Cooling Fan Inoperative
1. Check power supply to the Integrated Relay Control Module (IRCM).^ Key off. Disconnect IRCM.
^ Measure voltage between pins 3 and 4 at the IRCM vehicle harness connector and battery negative post.
^ Is each voltage greater than 10.5 volts?
YES -- Go to step 2.
NO -- Service open in battery power circuit, and retest system.
2. Check fan motor operation.
^ Key off. IRCM disconnected.
^ Measure voltage between pins 3 and 4 at the IRCM vehicle harness connector and battery negative post.
^ Does the fan run?
YES -- Go to step 2a.
NO -- Go to step 3.
2a. Check fan motor operation.
^ Key off. IRCM disconnected.
^ Jumper pin 3 to pin 2 at the IRCM vehicle harness connector.
^ Does the fan run?
YES -- Go to step 6.
NO -- Go to step 5.
3. Measure battery voltage supply at fan (bypassing IRCM).
^ Key off. Disconnect cooling fan connector.
^ With the IRCM disconnected, jumper pin 3 to 6 at the IRCM vehicle harness connector.
^ Measure voltage at cooling fan vehicle harness connector between power and ground pins.
^ Is voltage greater than 8.0 volts?
YES -- Replace the fan motor, reconnect the IRCM and retest.
NO -- Go to step 4.
4. Verify cooling fan ground.
^ Key off.
^ With the cooling fan and IRCM disconnected, jumper pin 3 to pin 6 at the IRCM vehicle harness connector.
^ Measure voltage between voltage positive at the cooling fan vehicle harness connector and battery negative post.
^ Is the voltage greater than 8.0 volts?
YES -- Service open in the ground circuit to the fan. Reconnect all components and retest.
NO -- Service open in the power-to-fan circuit from the IRCM vehicle harness connector to the cooling fan vehicle harness connector. Reconnect all components and retest.
5. Measure battery voltage supply at the cooling fan, bypassing the IRCM
^ Key off.
^ With the cooling fan and the IRCM disconnected jumper pin 3 to pin 2 at IRCM vehicle harness connector.
^ Measure voltage at cooling fan vehicle harness connector.
^ Is the voltage greater than 8.0 volts?
YES -- Replace the fan motor. Reconnect the IRCM and retest.
NO -- Service open in the power-to-fan circuit from pin 1 and pin 2 of IRCM vehicle harness connector to the cooling fan vehicle harness connector. Reconnect all components and retest.
6. Check fan running mode (low).
^ Key off. Disconnect processor.
^ Reconnect IRCM. Key on, engine off.
^ Does the fan run?
YES -- Go to step 6a.
NO -- Replace the IRCM. Reconnect and retest.
6a. Jumper the High Electric-Drive (HEDF) signal to ground.
^ Key off.
^ With the key off, inspect processor 60 pin connector for damaged or pushed out pins, corrosion and loose wires. Service as necessary.
^ Install breakout box, leave processor disconnected.
^ With the key on, engine off, and the IRCM connected jumper test pin 52 to test pin 40 at the breakout box.
^ Does the fan speed change from low to high?
YES -- Go to step 7.
NO -- Replace the IRCM. Remove the breakout box, reconnect the processor and retest.
7. Check Engine Coolant Temperature (ECT) sensor.
^ Check engine coolant level.
^ Key off.
^ Install breakout box, with processor connected.
^ Warm engine to operating temperature before taking ECT resistance measurement.
^ Key off. Disconnect ECT sensor and measure the resistance of the sensor.
^ Is the resistance between 1500 ohms and 2000 ohms?
YES -- Replace processor, and retest.
NO -- Replace the ECT sensor, and retest.