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Has anyone ever come across a vehicle that refuses to come out of open loop. This 02 Avalanche I came across today that has multiple misfires out of both banks, and is running rich (14 ltft from both banks). Engine coolant 175 degrees. Any ideas?
There have to be met various criterias for the pcm in order to enter closed loop. If this does not happen it could be something very basic like a broken O2 sensor.
Check the service information for closed loop enabling criterias and look for what's missing. Consistent misfires may well be your problem!
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Last edit: 7 years 3 months ago by juergen.scholl.
I agree with Juergen, it could be that one of your faults (running rich, misfires, ect.) is preventing the PCM from entering closed loop. Lying temperature sensors are another possibility.
I have seen coolant sensor circuit issues causing the engine to stay in open loop, if the engine computer is not seeing expected readings from the coolant sensor it substitutes a default value and stays open loop. Same would apply to some other sensors ie MAP or MAF.
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