Last year I went to Texas. As soon as I crossed the TX line, my check engine light comes on. It was code 13. Let me give you the specs on code 13, then my motor specs before I continue...

Code 13: Oxygen sensor circuit - Oxygen sensor voltage stays between 0.35 and 0.55 volts for 30 seconds when the TPS signal was above 0.55 volts. The engine had been running for at least 40 seconds with an engine temperature above 110? F.

My engine: 4.3 bored over .060, Mild Comp Cam, 350 flattop pistons, MSD Ignition and HEI distributor.

I have searched the internet over for a solution to this annoying problem and cannot find a thing!

I have ruled out bad O2 sensors by replacing 3 times in this year. I have ruled out TPS, because I replaced that as well. I have since replaced EGR, and sealed all exhaust leaks. No vacuum leaks whatsoever. I have also ruled out a bad ECU wire by following instructions in this excellent write up at: ECM Pinouts I bypassed the factory O2 circuit wire in case there was something going on with the wire. The ECM pin looked fine.

The engine did well for 3 or 4 months after the build with no trouble codes whatsoever. It only happens when I drive it. It comes on after normal operating temp is reached. And ONLY during driving. I could let it warm up and idle all day long with no code. But once the engine is under a load, it never fails to come on. I am leaning to TPS issues because of this fact.

I have also ruled out bad ECU because I installed my other ECU with the same results. I have added an Edelbrock chip, venom injectors, and injector spacers since thinking it would help with fuel, IF that were an issue, and nothing.

If ANYONE here has some advice, I would love to hear it so I could put this trouble code behind me, that would be GREATLY APPRECIATED! My truck runs great, however, that damn light is buggin the crap outta me!

I have no catalytic converter on the system, but I figured if that were an issue, I would had gotten the code when the build was first completed, and during the first few months of driving.

 

Not that anyone helped here, but... SOLVED!!!!!!!!!!!!!!!!!! I think.... Well, I looked into every possible avenue for why I was getting this code, and took every step trying to trouble shoot it... Someone in another forum mentioned my stereo amplifier, so I got to Playing around where my remote wire for the amplifier was tied to, in regards to my fuse box. Today I switched the wire over to the wiper fuse and so far, no check engine light. Previous fuses I have had it tied to were ignition, and ecm. So I take it the amp was enough to rob the o2 sensor of it's proper voltage readings, therefore causing the code 13. Anyways, Got my fingers crossed and hope this is the solution. No check engine light in the last 40 miles! WOOT!

 

its usually a good idea not to tie into the ECM fuse