SureTrack Community Fix: Bad Mix

Real Fixes from the SureTrack® expert information resource are documented issues from actual shop repair records and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is available at no additional cost in our ProDemand product.

Having a new trouble code after you do repairs, and there are no symptoms, can be frustrating? SureTrack community member germanautorepairM had a BMW 335i in the shop that they repaired a misfire situation but now have a code 29E0 (P0171). They posed the question to the community, and with the help of fellow community member BMWTECH and others, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

2008 BMW 335i 3.0L

Fault code 29E0 (P0171), replaced mismatched fuel injectors

Check engine light on and code 29E0 after repairs.

Diagnostic Steps Performed/Parts Replaced
First repair was replacement of the DME (Digital Motor Electronics) due to failed drivers for fuel injectors 4,5 and 6. Replaced said injectors as well, then replaced valve cover due to faulty PCV. Car runs fine just sets the 29E0 (P0171) fault. Performed a smoke test and no leaks were found. Bank 1 mutliplictave at idle is at 22.1 and bank 2 is at -2.9 to 3.8. Would injectors 1, 2 and 3 cause this fault? Causing a lean fault with bank 1?

Best Answer from Community Member BMWTECH
What are the index number on 1, 2 and 3 injectors? The ones you just replaced on 4,5 and 6 should be 12. Are they? You can not mix index 12 injectors with anything lower than 11. It is possible that index 11 and 12 injectors are better flowing than previous injectors. If it was me, I would swap bank 1 and 2 upstream O2 sensors. If it doesn’t follow the O2, then I would replace the other 3 injectors.

Swapped O2 sensors and numbers did follow to the opposite side, indicating that 1, 2 and 3 injectors with a different index from the new ones on the other bank are causing the problem.

Replaced fuel injectors 1, 2 and 3 and then rechecked the bank one mutlipictaves and the numbers are where the should be at. Check engine light no longer comes on and code did not return. Thanks for everyone’s help.

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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.