PACCAR MX (2004 Emissions) Fault Code: P00B7 Coolant Pump Speed – Data Valid but Too Low When High Speed is Requested

PACCAR MX (2004 Emissions) Fault Code: P00B7 Coolant Pump Speed – Data Valid but Too Low When High Speed is Requested

SET CONDITIONS:
The PCI ECU (D420) detects that the average coolant pump speed is 400 rpm lower than expected.

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

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?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Prolonged engine starting (>12 seconds)
2. Malfunctioning coolant pump speed sensor or wiring
3. Malfunctioning two-stage coolant pump 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 the signal of the coolant pump speed cannot be read by the PCI ECU, the signal coolant pump speed (actual) in the diagnostic service tool is 333 rpm (default value).