Chart C-12, 2.5L (1 Of 2), Cooling Fan CKT Diagnosis: Notes

Primary (No. 1) and secondary (No. 2) cooling fans are ECM controlled based on inputs from coolant temperature sensor, A/C control switches, vehicle speed and state of A/C compressor/engine cooling fan temperature switch. ECM controls cooling fans by grounding circuits No. 335 and/or No. 473, which energizes cooling fan relay(s). When cooling fans are energized, battery voltage is supplied to fan motors.

ECM grounds circuit No. 335 when coolant temperature is greater than 223°F (106°C) or when A/C has been requested. A/C compressor/engine cooling fan temperature switch opens with high A/C pressure, approximately 250 psi (17.6 kg/cm² ). ECM then grounds circuit No. 473 to energize secondary (No. 2) cooling fan relay. When ECM energizes either relay, ECM will keep fan relay on at least 60 seconds or until vehicle speed exceeds 70 MPH for fan No. 1 or 40 MPH for secondary(No. 2) fan. If Code 14 or 15 sets, ECM is in back-up mode: fan No. 1 will run at all times.

NOTE: Test numbers refer to test numbers on diagnostic charts.

With diagnostic terminal grounded, cooling fan control driver(s) will close, which should energize fan relay(s).
If A/C compressor/engine cooling fan temperature switch or circuit is open, both fans would run whenever A/C is requested.
When A/C compressor/engine cooling fan temperature switch opens, secondary (No. 2) cooling fan relay is energized by ECM. Switch opens when A/C line pressure exceeds approximately 250 psi (17.6 kg/cm² ).