Rear O2 Sensor
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Joined: May 2013
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2006 E350 4MATIC
Rear O2 Sensor
2006 E350 4Matic, Check Engine light will not go away. The codes are for the rear O2 sensors which I had replaced. After 50 miles of driving, the Check Engine light came back on with the same code for the Rear O2 sensor. Validated the harness and validated that the O2 senor is functioning. But Check Engine light keeps coming back. Any suggestions as to what the issue can be or has anyone else had this issue?
Thank You
Thank You
Member
Joined: Jan 2012
Posts: 244
Likes: 4
From: PA, USA
2004 E320 4matic Sedan
I agree with the steps you've taken so far....
P0038: HO2S heater control circuit high (bank 1, rear sensor)
P0141: O2 sensor heater circuit malfunction (bank 1, rear sensor)
Sorry, I don't have the answer for you. You seem to have taken the correct first steps.
Since you have already replaced the O2 sensor, let's assume for now that the new and old were actually both OK in themselves.
For the benefit of others, it appears that your O2 sensors heater wires are either not grounding well or not getting voltage. I am presuming the former, since code 38 means the circuit is high. But you do say you've checked the harness.
I can only suggest that you take your multimeter again and check for voltage on the four wires. With ignition on, engine off, I expect you should see 12 volts on one of the contacts, being the power to the heater. I don't know which contact that will be, as I do not have a wiring diagram nor can I tell you which the ground wire is. I do suspect it is the ground wire that is not continuous and perhaps you could trace that visually to see what you see.
Apologies if my suggestions are stating something obvious to you.
P0141: O2 sensor heater circuit malfunction (bank 1, rear sensor)
Sorry, I don't have the answer for you. You seem to have taken the correct first steps.
Since you have already replaced the O2 sensor, let's assume for now that the new and old were actually both OK in themselves.
For the benefit of others, it appears that your O2 sensors heater wires are either not grounding well or not getting voltage. I am presuming the former, since code 38 means the circuit is high. But you do say you've checked the harness.
I can only suggest that you take your multimeter again and check for voltage on the four wires. With ignition on, engine off, I expect you should see 12 volts on one of the contacts, being the power to the heater. I don't know which contact that will be, as I do not have a wiring diagram nor can I tell you which the ground wire is. I do suspect it is the ground wire that is not continuous and perhaps you could trace that visually to see what you see.
Apologies if my suggestions are stating something obvious to you.
