What it means
CAC coolant pump A control voltage below expected range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The charge air cooler coolant pump A circulates coolant to cool compressed intake air, and the control module monitors its control-circuit voltage. P023B sets when that voltage is below the expected range, often because the wire is shorted to ground or a corroded connection adds resistance.
Common causes
Most likely first.
- Wiring shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check-engine light on
- Reduced engine power or acceleration
- Poor turbo response
- Reduced fuel economy
How to diagnose it
- Record freeze-frame data and check scan-tool data for pump A command or status when the low-voltage fault occurs.
- Inspect pump A’s connector and harness for chafed insulation, moisture, corrosion, loose pins, or wiring contacting a grounded surface.
- Check the pump A control circuit for a short to ground and inspect its terminals for corrosion or high resistance.
- With the circuit safely isolated, test continuity and check the relevant power, ground, and control paths against the wiring diagram and manufacturer’s specification.
- If the wiring and connections pass, test pump A and the module’s control output using the manufacturer’s diagnostic procedure.
Common fixes
- Clean and secure corroded or loose pump A connector terminals.
- Repair chafed wiring that shorts the control circuit to ground.
- Replace a damaged connector or harness section causing high resistance.
- Replace pump A or repair the module output only if testing confirms that component is faulty.
Can I keep driving?
If power or turbo response is reduced, avoid hard acceleration and towing because the charge air cooler may not be receiving adequate coolant flow. Stop if the engine overheats or loses enough power to make driving unsafe.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.