P023B — Charge Air Cooler Coolant Pump Control Circuit Low

P023B — Charge Air Cooler Coolant Pump Control Circuit Low. A fault in the engine cooling and temperature control. Short, gentle driving to a shop is usually possible. Typical causes: water pump or radiator issues, failed cooling fan or fan relay, wiring faults in the sensor circuit.

powertrain (engine/transmission)

Is it safe to drive?

Repair promptly and avoid hard driving P023B indicates a low reading from the charge-air cooler coolant pump control circuit. Reduced charge-air cooling is possible, so avoid sustained high-load or boosted driving until the circuit and pump are tested. Stop safely if charge-air temperature rises unexpectedly or the vehicle enters a protection mode.

Typical symptoms

  • The check-engine light may illuminate with P023B stored in the powertrain controller.
  • The charge-air cooler coolant pump may remain off, run intermittently, or cycle when it should be operating continuously.
  • Charge-air temperature may rise higher than expected under acceleration or boost, particularly when the pump is not circulating coolant.
  • Some vehicles may enter a temperature or boost-protection strategy and restrict engine output.
  • There may be no visible symptom beyond the stored P023B, especially if the pump failure is intermittent.

Common causes

  • Open or high-resistance wiring in the charge-air cooler coolant pump power or ground circuit can make the voltage fall below the P023B threshold.
  • A short to ground or low-reference fault in the pump control circuit can set P023B even when the pump motor is still functional.
  • Corroded terminals, a loose connector, heat-damaged insulation, or coolant intrusion can create an intermittent low-voltage condition.
  • A failed charge-air cooler coolant pump motor or internal pump drive can leave the control circuit reading abnormally low.
  • A defective powertrain control module driver or poor control-circuit ground can cause the PCM to detect P023B.

How to diagnose with an OBD scanner

  1. Confirm P023B and capture operating data Connect an ELM327 or AIScanAuto scanner, read stored and pending codes, and save the freeze-frame data. Determine whether P023B appears at startup, during idling, or under load; do not clear it before recording the conditions.
  2. Inspect the pump and coolant circuit With the engine cool, check the coolant reservoir, pump area, hoses, and charge-air cooler lines for leaks or damage. Inspect the pump connector and nearby wiring for corrosion, heat chafing, pin damage, or coolant contamination.
  3. Test the pump connector and harness Use the vehicle wiring diagram to identify the pump supply, ground, and control terminals. Check connector tension and terminal resistance, then perform a wiggle test while monitoring the circuit for changes that correspond with P023B.
  4. Measure control voltage and ground Back-probe the pump circuit with the engine running or as specified by the manufacturer. A high PCM command with a low voltage at the pump indicates an open, shorted, or high-resistance circuit; correct command and ground readings with no pump operation point toward the pump.
  5. Isolate the pump from the wiring Following the manufacturer procedure, disconnect the pump and measure supply, ground, and control-circuit values at the connector. Verify pump current draw and operation before condemning it. A generic ELM327 or AIScanAuto tool may not be able to command this pump directly.
  6. Verify the repair After repairing wiring, terminals, coolant levels, or replacing the pump, clear P023B with the scanner. Repeat the original operating conditions and confirm stable pump operation, normal charge-air temperature, and no return of the low-circuit code.

Approximate repair cost

A typical independent-shop range is $250-$1,500 USD for diagnosis plus wiring, connector, or charge-air cooler coolant pump repair. Figures are estimates and vary by region and vehicle.

Common questions

What does P023B specifically indicate?

P023B means the controller detected voltage below the expected threshold in the charge-air cooler coolant pump control circuit. It identifies an electrical low condition, not necessarily a failed pump.

Does P023B prove the coolant pump has failed?

No. P023B can result from damaged wiring, a short to ground, a poor connector, an inadequate ground, or a PCM-side fault, so voltage and current tests should precede pump replacement.

Can the vehicle be driven with P023B?

Driving cautiously may be possible if there are no temperature warnings or performance faults, but sustained high-load driving should be avoided because loss of charge-air cooling can contribute to excessive charge temperatures.

Can an ELM327 or AIScanAuto scanner diagnose P023B?

Yes. An ELM327 or AIScanAuto scanner can confirm P023B, display freeze-frame information, and clear the code, but it may not command or test the charge-air cooler pump directly. Electrical measurements are still required.

When your OBD2 scanner displays P023B, the engine control module has identified a problem with the electrical circuit that manages the charge air cooler coolant pump. The official definition reads "Charge Air Cooler Coolant Pump Control Circuit Low." This falls under the powertrain category, meaning it affects engine or transmission operation.

"Circuit low" indicates the voltage in the pump control circuit has dropped below the acceptable threshold, hovering near ground potential. This typically stems from a short to ground somewhere in the wiring, a broken or chafed wire making contact with metal, a missing power supply, or a faulty component pulling the signal down. The control module watches this circuit constantly during operation. Once voltage readings stay outside the normal range for a predetermined number of drive cycles, the module stores P023B and illuminates the check engine light. The freeze frame data captured alongside the code shows exactly what the engine was doing at the moment of failure — engine speed, load, temperatures, and vehicle speed — giving you a solid starting point for diagnosis.

Many turbocharged engines use a liquid-cooled charge air cooler (also called an intercooler) to drop the temperature of compressed air before it enters the cylinders. This system needs its own dedicated coolant pump, controlled by the ECM through a dedicated circuit. When that control circuit fails to maintain proper voltage, the result is P023B.

Symptoms of P023B

When P023B is active, you may notice one or more of the following:

  • Weak or nonexistent cabin heating
  • Cooling fans running at high speed continuously
  • Temperature gauge reading lower than normal or failing to reach operating temperature
  • Overheating warnings in more serious cases
  • Check Engine Light illuminated
  • Noticeably higher fuel consumption due to the engine running outside optimal temperature

Common Causes of P023B

The most frequent culprits behind P023B include:

  • Failed charge air cooler coolant pump dragging the circuit voltage down
  • Signal wire shorted to ground from damaged or chafed insulation
  • Missing 12V supply voltage to the pump circuit (blown fuse, bad relay)
  • Low coolant level or trapped air in the charge air cooler coolant circuit
  • Faulty coolant temperature sensor causing incorrect pump command signals
  • Thermostat stuck in the open position
  • Cooling fan relay or fan motor issues indirectly affecting the circuit

How to Diagnose P023B

Follow these practical steps to pinpoint the cause of P023B:

  1. Connect your OBD2 scanner and confirm P023B is stored. Save the freeze frame data — it tells you engine speed, load, temperature, and speed at the moment the fault triggered.

  2. Look for any related diagnostic trouble codes. Codes in the same system often point to the root cause. Check manufacturer TSBs for your specific make and model — many issues have known factory fixes or software updates.

  3. Visually inspect the wiring harness and connectors for the charge air cooler pump. Look for chafed wires, broken insulation, corrosion at the terminals, or loose connections.

  4. Test the circuit with a multimeter. Check for 12V power at the pump connector first. Then measure resistance from the signal wire to ground — near-zero ohms confirms a short to ground in the harness.

  5. Verify coolant level and thermostat operation. Feel the upper and lower radiator hoses during warm-up to confirm the thermostat opens at the correct temperature.

  6. Clear the code, complete a full drive cycle matching the conditions from the freeze frame, and verify P023B does not return.

Repair Options and Costs for P023B

Charge air cooler coolant pump replacement — If the pump itself is faulty, expect to pay $250–$700 total (parts: $150–$400, labor: $100–$300).

Wiring harness repair — Repairing damaged wiring typically runs $100–$400 depending on the extent of the damage and labor involved.

Coolant temperature sensor replacement — One of the simpler fixes. Parts cost $30–$80, with labor adding $50–$100, for a total of $80–$180.

Cooling system flush and coolant top-off — If low coolant or air pockets caused the issue, a full flush and refill runs $100–$200.

Thermostat replacement — Parts range from $80–$200, with labor around $100–$150, totaling $180–$350.

Cooling fan relay or motor replacement — Can run $150–$500 depending on the component and vehicle.

The total cost to fix P023B typically falls between $100 and $700, though more complex repairs involving multiple components can reach $1,000–$1,200. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can You Drive with P023B?

P023B warrants caution. The vehicle may still run, but the underlying cooling issue means the engine is not regulating temperature properly. Monitor the temperature gauge closely while driving. A thermostat stuck open mainly hurts fuel economy, but any sign of overheating demands an immediate stop — continuing to drive an overheating engine risks head gasket failure, warped cylinder heads, and other costly damage.

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