What does it mean?
This code applies to vehicles with a water-to-air charge air cooler, where an electric pump circulates coolant through a separate low temperature loop to take heat out of the compressed intake air. The module commands the pump and then checks whether the expected cooling actually happens, using the intake air temperatures across the cooler and, on many systems, feedback about pump speed or current draw. When the pump runs but the cooling effect or the feedback does not match the command, this performance code is stored. It differs from a plain circuit fault because the electrical connection is present; the problem is flow, not wiring. Since hot charge air costs power and raises the risk of knock, the module usually limits boost while the fault is active.
Symptoms
- Intake air temperature staying high under sustained load, visible in live data
- Power reduction and boost limiting, most noticeable when towing, climbing or in hot weather
- No pump noise from the front of the vehicle when the key is turned on or after a hot shutdown
- MIL on, sometimes with charge air cooler efficiency codes
- Knock retard on petrol engines and more smoke on diesels
Likely causes
- Air trapped in the low temperature coolant circuit after a repair or a slow leak, so the pump cannot move coolant properly
- Low coolant level in the separate low temperature reservoir
- Worn, seized or internally failing pump that spins but produces little flow
- Blocked low temperature radiator, restricted hoses or a stuck check valve
- Degraded or wrong coolant that has lost its heat transfer properties, or deposits inside the cooler
- Weak supply voltage to the pump from a corroded connector, a tired relay or a poor ground
- Pump control module fault where the pump is driven electronically
- Intake air temperature sensor error that makes correct cooling look insufficient
How to fix it
- Command the pump on with a bidirectional scan tool and listen and feel for flow at the hoses
- Check the low temperature circuit level and top it up, then bleed the loop exactly as specified; trapped air is a very common cause
- Measure voltage at the pump connector while it is running and check the ground with a voltage drop test
- Log intake air temperature before and after the cooler against ambient during a load drive to quantify the cooling loss
- Inspect the low temperature radiator for external debris and internal restriction, and squeeze the hoses to find a collapsed section
- Verify that any auxiliary fan for that radiator operates
- Replace the pump when it is proven to produce no flow with good supply voltage, then bleed the system and repeat the load test