PACCAR MX (2004 Emissions) Fault Code: P009F Common Rail Pressure Release Valve – Malfunction Detected During Check

PACCAR MX (2004 Emissions) Fault Code: P009F Common Rail Pressure Release Valve – Malfunction Detected During Check

SET CONDITIONS:
The PCI ECU (D420) detects that the common rail pressure release valve is stuck for more than 3 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. Engine load is steady and;
2. Engine speed is between 1000 and 1700 rpm and;
3. When the rail pressure operating state is: Pump unit only
4. Requested rail pressure is more than 700 bar [10,153 PSI] and;
5. Difference between the actual and requested rail pressure is less than 20 bar [290 PSI] and
6. Engine running time since the last completed test is more than 4 hours

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Common rail pressure release valve failure

ADDITIONAL INFORMATION:
1. One of the functions of the common rail pressure release valve (L094) is to rapidly decrease the rail pressure (dumping) in certain engine operations. During normal operation the valve is electronically controlled (duty cycle) to keep it closed.

2. For this diagnostic, the common rail pressure release valve is checked via an autonomous test to see whether it’s stuck. During steady state engine operating conditions, the PCI ECU momentarily decreases the common rail pressure release valve current. This should result in fuel being dumped from the rail causing a pressure drop. Since the rail pressure is close-loop controlled, the PCI ECU activates the pump units for longer to maintain the requested rail pressure. If the common rail pressure release valve is stuck, the rail pressure remains the same when the control current of the valve is decreased.

3. When this DTC is active:
– The engine torque is reduced.
– The engine runs in protection mode.
– The maximum rail pressure is limited to 1300 bar.