B6 A4 Cooling Fan Troubleshooting

[clewis]

I ran code today for an unrelated issue and noticed a (P1931 - 002 - Lower Limit Exceeded - Intermittent). I did a few tests and couldn't get the smaller fan to turn on.

I let the car warm at at idle and the larger fan turned on low speed when the temp hit 100C. I turned the AC on an the larger fan went into high speed. The smaller fan never turned on.

Does anyone have experience with this code or issue? I really don't want to throw $300 at a new control module unless I can troubleshoot it and know that's the cause. Maybe a relay or fuse somewhere? I'm happy to pull things apart to figure this out:)

Thanks in advance!!!

2004 A4 Quattro Ultrasport, 6 Speed, GIAC Stage 1+, DSMIC, S4 Brakes

[Mike@PureMS]

The hard thing with working with the fans is that they're hard connected to the fan control module. There isn't a connector you can easily disconnect to test them. Plus there isn't much room there to even work on them. But you should cut the wires to the smaller fan, then simply apply 12V to the fan and see if it'll turn on. If it doesn't you've got a bad fan.

If the fan does turn on normally, then chances are you may have a bad fan control module.

[diagnosticator]

The left side large fan is the radiator fan, and the right side fan is the A/C condenser fan. The condenser fan is controlled by the A/C control module in the dash. The larger radiator fan is controlled by the engine ECU. Both fans receive power from the fan power control module. The PCM for the fans converts Pulse width modulated control signals into PWM power supplied to the fan motors. The fan motors can fail also.