474 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
WARNING: To avoid serious personal injury, possible death, or damage to the engine or vehicle,
when performing ICP system checks and tests – comply with the following:
• Read all safety instructions in the foreword of this manual. Follow all warnings, cautions, and
notes.
• When running the engine in the service bay, make sure the parking brake is set, the transmission
is in neutral, and the wheels are blocked.
• Be careful to avoid rotating parts (belts and fan) and hot engine surfaces.
DTC 331 – ICP above system working range
DTC 331 is set by the ECM when the injection control pressure is above normal working range of 30 MPa
(4351 psi) for 1.5 seconds. DTC 331 can be an indicator of a problem in the mechanical injection control
pressure system, wiring, or ICP sensor.
When DTC 331 is active, the ECM will ignore feedback from the ICP sensor and control the IPR valve from
programme d d efault values. The amber ENGINE lamp will be illuminated when D T C 3 3 1 is ac tiv e.
Possible causes for DTC 331 inc lud e the following:
• Debris in engine
• Incorrect grade of oil
• Inoperative, stuck or plugged inlet on the IPR valve
• IPR control wire shorted to ground
• ICP sensor or circuit causing signal to be biased high
Checks and Tests Comment
Check oil level and quality. Check oil level and for contamination, debris, and correct API
classification.
Check active and inactive DTCs. Repair any ICP sensor codes. See “ICP Sensor” (page 457).
Do ICP Operational Voltage Checks. Check KOEO pressure sensor value and voltage
.See“ICP
Sensor” (page 457).
Do IPR Pin-Point Diagnostics.
See “IPR” (page 494).
Do the KOEO Standard Test. Test will verify IPR valve circuit continuity. See “Performance
Diagnostics” – Section 6 (page 205).
Do KOER Standard Test and Injection
Control Pressure Test.
See “Performance Diagnostics” – Sect
ion 6 (page 205).
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.
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