What does it mean?
This code is stored when the module reads a higher voltage on the charge air cooler cooling fan control circuit than the commanded state permits. With the driver commanded on the line should be pulled down toward ground; if it stays up near battery voltage the current is not flowing, which points either to an open circuit somewhere between the module and the fan, or to voltage being fed into the line from another source. Because both look identical to the module, the code covers open circuits and shorts to a supply together. The practical consequence is the same in either case: the fan does not run, so the charge air cooler loses its low speed cooling and the engine ends up ingesting hot air in traffic.
Symptoms
- Fan never runs, even in hot conditions or after a hot shutdown
- Intake air temperature staying high at low vehicle speed
- Reduced power and boost limiting when the cooler cannot do its job
- MIL on with the fault present from key-on in many cases
- No change in fan behaviour when the module commands it with a scan tool
Likely causes
- Open circuit in the control wire, including a conductor broken inside undamaged insulation
- Fan connector not fully latched or a terminal pushed back after a repair
- Internally open fan motor or a failed fan control module presenting no load
- Control wire shorted to battery voltage against another circuit in a damaged harness
- Corroded terminals adding enough resistance that the circuit no longer pulls down
- Blown fuse upstream of the fan, so no current can flow through the control path
- Faulty output driver inside the control module, only after the wiring is proven
How to fix it
- Command the fan while measuring the control circuit voltage right at the fan connector
- Check the connector is fully seated and inspect for pushed-back and corroded terminals
- Test the control wire for continuity from the module to the fan and for a short to battery voltage
- Measure the fan motor resistance to see whether it is internally open
- Check the fuse and the supply side of the circuit, since a missing feed prevents any current flow
- Perform a voltage drop test on the fan ground while the circuit is commanded on
- Repair the open circuit or the short, or replace the fan when it is proven open, then confirm the circuit switches correctly on command