SureTrack Community Fix: Not an EVAP Leak

Real Fixes from the SureTrack® expert information resource are documented issues from actual shop repair orders 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 currently available free with the purchase of a current Snap-on® diagnostic software version.

Sometimes a customer thinks they know what’s wrong with their vehicle when they bring it into your shop, but that can just be a distraction. SureTrack community member bmaples had a Chevrolet Silverado in the shop where the customer thought they had an EVAP leak but it was something else. They posed the question to the community, and with the help of fellow community member Ericsautomotive 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.

2006 Chevrolet Silverado 1500 4.3L

Check engine light on, several codes, repaired chafed wire.

Customer complains that check engine light is on.

Diagnostic Steps Performed/Parts Replaced
CEL with multiple other codes stored. Came in for a supposed EVAP leak problem but there is a more pressing issue. Scan revealed multiple codes and are listed in order as they show on the Zeus. P0036, P0054, P0056, P0060, P0141 and P0161 all for downstream O2 sensors. P0171, P0300, P0442 and P0455 for EVAP small and large leak. Cleared codes and the P0036 and P0056 come back immediately. KOEO all 4 O2 sensors sit at around 400 MV. Checked and found the fuse for the downstream sensors blown and it blows immediately once key is turned back on. Unplugged both sensors and fuse still blows. Hooked test light to B+ and touched other end to the load side of the fuse cavity and it lights indicating a dead short. Hoping someone has seen this before and can give some insight. Shouldn’t the sensor be sitting at 0 with KOEO? Could this be because of the short? I figured the next step would be to try and isolate the circuit at the mid point and go from there. Any tips or guidance is greatly appreciated.

Best Answer from Community Member Ericsautomotive
Check harness for chafing atop the transmission. Seen it many times.

Found chafed pink IGN feed wire grounding out up near the bell housing.

Repaired pink IGN feed for O2 sensors. Cleared codes and test drove vehicle. Check engine light off and codes did not return.

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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.