Can anyone please tell me in detail what happens when the PCM goes into limp mode? Like when the O2 sensors are unplugged, or when the SES light comes on and the car runs off pre-programmed fuel maps. Does anyone know which sensors are still used and which ones are ignored?

Thanks
Matt

 

bump...

 

It depends what you mean by limp mode, and it depends which sensor is no longer functioning. Unplug the O2s and I wouldn't say the PCM goes into limp home, just open loop all the time. Unplug the MAF, and it's running in speed density, but again, I wouldn't say limp home. Limp home would be more like unplugging the MAF and MAP, O2s, coolant temp sensor, and trying to drive the car with just the TPS. Maybe someone else knows exactly what limp home means as it applies to the '8051 (or other f-body PCM).

 

My Blazer went into limp mode and had no power at all a total dog. It was winter and alot of snow on the ground and truck wouldnt spin the tires in the snow much at all I thought the wife blew the tranny. Till I seen the SES light took to Autozone they reset it and drove fine. This was from my remote start acting up.

 

Ok sorry for the incorrect terminology. I'm talking about open loop (if that's what it is when I unplug the O2's). I noticed today that the car does not stumble or idle rough when it was cold (in open loop). So, which sensors AREN'T used in open loop that are in closed loop (besides the O2's)?

TIA
Matt

 

O2s are the only ones. Everything else is used all the time, regardless of open or closed loop mode.