Symptom
An Electronic Control Module (ECM) reset occurs when the ECM momentarily reboots or is turned OFF and ON while the engine is operating. Symptoms of this include the following:
• Wait to start lamp cycles ON while engine running
• Engine stumbles and may die
• Loss of accelerator pedal authority
• Miles driven are not logged if ECM reset occurs during current key cycle
If a reset occurs, the engine will momentarily stumble and the ECM will go through a normal KEY ON cycle.
This includes the following:
• Illuminate the WAIT TO START lamp
• Validate the accelerator pedal position
If the pedal is not at idle position when the reset occurs, a DTC is set and engine speed goes to low idle. The ECM will not allow accelerator pedal authority until the Accelerator Pedal Sensor (APS) is released.
An Injector Drive Module (IDM) reset will occur if power is lost to the circuits for IDM Logic or IDM Main
Power while the engine is operating. If power is lost, the engine will miss and recover or stall. The APS will
not be affected by this fault.
Cause
Momentary loss of power to the ECM or IDM may be caused by the following:
• Failed fuses
• Intermittent open circuit
• Failed battery power feed harness
• Poor ground connection
• Failed power relay
• Shorted or open harness
Procedure
1.Using the EST, check for DTCs for both the engine and chassis modules.
• If DTC 626 (unexpected reset fault) or 534 (IDM relay voltage low) are present as active or inactive codes, continue with next step.
• If any other engine DTCs are active, perform appropriate diagnostics and repairs before continuing with these procedures.
• If any chassis DTCs are active when checking the Electronic System Controller (ESC), perform appropriate diagnostics and repairs before continuing.
NOTE: See Section 7 in this manual, the Chassis Electrical Circuit Diagram Manual and Electrical System Troubleshooting Guide for the model and year of the vehicle when performing the following steps.
2. Check all ECM and IDM related fuses.
3. Check all Battery, VIGN and ground connections for the ECM and IDM.
4. Monitor ECM powers and grounds with breakout box under operator complaint conditions.
5. Monitor IDM powers and grounds with 12-pin Breakout Harness under operator complaint conditions.
6. If root cause has not been identified in previous steps, continue diagnosis by performing the remaining steps on the Performance Diagnostics form or Section 6 of this manual.
