2008 cobalt fault codes
June 11th, 2011, 6:12 AM
#1
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2008 cobalt fault codes
I have a problem that is causing fault codes P0036 (HO2S Bank 1 sensor 2 heater circuit), P0054 (HO2S Bank 1 sensor 2 heater resistance), and P0036P on a 2008 cobalt LT with 2.2L engine. It seems strange that I have P0036 and a pending P0036. Can any one explain what may be causing these faults. I do not want to randomly replace the O2 sensors. Any feedback is welcome.
Thanks
Al
Thanks
Al
June 11th, 2011, 9:49 AM
#2
Welcome to the forum.
The heater circuit on the O2 sensor is pretty simple. There should be an ignition voltage on the PNK/BLK wire. The ECM then grounds the GRY/WHT wire to command the heater on. P0036 says the ECM sensed an illogical state, i.e., either no voltage when the circuit is open (floating) or voltage when the circuit is closed to the ground. P0054, probably related, says the calculated resistance did not fall in the expected range (1.9-8.58 Ω, I believe). Both codes point to the O2 sensor 2. Take the connector off the O2 sensor post-catalytic converter, make sure you see 12+ V on the PNK/BLK wire with key on, engine off, and then measure the resistance across the leads that mate with the PNK/BLK wire and GRY/WHT wire. Hopefully it's just the O2 sensor itself. If still under warranty, even better.
The heater circuit on the O2 sensor is pretty simple. There should be an ignition voltage on the PNK/BLK wire. The ECM then grounds the GRY/WHT wire to command the heater on. P0036 says the ECM sensed an illogical state, i.e., either no voltage when the circuit is open (floating) or voltage when the circuit is closed to the ground. P0054, probably related, says the calculated resistance did not fall in the expected range (1.9-8.58 Ω, I believe). Both codes point to the O2 sensor 2. Take the connector off the O2 sensor post-catalytic converter, make sure you see 12+ V on the PNK/BLK wire with key on, engine off, and then measure the resistance across the leads that mate with the PNK/BLK wire and GRY/WHT wire. Hopefully it's just the O2 sensor itself. If still under warranty, even better.
June 14th, 2011, 11:56 AM
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Thanks again. I did measure resistance on O2 sensor and have an open circuit. I couldn't get my arm snaked down behind the engine to attach leads to the connector leading to the ECM to verify 12v, but feel pretty good that it's probably not loss of votage. The connector housing leading to ECM is rigidly attached to another structure and I didn't want to risk breaking the connector to try to detach it. Ordered new sensor and hopefully it will resolve the problem. I have to be out of town so it will be saturday before I'll know.
I'll post update this weekend.
I'll post update this weekend.
June 18th, 2011, 8:56 AM
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Thank you for the excellent information. As I said previously I measured open circuit on the O2 sensor. I replaced the sensor yesterday and the car has been driven over 200 miles with no problem reported.
Thanks Again
Al
Thank you for the excellent information. As I said previously I measured open circuit on the O2 sensor. I replaced the sensor yesterday and the car has been driven over 200 miles with no problem reported.
Thanks Again
Al
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