PACCAR MX (2004 Emissions) Fault Code: P3101 Coolant Pump Speed – Data Valid but Too Low, When Low Speed is Requested

PACCAR MX (2004 Emissions) Fault Code: P3101 Coolant Pump Speed – Data Valid but Too Low, When Low Speed is Requested

SET CONDITIONS:
The PCI ECU (D420) detects that the average coolant pump speed is 400 rpm lower than expected for more than 5 seconds when the pump is controlled to run at low speed.

DIAGNOSTIC CONDITION:
This diagnostic runs continuously when the engine is running and the coolant pump is activated to run at low speed.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC will change to inactive after the ignition is keyed off and on again and the diagnostic runs and passes. To validate the repair, monitor the coolant pump with the diagnostic service tool when the engine is running.

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?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Slipping poly-V-belt
2. Malfunctioning two-stage coolant pump
3. Malfunctioning coolant pump speed sensor or wiring

ADDITIONAL INFORMATION:
1. The coolant pump speed is measured by the coolant pump speed sensor (F805).

IMPORTANT: The PCI ECU is not able to detect a short circuit or an open circuit of the coolant pump speed sensor or its wiring. It can only detect if the expected coolant pump speed is reached. If no signal is received from the coolant pump speed sensor, the coolant pump speed (actual) in the diagnostic service tool displays 333 rpm when the engine is running.

2. When the engine is running, the minimum coolant pump speed (actual) which can be displayed in the diagnostic service tool is 333 rpm.

3. The two-stage coolant pump (L142) is controlled by the PCI ECU (D420).

IMPORTANT: The PCI ECU is not able to detect a short circuit or an open circuit of the coolant pump solenoid or its wiring. It can only detect if the expected coolant pump speed is reached.

4. Depending on the cooling request by the engine or vehicle (for example cabin heater), the PCI ECU activates the solenoid of the coolant pump to drive the impeller at low or high speed:
– Solenoid activated, the pump runs at high speed
– Solenoid not activated, the pump runs at low speed

5. If this DTC becomes active the pump is forced to run at the high speed.

6. The driver is not informed by a warning when this DTC is active.