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Error P1491 Radiator Fan Control Relay
04-11-2008, 07:27 PM
Vehicle: 2003 Dodge Grand Caravan 3.3 Litre
I also have my CE light on. Hooked up my reader and got the "P1491 Radiator Fan Control Relay" code. I have checked my rad fan fuse and it is okay. My attempt to locate the rad fan relay took me from the rad fan wire to a device that looks like a heat sink. It is located on the vehicle frame between the rad. and front grill. Is this the rad fan relay? If it is I'm not sure how I would replace it. It seems rivited to the frame. Any help would be greatly appreciated.
04-13-2008, 02:13 PM
I looked up on alldata for my 2002, the picture looks like it is riveted to the frame, here below I cut and paste what it says.
The solid state radiator fan relay is controlled by the Powertrain Control Module (PCM) by way of a Pulse Width Modulated (PWM) signal. The relay control circuit supplies a 12 volt signal to the PCM. The PCM then pulses the ground circuit to achieve fan on time. The relay provides a voltage to the fan motors which is proportional to the pulse width it receives from the PCM. The duty cycle ranges from 30% for low speed operation, then ramps-up to 100% for high speed operation. This fan control system provides infinitely variable fan speeds, allowing for improved fan noise, A/C performance, better engine cooling, and additional vehicle power.
To control operation of the relay, the PCM looks at inputs from:
Engine coolant temperature
A/C pressure transducer
Ambient temperature from the body controller
Transmission oil temperatureThe PCM uses these inputs to determine when the fan should operate and at what speed
04-13-2008, 04:49 PM
Thanks for the info. I however am unsure of how to proceed to correct this situation. How does one replace the relay? I have a set of wires that lead to a plastic adapter and this all plugs into a heat sink that is riveted to the frame. I don't see how I can replace anything unless the relay is located somewhere else. Actually I am not sure that the relay is the problem, do you know what else I should be looking at in regards to this error code?
04-13-2008, 05:45 PM
The only way to be sure is to have a DRBIII to scan and test the circut, it is probably worth the $100.00 to have a scan done otherwise you could end up replacing parts that are not necessary,
I am not sure what the fan relay cost is but you can end up replacing and still spending the money at the dealer for a scan.
He's the instructions from my 02 for fan relay replacment.
Disconnect and isolate the battery negative cable.
Remove the radiator crossmember to front fascia closure panel.
Disconnect the relay electrical connector.
Remove the rivet attaching the relay to the front bumper beam.
Remove the relay.INSTALLATION
CAUTION: The relay mounting location is designed to dissipate heat. Ensure the relay is securely attached to prevent relay "thermal" shutdown and relay damage, resulting in possible engine overheating.
Position relay and install a new rivet.
Connect electrical connector to relay.
Install closure panel and attaching screws.
Connect negative cable to battery.
04-21-2008, 11:41 AM
I know your suggestion for a DRBIII scan would be the most efficient in precisely locating the problem but I decided to go to a local scrap yard and got a used relay for ten bucks. A new Mopar relay is 100 bucks. I replaced using your instructions and the CE light flashed 3-4 times then went off. It has been of now for nearly a week. I am only cautiously optimistic. Time will tell if the problem was only the relay or something else.Thanks for you good suggestions and help. What I didn't realize before was that the relay was located under the heat sink.
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