Help with DTCs

Ray Mier · June 14, 2023

Hello,

I have a 2000 Silverado 2500 with the LQ4. I have attached a pdf with all of my trouble codes. I was wondering if anyone had any experience with similar issues. The instrument cluster works but the oil gauge is a little jittery, I replaced the sending unit and it’s still the same. It has a rough idle and I tested for vacuum leaks, didn’t have any. I replaced the fuel regulating valve because the was fuel in the vacuum tube, still has a rough idle. The brake ABS light is also on. Could this be a problem with the ECM?

S3.pdf

asilverblazer · June 14, 2023

I'd focus on O2 sensors and knock sensors.

Inspect the brake light switch and clean its internals if needed.

Clear the codes and see what comes back.

I don't see anything indicating a bad ECM yet.

Edited June 14, 2023 by asilverblazer

bubbanbrenda · June 14, 2023

I agree replacing all of the o2 sensors will likely fix most if not all of the engine codes. Ordinarily “lost communication” with a control module means the module has failed, but with so many different lost communication codes, and the low voltage I would look for bad grounds and or alternator connections.

swathdiver · June 15, 2023

14 hours ago, Ray Mier said:

Hello,

I have a 2000 Silverado 2500 with the LQ4. I have attached a pdf with all of my trouble codes. I was wondering if anyone had any experience with similar issues. The instrument cluster works but the oil gauge is a little jittery, I replaced the sending unit and it’s still the same. It has a rough idle and I tested for vacuum leaks, didn’t have any. I replaced the fuel regulating valve because the was fuel in the vacuum tube, still has a rough idle. The brake ABS light is also on. Could this be a problem with the ECM?

S3.pdf 22.83 kB · 7 downloads

Sign up for the shop manual at ALLDATADIY and follow the troubleshooting guide for the O2 sensor codes. Avoid the temptation to throw parts at the car, gets expensive quick especially when 4 GM sensors are nearly $200.

Aftermarket sensors don't play nice with the computer system.