Chart C-12, Cooling Fan Circuit Diagnosis: Notes

Powertrain Control Module (PCM) controls cooling fans based on various inputs. Battery voltage is supplied to primary and secondary fan relays on relay terminal "E". Ignition voltage is supplied to primary and secondary fan relays on relay terminal "D". Grounding circuit No. 335 (relay terminal "F") will energize primary cooling fan relay (fan No. 1) and supply battery voltage to primary cooling fan motor. Grounding circuit No. 473 (relay terminal "F") will energize secondary cooling fan relay (fan No. 2) and supply battery voltage to secondary cooling fan motor. When certain Diagnostic Trouble Codes (DTC) are set, PCM will enable cooling fans.

1. With output/field service enable terminal grounded at DLC, cooling fan control driver(s) will close, energizing fan control relays.
2. Cooling fans should come on anytime A/C system is operating.
3. Comparing Tech 1 scan tester A/C refrigerant pressure and manifold gauge set pressure will determine if A/C refrigerant pressure sensor is out of range. An out-of-range A/C refrigerant pressure sensor can cause cooling fans to operate at wrong times.