust leak I had at the manifold/Y pipe flange on bank 1 driver side. But! And here's where my real problem is.

On my way to the muffler shop two days ago, my truck would not shift beyond 2nd gear, even manually. The code read p0757 (Shift Solenoid B Stock On). I got the exhaust fixed and came home. Yesterday I got another code for Throttle Position Sensor Low Voltage (which is only a month old). I unplugged it and plugged it back in, idle dropped to normal (approx 600) from 1,000 rpms and code went away. Today I replaced both of the solenoids, new filter and fluid, and still no shifting out of 2nd. Its like its in limp mode. I haven't driven enough to find any more codes.

Any ideas!?
 

sumo

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Multiple problems. I'd say check your battery cables. Could have a bad or corroded terminal. Those are too random of codes and for you to replace a code for solenoid and still have no movement clearly makes me believe it's a ground issue.
 
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daveypantele

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Any idea where I can find a diagram to show me where all the ground locations are?
 

sumo

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Any idea where I can find a diagram to show me where all the ground locations are?

Easiest is check battery terminals for loose or corrosion. Then check battery negative cable and check where it grounds
 

M1Gunner

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Okay so heres the time line....

Driving a (stock) 2002 Chevy Tahoe Z71 Flexfuel

A couple weeks ago I had a code and when scanned I got p0463 (Fuel Level Sensor "A" Circuit High). Let it be noted that my fuel level gauge has never worked properly. I just fill up every 250 miles to be safe.


I had the code cleared and a few days later I drove about an hour down the freeway and everything was fine, traffic was great. When I exchanged freeways, I had to come to a dead stop. Upon attempting to accelerate again, my truck didn't want to move. It was almost like driving a standard and trying to take off in 3rd or 4th gear. After a few seconds, she took off and this became an intermittent issue over the next few days, usually temporarily resolved by doing a reset via the negative cable. When it threw a light again, I scanned it and about 10 different codes showed up. Everything from a bad brake light switch to the same p0463. Others included...

p0171 (System too Lean Bank 1)
u1000 (Critical Operating Parameter)
p0200 (Injector Circuit/Open)

I don't remember the others, but since a few seemed bogus, such as the brake light switch and ABS, I just reset the computer and everything seemed fine after that. I went ahead and replaced the fuel filter, and the acceleration issue I had went away.

I kept getting a lean code so I fixed the exhaust leak I had at the manifold/Y pipe flange on bank 1 driver side. But! And here's where my real problem is.

On my way to the muffler shop two days ago, my truck would not shift beyond 2nd gear, even manually. The code read p0757 (Shift Solenoid B Stock On). I got the exhaust fixed and came home. Yesterday I got another code for Throttle Position Sensor Low Voltage (which is only a month old). I unplugged it and plugged it back in, idle dropped to normal (approx 600) from 1,000 rpms and code went away. Today I replaced both of the solenoids, new filter and fluid, and still no shifting out of 2nd. Its like its in limp mode. I haven't driven enough to find any more codes.

Any ideas!?

Like the others who responded. I would check grounds. Also any connectors that may be in common with these components. If any major work has been done remotely close to a common ground or harness connection may have knocked something loose. These situations are extremely difficult next to impossible to help diagnose without physically being there. If you are suspect of a computer malfunction sometimes a good bump with the bottom of your fist will expose that. This especially was true with older Dodge pickups. I actually recorded a video of this. I would bump the PCM and you could hear the Evap purge solenoid start going crazy.

Any way here's the ground distribution schematics you asked for (02 4WD 5.3 Flex) i assumed it was 4wd since you said z71. I'm fortunate enough to have access to this information so I try to share the wealth when I can.

GOOD LUCK!

IMG_2859.PNG

IMG_2860.PNG

IMG_2861.PNG

IMG_2862.PNG
 
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daveypantele

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New developments. Last night I caught a real bad misfire. Codes p0200 and p0302. Checked the harness to the injector, coil, and the plug wire, all seemed fine. Reset and misfire went away. Plugs are less than 6 months so I didn't bother to pull them. Haven't gotten to checking the grounds from the diagrams Gunner sent. I'll do that after work today. But that's the second time that misfire code sequence has happened. It happened initially when it went biserk and showed that afformentioned plethora of codes. Could this be related? Theoretically, could a bad plug wire cause this limp mode issue? Or a clogged injector? Bad coil?
 

VA929RR

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My $.02.... Wayyyyyy to may issues and random codes for there NOT to be an electrical issue... Before I'd change a light bulb, I'd change the battery...

You have a battery or ground issue... ‍♂️♂️


Sent from my iPhone using Tapatalk Pro
 

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