(Not Festiva) Possible wiring, or ECU problem with 2002 Cavalier LS Sport

[TorqueEffect]

Sorry, this isn't a Festiva, but nobody seems to want to bother to respond to my issue over on the J-Body forum.

But this is a 2002 Chevy Cavalier LS Sport

2.2 Ecotec with 4 Speed Automatic with 109k miles

The check engine light is on, and I pulled code P0327 (Knock Sensor Low input voltage) and P0507 (Idle control system RPM higher than expected), and just today I pulled a code for a hard "Running too lean" code


Now the speedo needle has been randomly dropping to 0, and when this happens the transmission will stick in first gear. Here is a video I recorded today on the way to work.

https://youtu.be/aZTtiPdtdwc

Also the Trac Off light keeps coming on, and going off multiple times in a short drive as well.

Just and FYI. This car HAS in the past been totaled, and rebuilt, and inspected and approved for a Rebuilt title. Apparently from the previous owner, they said the whole front clip of the car was replaced.
It wouldn't surprise me if the ECU might have been damaged in the crash that totaled it. I found on google that 3rd Gen J Body ECU failure is quite common. But I am reluctant to replace it, since it requires Tech2 programming.

But I am also concerned that it may be the engine wire harness, since sometimes the car runs perfectly, and other times it runs like complete crap. It's never failed to start, and always starts on the first crank.

What do you guys think?

PS. Also getting AWFUL gas mileage. like the car has only done less than 200miles on this tank and is at between and eighth of a tank, and a quarter.

[FestYboy]

Start inspecting for a vacuum leak. If you have a scan tool that has live data, check the long term fuel trim. Those intakes are known to leak. That would explain the last 2 codes and poor mileage. The knock sensor has just likely failed.

As for the traction light, inspect the tone rings on your front axles for cracks. They are SMALL. It may not be big enough to activate the abs but the bcm may see it as wheel spin.

[TorqueEffect]

But why would a vacuum leak make the ecu go completely haywire and think i'm not moving when going 30?

Watch the video if you haven't.

[jwt101]

I had a 2002 sunfire did the same thing. The speedo sensor was failing. I changed that and also changed the motors on the gauges themselves as they are know to be bad and do random stuff. Easy and quick and cheap if you do it yourself. You might also check your abs speed sensor wiring since it is tripping the trac light.

[FestYboy]

Yeah I kinda ignored the speedo issue as that's a known problem with that generation of GM.

[FestYboy]

But why would a vacuum leak make the ecu go completely haywire and think i'm not moving when going 30?

Watch the video if you haven't.

The vac leak has nothing to do with the speedo. I'm more worried about the codes it's throwing.

[TorqueEffect]

Alright, thanks guys, really appreciate the help.

I guess I will start replacing sensors then, and looking for the vacuum leak. lol

[shorestiva]

If you don't find a problem with the tone rings. I'd suspect a break in one of the wires for the front abs sensors. Another common gm problem. I've never seen a abs problem cause one to stick in gear like that though. Pull your transmission wiring connector (round 20 pin connector) and check for transmission fluid in it. I'm running into work here shortly I'll look up a few things when I get there.

[TorqueEffect]

Something is seriously wrong now, speedometer doesn't work at all now, it stalls all the time at stops unless you shift into neutral. There is random engine tapping under certain engine loads. And now the ecm gives a code for idle high, knock sensor low input, transmission speed sensor low input, lean code and o2 sensor code.

I've inspected the wiring the best i could without unraveling the harness, and there is no breakages or signs of burnt or shorting wires. Unplugged all the connectors i could find and cleaned then. Was no better. None of them were corroded or had fluid on them.

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[firebush357]

I had all kinds of problems with a Dodge Caravan once and it ended up being the ECU itself had gone bad. Whenever it would get to operating temperatures it would start freaking out. After about $300 at a family mechanic, I ended up pulling a new ECU from a junkyard for like $75 and everything worked fine.

[TorqueEffect]

yeah, once I have the money, I am going to order an ecu online that is preflashed to my vin.

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[tooldude]

It might be a good idea to check battery/alternator voltage and for proper B+ and grounding at the PCM before you condemn it since some sensor inputs are reporting low. Idk if this will work on your car, but before throwing sensors at the problem, you could try unplugging the wheel speed sensors and TSS and see if you drop the other codes. Some very erratic signals might be affecting the PCM.

[FestYboy]

Torque, did you look up the live data pids? Without knowing what the ECU is seeing, you can't condemn it

[TorqueEffect]

so probe the ecu live data wires at the ecu with a multimeter? you mean the sensor wires at the ecu?

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[shorestiva]

edit. ... never mind read that wrong