Circuit Description

PCM controls cooling high speed operation through the use of a high fan relay and a control circuit. If PCM commands fan high speed operation and senses fan did not turn on, or commands fan operation off and fan continues to run, DTC P0481 will be set.

Conditions required for setting DTC are:

• Ignition voltage is greater than 10 volts.
• Engine run time is greater than 32 seconds.

  Both previously listed conditions are met, and one of the following conditions are met for 25 seconds within a 50 second period:

• PCM senses voltage is high with high speed fan off for 25 seconds within a 50-second period.
• PCM senses voltage is low with high speed fan on for 25 seconds within a 50-second period.