would stay in open loop....cleared code and now goes into closed loop until code is set.post cat 02 reads bias voltage koeo......after running for a little it goes to 1024 mv.02 sensor was replaced previously.stft goes to -27 under load.i was thinking of high fuel pressure or leaking injectors.thinking of checking fuel pressure and doing an injector drop test.rich condition causing high post cat voltage.anyone run into this before?thanks.
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Heater shorted to the signal? Seen it in Jeeps. Runs OK until it hits closed loop then drives it lean because of excessive voltage at the signal. Jeeps will read ~ 2 volts, as it is all the PCM is programmed to read. GM may limit is to 1.02.
Basically, see if it is going to closed loop and this is occurring right away. Also, look at the pre and post cat info. If the upstream is really going full rich, expect the downstream to follow suit if the vehicle is being driven full rich. The cat will saturate with fuel in a short time, and the downstream will let you know this is occurring. If the upstream drives full rich and the downstream goes lean, it is an issue within the sensor, as the cat will saturate with O2. If both are driving in the same direction then your O2s are likely reading correctly. -
thanks for reply....new 02 bosch oe.looked at bias voltage on solus pro and 450 mv. koeo and after starting car voltage climbs......pre cat 02 switching normally.Comment
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I think its time to look at pcm. pull o2 wire out @ pcm and run it. watch circut voltage on ckt w/ voltmeter and watch data. if voltmeteris reading screwy still, its not in ecm- engine timing or oil burning is where i'd go.
if the pcm data stills shows screwy and voltmeter normal stuff, pcm powers/grounds ok then pcm needs replacementComment
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Meh. I am not a fan of Bosch. Seen too many GMs unhappy with their O2 sensors. I would drop an NTK or Denso in it.
You can disconnect the O2 and look at the voltage at the sensor, then compare it at the ECM, but I suspect the sensor is just junk.
You can remove the heater fuse and see if the sensor continues to act the same way, but I bet it doesn't.Comment
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