P023B
PowertrainCharge Air Cooler Coolant Pump Control Circuit Low
Usually a smaller job than the scary name suggests. The ECU has seen the voltage on the circuit that drives your charge air cooler coolant pump drop too low, which points at the wiring, a connector, a fuse, or the pump itself rather than anything deep inside the engine. This is the little auxiliary electric pump that pushes coolant through the intercooler on turbo and supercharged petrols with a water-to-air setup, and most of the time you're chasing an electrical fault, not buying a whole cooling system.
ⓘ Information only. This page provides general educational information about fault code P023B. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P023B mean?
P023B is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Charge Air Cooler Coolant Pump Control Circuit Low.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on, frequently the only thing you'll notice day to day
- • Acceleration goes flat under boost when the intake charge can't be cooled properly
- • Intake air temperatures climbing higher than normal during hard pulls or towing
- • A drop in fuel economy that creeps in over time
- • On some cars, a brief loss of power or soft limp mode when you put your foot down
Possible causes
Causes commonly associated with P023B, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. The auxiliary coolant pump itself has failed electrically or seized internally, common once these little pumps get age and miles on them
- 2. Chafed, corroded or broken wiring in the pump control circuit, often where the loom runs near heat or vibration
- 3. A dirty or loose connector at the pump or at the ECM giving a poor electrical contact
- 4. A blown fuse or tired relay on the pump's power feed
- 5. An air lock in the intercooler coolant circuit after recent work, which can confuse the pump and the control side
- 6. A failed ECM, which is the last thing to suspect after everything else checks out clean
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Back-probe the pump connector and check for proper supply voltage and a good ground with the ignition on, since a missing feed or bad earth explains a low-voltage code straight away
- 2. Inspect the wiring and connector at the pump for corrosion, melting, green crust or pins that have backed out, and wiggle-test the loom while watching live data
- 3. Check the fuse and relay that feed the pump before condemning anything expensive
- 4. Bench-test the pump on a 12-volt supply to confirm it actually spins and moves fluid; a dead pump tells you the answer
- 5. Confirm coolant level and condition in the intercooler circuit and bleed out any trapped air if work has recently been done there
- 6. Pull any companion codes and check for a manufacturer service bulletin on your model before throwing parts at it
Common questions about P023B
Will my car fail the MOT with a P023B stored? +
The code on its own won't fail you, but if the engine warning light is lit when you drive onto the ramp, the tester has to mark it and that can mean a fail under the emissions and warning lamp rules. Sort the underlying fault, clear the light, and run the car for a few drive cycles so the lamp stays off before the test. A pump that's properly dead and a light that keeps coming back will count against you.
What am I looking at to fix this, ballpark? +
If it turns out to be a connector clean-up, a fuse, or a small wiring repair, an independent garage might sort it in the low two-figure to low three-figure range once diagnostic time is added. A replacement auxiliary coolant pump tends to land in the low to mid three-figure band fitted, depending on how buried the pump is. A main dealer will push the top end of that for the same job. Get the diagnosis nailed first so you're paying for the right repair.
How do I tell whether it's the pump or just the wiring on my car? +
Go to the pump connector first. Switch the ignition on and check you've got supply voltage and a solid ground at the plug. If the feed is missing or weak, your fault is upstream in the wiring, fuse or relay, and the pump may be fine. If the supply is good but the pump still won't run when you put 12 volts straight across it on the bench, the pump is your problem. That one test splits the cheap fix from the expensive one in about ten minutes.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →