P0691

Wiring Diagram:

Cooling Fan Relay Control Circuit 1 Low Voltage:

P0691 - COOLING FAN RELAY CONTROL CIRCUIT 1 LOW VOLTAGE
The ECM controls both cooling fan motors by controlling two drivers, which pull each cooling fan control circuit to ground. The combination of high/low inputs to the cooling fan control module allow Off. low, medium and high cooling fan speeds. When the ECM fan control driver is Off, the cooling fan control module input is high (battery voltage). When the ECM fan control driver is On, the cooling fan control module input is low (0 volts). When fan control 1 and 2 are commanded Off, neither cooling fan will run. When fan control 2 is On and fan control 1 is Off, both fans will run at low speed. When fan control 1 is On and fan control 2 is Off, both fans will run at medium speed. Finally, when fan control 1 and 2 are On, both fans will run at high speed. Both cooling fan motors will begin to run on low whenever the ECT is above 96°C (204°F), A/C is commanded On with a high side pressure above 1199 kPa (174 psi) gauge pressure or on high if a low/high fault exists in the ECT sensor circuit. DTC P0691 will set if the ECM detects lower than normal feedback voltage when fan control 1 is commanded Off with the engine cranking/running.

DTC PARAMETERS
DTC P0691 will set if fan control 1 feedback voltage is less than 2.6 volts when fan control 1 is commanded Off when:
^ Condition exists for longer than 0.5 seconds
^ Engine speed is greater than 40 rpm
^ Main relay voltage is between 7.5 and 15 volts

DTC P0691 diagnostic runs continuously once the above conditions have been met.

P0691 is a type B DTC.

DIAGNOSTIC AIDS
To locate an intermittent problem, use Scan tool to monitor DTC P0691 LAST TEST with engine running, ECT below 96°C (204°F) and A/C relay commanded Off. Wiggling wires while watching for a change from PASSED to FAILED may locate the area where a short to ground in the wiring may exist.