O2 sensor heater circuit
Senior User
Joined: Sep 2003
Posts: 223
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From: York, PA
I'm going to chime in here, Fuel pressure on this 1996 engine is 45-60 PSI key on engine running, closer to 45 with vacuum on the fuel regulator, and closer to 60 with the vacuum line off the fuel regulator running. 50-60 key on engine off.
P0136 says HO2S-12 no activity circuit conditions: Engine running in closed loop for 5 minutes, then the PCM detected that the HO2s failed the maximum or minimum voltage range check (middle signal out-of-range)(which means: oxygen sensor is not crossing the 450 millivolt range) note which oxygen sensor here that code 136 is talking about, the sensor behind the catalytic converter, not in the exhaust manifold. This is not a heater circuit issue, but a oxygen sensor performance issue, could be staying high, above the 450 millivolt range or it could be low, under the 450 millivolt range, the sensor performance is just not crossing the middle of the sensor calibration area. I would backprobe the sensor wire and test the sensor or remove the sensor, mount the sensor in a bench vice lightly, hookup the meter to the sensor and send a propane torch lightly over the sensor and check the ability to cross the 450 millivolt range consitently for starters. If the sensor works, check wiring to PCM, backprobe PCM wiring at PCM, retest O2 performance, if O2 is not working, replace O2.
Hope this helps, broken wire
P0136 says HO2S-12 no activity circuit conditions: Engine running in closed loop for 5 minutes, then the PCM detected that the HO2s failed the maximum or minimum voltage range check (middle signal out-of-range)(which means: oxygen sensor is not crossing the 450 millivolt range) note which oxygen sensor here that code 136 is talking about, the sensor behind the catalytic converter, not in the exhaust manifold. This is not a heater circuit issue, but a oxygen sensor performance issue, could be staying high, above the 450 millivolt range or it could be low, under the 450 millivolt range, the sensor performance is just not crossing the middle of the sensor calibration area. I would backprobe the sensor wire and test the sensor or remove the sensor, mount the sensor in a bench vice lightly, hookup the meter to the sensor and send a propane torch lightly over the sensor and check the ability to cross the 450 millivolt range consitently for starters. If the sensor works, check wiring to PCM, backprobe PCM wiring at PCM, retest O2 performance, if O2 is not working, replace O2.
Hope this helps, broken wire
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