P023A - Charge Air Cooler Coolant Pump Control Circuit/Open
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P023A is a diagnostic trouble code (DTC) for an 'Open Circuit' in the Charge Air Cooler (CAC) Coolant Pump control circuit. On modern turbocharged or supercharged engines with liquid-to-air intercooling, an electric water pump circulates coolant through the CAC heat exchanger. The Engine Control Module (ECM) monitors the continuity of this circuit. If the ECM command signal does not result in the expected current flow or voltage drop, P023A is triggered. This fault inhibits intake charge cooling, leading to increased IAT (Intake Air Temperature) and subsequent derating of engine power to protect components.
Possible Causes
Defective electric coolant pump (internal open circuit in windings)
Loose connection or oxidized terminal in the pump connector
Wiring harness break between the ECM and the pump
Faulty coolant pump relay (on systems using relay control)
Internal ECM hardware failure
Symptoms
Recommended Solution
- Visual Inspection: Check the pump connector for signs of water ingress, corrosion, or backed-out pins.
- Fuse Check: Inspect all fuses related to the auxiliary cooling system.
- Voltage Drop Test: Check for 12V supply and solid ground at the pump connector while the system is commanded ON.
- Signal Testing: Use an oscilloscope to verify the PWM (Pulse Width Modulation) signal from the ECM.
- Component Test: Measure resistance (Ohm) across the pump terminals. An infinite reading indicates an internal open circuit.
- Action: Replace the electric coolant pump or repair the wiring harness. Clear DTCs and perform a test drive while monitoring IAT values.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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