P1491- Cooling Fan Won’t Turn On—Chrysler Minivan
Many owners report overheating in their minivans because the electric cooling fan will not come on. This may be accompanied by trouble code P1491—Radiator Fan Control Relay Circuit Malfunction.
Start your diagnosis at the fan relay module which is located below the battery box on the left frame rail. The Grey wire is hot at all times and fused by fuse #24 in the power distribution center. The Black wire is the ground. The Light Green/Dark Blue wire goes to the Powertrain Control Module which provides ground to the fan relay when cooling fan operation is needed. The Dark Green wire provides switched power to the fan motors.
Using a digital test meter, check for 12 volts on the Grey wire. Check for good ground at the Black wire. If you have good results with those two tests, ground the Light Green/Dark Blue wire at the relay. The fans should start up and run at high speed. Now is a good time to check the current draw on the fans—they should not draw more than 15 amps. If the fans do not run, check the operation of the fan motors by jumpering the Grey wire to the Dark Green wire. If the fans work, the relay is bad.
When replacing the relay, always clean the mounting surface and apply new thermo grease.
To check operation of the PCM, disconnect the connector to the engine coolant temperature sensor and check the Light Green/Dark Blue wire to see if the PCM is switching the ground to the relay. If it does not, check that wire at the PCM connector. If it switches there, you have an open between the PCM and the relay.
Common problems with this vehicle: Poor ground at for the relay, bad relay, bad ground for the engine coolant temp sensor.
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© 2007 Rick Muscoplat
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