What causes fault code P023B?

• Most likely: Short circuit to ground in the coolant pump wiring harness • Likely: Faulty electric coolant pump (internal short) • Possible: Connector corrosion or poor terminal tension • Rare: Faulty Engine Control Unit (ECU) or driver module failure

How do you fix fault code P023B?

STEP 1: Visually inspect the connector at the charge air cooler pump for moisture, corrosion, or backed-out pins. STEP 2: Check the fuse dedicated to the intercooler pump. STEP 3: Using a multimeter, check for battery voltage (12V+) at the pump power terminal with the ignition on. STEP 4: Measure resistance across the pump terminals; a value near 0 Ohms indicates an internal short. STEP 5: Conduct a continuity test on the control wire back to the ECU to ensure it is not shorted to ground against the chassis. STEP 6: If wiring and power are verified, replace the electric coolant pump.

Powertrain (Engine & Gearbox)Standard EOBD

P023B - Charge Air Cooler Coolant Pump Control Circuit Low

Q: What are the symptoms of fault code P023B?

• Check engine light (MIL) illuminated • Reduced engine performance (Limp mode potential) • Increased Intake Air Temperatures (IAT) • Poor acceleration due to ECU limiting boost pressure to protect the engine

Last updated:1 February 2026

Related:Intercooler, Electric Coolant Pump, Engine Control Unit (ECU), IAT-sensor (Intake Air Temperature)

System

Powertrain (Engine & Gearbox)

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Technical Description

P023B is a generic OBD-II diagnostic trouble code indicating that the Engine Control Unit (ECU) has detected an abnormally low voltage in the control circuit for the Charge Air Cooler (CAC) water pump. In modern forced-induction engines, dedicated liquid-to-air intercooling systems utilize an electric pump controlled by the ECU, often via PWM (Pulse Width Modulation). This code triggers when the ECU identifies that the circuit voltage is lower than the commanded or reference value, typically signifying a short circuit to ground or a failure within the pump's internal electronics.

Possible Causes

Short circuit to ground in the coolant pump wiring harness

Faulty electric coolant pump (internal short)

Connector corrosion or poor terminal tension

Faulty Engine Control Unit (ECU) or driver module failure

Symptoms

Check engine light (MIL) illuminated

Reduced engine performance (Limp mode potential)

Increased Intake Air Temperatures (IAT)

Poor acceleration due to ECU limiting boost pressure to protect the engine

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P023B - Charge Air Cooler Coolant Pump Control Circuit Low

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P023B - Charge Air Cooler Coolant Pump Control Circuit Low

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