Vehicle: 2008 Chevy Avalanche 1500, 4WD, V8-5.3L, Automatic Transmission/Transaxle

Mileage: 148,574

Problem: The Avalanche was towed in for a No crank / No start condition.

Case Details: The usual “No crank” diagnostics provided no answers, so the tech connected a scan tool and found the following diagnostic trouble codes (DTCs):

• U0122 - Lost Communication with Vehicle Dynamics Control Module
• U0199 - Lost Communication with Driver Door Control Module
• U0140 - Lost Communication with Body Control Module
• U2099 - High Speed Communication Enable Circuit

After seeing these DTCs, the technician decided to call ALLDATA Tech-Assist for some help. The Tech-Assist consultant advised that, since the technician found no communication with any module on the low speed GMLAN, he should look at the air bag module located under the driver's seat. Those modules often get corroded, causing "No crank" and "No communication" issues.

The technician inspected the air bag module as suggested and found it was indeed corroded and the carpet was still wet from rain and snow. Once he disconnected the module, GMLAN communication came back.

Confirmed Repair: After replacing the air bag module, the technician performed the required programming and dried out the carpet. The Avalanche engine cranked over normally with no further issues. Mystery solved!