238 6 PERFORMANCE DIAGNOSTICS
• If ICP is still high or unstable, replace IPR
following procedures in Engine Service
Manual and retest.
Possible Causes
• Low injection control pressure
• Injection control pressure system leakage
• Failed IPR wiring (power and control)
• Failed IPR valve
• Failed injector
• Cracked or porous high-pressure rail
• Injector oil inlet adapter O-rings
• Injector oil inlet adapter
• O-ring for high-pressure oil rail
• End plugs in high-pressure oil rail
• Low oil pressure
• Inoperative high-pressure oil pump
• Failed ICP sensor circuit
• Failed ICP sensor
• Inoperative brake shut-off valve of Diamond
Logic® engine brake
• Brake pressure relief valve (optional)
If relief valve is leaking, the brake shut-off
valve is suspect.
• If ECM detect low boost pressure, an
incorrect feedback signal from A PS or the
ICP sensor, the ECM commands the IPR
valve to reduce injection control pressure.
• High injection control pressure
• Aerated lube oil
• Bias high ICP sensor – low duty cycle
• Erratic injection control p ressure
• ICP sensor
•IPRwiring
•IPRvalve
• Middle seal IPR valve
• Brake control pressure
• Failed BCP sensor circuit
• Failed BCP sensor
• Inoperative brake shut-off valve of Diamond
Logic® engine brake
• Brake control pressure system leakage
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any proced ures.
Follow all warnings, cautions, and notes.
©August 2008 Navistar, Inc.
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