Hard Or Intermittent Trouble Code F41: Notes

Code is set by BCM if it receives improper cooling fans feedback voltage. Cooling fans control module is designed to change feedback voltage on circuit No. 791 as follows:

• 12 volts if fans have been turned off.
• 0 volt if fans have been turned on.
• 12 volts if fans have been turned on and an excessive current draw exists (stalled or shorted fan motors).
• 0 volt if both fan connectors are open.

The BCM will set code if either of the following conditions exist:

1. A) The BCM has commanded fans off, but feedback voltage remains low. The BCM will keep code stored hard for rest of ignition cycle and continue providing a normal control signal to cooling fans control module. The BCM will again test this condition during next ignition cycle to determine if malfunction has become intermittent.
2. B) The BCM has commanded fans on, but feedback voltage remains high. The BCM will command fans off to protect the system from possible stalled or shorted motor condition. If control temperatures (coolant and A/C high side) should drop below turn off points and later require the fans on, the BCM will repeat test to determine if malfunction has become intermittent.

Both of the above conditions will result in illumination of "COOLANT TEMP/FAN" light whenever control temperatures require cooling fans operation.

1. The cooling fans override feature (parameter "F.8.5") can be used to evaluate system operation. If either fan is off when "high fans" are commanded or if either fan is on when "fans off" is commanded, appropriate diagnostic path can be followed to isolate malfunction.
2. The cooling fans status light ("AUTO FAN") can be used to evaluate feedback signal being received by BCM. If light does not agree with actual fans operation, circuit No. 791 must be investigated for possible malfunction. If light does agree with commanded fans operation within appropriate time period, then cause of code is not currently present.