Code 41 Diagnostic Procedure
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New User
Joined: Feb 2004
Posts: 2
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From: Colorado Springs, CO
Code 41 Diagnostic Procedure
I have been trying to troubleshoot my Engine Check Light problem with Continuous Code 41 (HEGO reports Lean Mixture).
Background
- Engine Check Light does not turn on until the engine warms and I drive about 10 minutes.
- The engine is running extremely rich. My gas mileage is about 15 MPG.
Troubleshooting (So Far)
1- My mechanic ran a test where he pulled the PCV. The emissions levels returned to normal and the Light turned off. His maintenance book said it was "contaminanted oil."
- I changed the oil and filter
- I cleared the trouble codes
- The Engine Check Light still turns on with Code 41
2- I replaced the O2 sensor and cleared the codes. The Engine Check Light turns on with Code 41
What should I check next? My Haynes manual does really have a good diagnostic?
-rick
Background
- Engine Check Light does not turn on until the engine warms and I drive about 10 minutes.
- The engine is running extremely rich. My gas mileage is about 15 MPG.
Troubleshooting (So Far)
1- My mechanic ran a test where he pulled the PCV. The emissions levels returned to normal and the Light turned off. His maintenance book said it was "contaminanted oil."
- I changed the oil and filter
- I cleared the trouble codes
- The Engine Check Light still turns on with Code 41
2- I replaced the O2 sensor and cleared the codes. The Engine Check Light turns on with Code 41
What should I check next? My Haynes manual does really have a good diagnostic?
-rick
Postmaster
Joined: Dec 2001
Posts: 3,742
Likes: 2
From: UT
If it were me, the next thing I'd do is go to the library and find a proper manual. Libraries around here carry Motor and Mitchell manuals. These will have complete diagnostic articles (~200 pages) that include circuit "pinpoint" tests for each code that will take you systematically through the likely causes for that code and how to troubleshoot and repair them.
That said, O2 sensor codes can be the most difficult to diagnose. 1st thing to check would be the wiring. This includes O2-PCM wires and PCM ground. Among the first thing the manuals have you check is fuel pressure. Check for exhaust leaks upstream of the O2 sensor.
That said, O2 sensor codes can be the most difficult to diagnose. 1st thing to check would be the wiring. This includes O2-PCM wires and PCM ground. Among the first thing the manuals have you check is fuel pressure. Check for exhaust leaks upstream of the O2 sensor.
