SureTrack Community Fix: Underfloor Module Corrosion

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 currently available free with the purchase of a current Snap-on® diagnostic software version or in our ShopKey Pro product.


Everyone knows that moisture infiltrating electrical components is a bad thing. So why do manufacturers continue to put them in vulnerable locations? SureTrack community member markbritt had a Chevrolet Silverado in the shop where an airbag module under the carpet was corroded causing issues and once replaced, they couldn’t get the truck to start. They posed the question to the community, and with the help of fellow community member DAG1365 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.

Vehicle
2008 Chevrolet Silverado 1500 4.8L

Title
No crank, no start, replaced ignition switch.

Complaint
Customer states that truck will not start.

Diagnostic Steps Performed/Parts Replaced
Confirmed customer’s complaint and found airbag sensing and diagnostic module (SDM) located under the rear carpet was corroded to the point of shorting the comm lines. Replaced SDM and still no crank request at PCM. Did have crank request at BCM. Replaced PCM and still no crank request. And now have stored P0633 – Theft Deterrent Key Not Programmed. All modules are communicating fine. Have reprogrammed BCM, TDM and ECM respectively. Have done multiple VTD learns through TIS. Can anyone HELP?

Best Answer from Community Member DAG1365
Would check theft module power wiring for any shorts in steering column or dash. If you unplug module does fuse blow? If not then module may be at fault, if fuse blows while unplugged have wiring short.

Cause
Ignition switch accessory circuit was shorting out.

Correction
Replaced ignition switch and fuse. Truck now starts as it should and code P0633 did not return.

Editor’s Note
General Motors issued technical service bulletins for this vehicle that covers problems with moisture causing corrosion in the airbag sensing and diagnostic module and how to address it by removing carpet padding above it.


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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.