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stuck in open loop and LTFTs pegged at 0.0%

F

fst

New member
What would cause the pcm stay remain or get stuck in Open-Loop mode? Im having an issue when I got my car back that the PCM is showing its running in open-loop. I scanned and checked via the LS1M. at first I thought it was because I accidentally, rather the mechanic, accidentally didn’t tighten the wiring harness for the B1S1 o2 sensor so it touched and got burnt against the rear header. ‘no problem’ I thought, so I limped the car home and took the wiring harness for the o2 sensor out and cut the section burnt and resoldered the ends again(never had a problem soldering the wires for the o2 sensor).

After everything was reinstalled, I also resetted the pcm via the powrtuner by doing a partial write. Waited 20 seconds and started the car up. Scanned via LS1M and the pcm still showed open-loop. I took the car for a short test drive and noticed anything over 10% throttle, my fuel pressure gauge went from the normal ~45psi to 100%psi ??? my WB was jumping around and checking my LS1M, the O2s were bouncing like normal, the IPWs didn’t drastically spike in relation to the fuel pressure gauge, BUT my LTFTs stayed at 0.0%???? I can only imagine driving like this would give me very bad mileage. Anything for me to doublecheck in case the mechanic forgot to reinstall a wiring harness or something else?:th_scratchhead::th_wtf:
 


Check your coolant temp sensor, there are two side, so the dash gauge may show ok, but the PCM wont see it, you can check this with your LS1M..... Also, may have fugged something in the o2 sensor circuit in the pcm... and look for a ground issue with your gauge, when your at WOT the engine moves alittle, and this my be causing the spike to 100psi
 
thanks for the suggestion o2bluegt however i guess resoldering the o2 sensor didnt do a difference cause the P0134 code came back which is something like No activity frmo B1S1. im gonna go to pep boys/advanced auto and get another ac delco o2 sensor >.<
 
not to state the obviouse but did you solder the correct wires back? in other words did you switch the 2 up by accident??
 
The sensor itself may have been damaged when the harness was burnt. Probably best to just replace the whole piece.
 
^^^ good point, if the heater side shorted to the sensor side, I imagine it would destroy the unit pretty quick
 


A buddy of mine just had that happen to him (wire melting on the header) and all he did was just solder them back and it was good...guess he is an exceptionn to the rule lol or just got lucky :th_winking:
 
I would lean toward an internal PCM problem due to the harness shorting on the exhaust. Good luck and let us know.
 
FYI-turned out the wires was still bad on the O2 sensor, i swapped the O2 sensor with a spare i had and it works fine now. thanks guys
 
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