476 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
Do Injection Control Pressure Test. Verify if oil is aerated at high idle. See “Performance Diagnostics”
– Section 6 (page 205).
Test ICP system for leaks. See “Hard Start and No Start Diagnostics” – Section 5 (page 143).
DTC 334 – ICP unable to achieve set point in time (poor performance)
DTC 334 indicates an injection control system response time fault an
d may be set during normal engine
operation through the continuous monitor function or during the KO
ER Standard Test.
DTC 334 compares measured ICP to desired ICP and looks for a la
rgepressuredifferenceof9.5MPa
(1378 psi) for a period of 3 seconds.
When DTC 334 is active, the ECM ignores the ICP sensor and cont
rols the IPR valve operation from
programmed default values.
Possible causes for DTC 334 inc lud e the following:
• Low oil level in crankcase
• High oil level in crankcase
• Contaminated eng ine oil
• Debris in engine oil
• Aerated engine oil
• Trapped air in the ICP system (particularly after an injector or high-pressure pump replacement)
• Intermittent IPR valve wiring connection. Inspect engine wiring harness connector and IPR valve
terminal for corrosion. Inspect terminal for bent or pushed back pins.
• Inoperative or stuck injection pressure regulator
• Leaks in ICP system
• Problem with ICP sensor or sensor circuit, incorrect sensor, system biased high or low
• Inoperative high-pressure hydraulic pump
Checks and Tests Comment
Check repair history – Determine if
trapped air caused by ICP system
disassembly.
If ICP system was serviced, vehicle should
be operated 20 miles
to validate system performance
Check o il level and quality. Check oil level, API classification. Inspect for debris. If
contamination is suspected, check oil filter element.
Check active and inactive DTCs. Repair any ICP sensor codes. See“ICP S ensor” (page 457).
Do ICP Operational Voltage Checks. Check KOEO pressure sensor value an
d voltage. See “ICP
Sensor” (page 457).
Do IPR Pin-Point Diagnostics.
Test will verify IPR circuit continuity. See “IPR” (page 494).
Do KOEO Standard Te st. Test will verify IPR circuit continuity. See “Performance
Diagnostics” – Section 6 (page 205).
Do KOER Standard Test. Test will verify majo r ICP sys
tem failure. See “Performance
Diagnostics” – Section 6 (pag
e 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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