U0400 GMC – Invalid Data Received

U0400 GMC Possible Symptoms

Engine Light ON (or Service Engine Soon Warning Light)

U0400 GMC Possible Causes

Faulty Engine Control Module (ECM),Engine Control Module harness is open or shorted,Engine Control Module circuit poor electrical connection,Engine Control Module (ECM) not configured

U0400 GMC Description

Some control modules are constantly receiving information from other control modules through serial data communication network. The invalid data code will be set when a receiving control module detects a discrepancy in information it receives from another control module causing its integrity to be questioned. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.