4 ENGIN E SY M PTOMS DIAGNOSTICS 113
ECM Reset / IDM Reset (intermittent engine
stumble)
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 a uthority
• Miles driven are not logged if ECM reset occurs
during current key cycle
If a reset occu rs, the engin e will mom entarily stumble
and the ECM will go through a normal KEY ON cycle.
This includes the following:
• Illuminate th e WAIT TO S TART lamp
• Validate the accelerator pedal position
If the pedal is not at idle po sition 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 s tall. 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 Electro nic System C ontroller (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, V
IGN
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.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
To Next Page
Loading...
Need help?
General