Question about 1999 Jeep Grand Cherokee

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I have a 99 G Cherokee 4.0L with code P1491. I changed the sencor on the water neck and the fan relay too. The fan still won't come on. I tested the fan with live power and it come's right on. Any help or thought's whould be great. Thank you very much.

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Posted on Jan 02, 2017

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SOURCE: would not shift in to drive or reverse then lights interior flash

According to the fault code, there is no signal from the vehicle speed sensor to the OBD computer. A P1491 code is the radiator fan control circuit. I sounds like you may have an electrical problem that is causing a bunch of false readings. Have the computer reset and try again. You can get all of the fault codes at http://www.wjjeeps.com/faultcodes.htm#0500 Don't forget top rate this solution!!!

Posted on Mar 13, 2009

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SOURCE: How do I test the elec. motor and the fan relay on

with an ohm meter check if the wires going to the relay have power when they should. next use a jumper wire from the pos. battery terminal to the power connector on the fan if the fan starts to run off the jumper then its probably the relay to blame. hope this helps.

Posted on Dec 22, 2010

ZJLimited
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SOURCE: Where is the relay located for the code P1491? On a 2000 jeep grand Cherokee?

Hi there:
DTC P1491 - RAD FAN CONTROL RELAY CIRCUIT

DTC P1491 is for the cooling fan relay control circuit as you've found already. Start by checking the fuse for the fan relay. Its in the box under the hood, a 40 amp fuse.

If you've got a couple jumper wires, you can unplug the fan connector and carefully jump the fan to see if it works. The fan connector is on the right side of the back of the fan shroud. Unplug it and jump the black wire to ground and the green to positive. You've got to be very careful doing this though-you are in very tight quarters, its not hard for your jumper wires to touch each other in the connector and short together, and if you use small diameter jumper wires they will get hot quickly when the fan comes on.

If the fan doesn't come on when you jump it, or if it runs slow or sounds bad, you've got a bad motor and will need to replace the fan assembly. One thing that does happen somewhat often, is a bad fan motor will burn up the relay. If the fan motor is drawing too much current it will overload the relay and burn it up. This is why its so important that if the fan motor runs slow or makes noise that you replace it, or you may end up burning up relays frequently.

If the fan runs and the fuse is good, its very likely you just need a fan relay. This is a pulse width modulated relay, not the on/off clicker type you'd find in the fuse box. This unit is capable of infinite speed control. It gets very hot in operation, so its mounted to the body sheet metal to allow heat to dissipate through the sheet metal. The relay is mounted under the right headlamp held down with two 8mm screws. To get to it you have to remove the front bumper cover and headlamp bracketry to access the relay. These relays are pretty common.

Check and test this possible causes:
radiator fan ctrl rly circuit wire harn intermittent defect
radiator fan ctrl rly circuit wire harn observable defect
radiator fan relay ground circuit open
rad fan relay control circuit open
radiator fan relay control circuit short to ground
rad fan control relay defective
PCM defective

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Posted on Dec 20, 2011

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99 durango getting code P1491


code P1491 radiator fan control relay circuit.

Aug 11, 2013 | 1999 Dodge Durango

2 Answers

Where is the relay located for the code P1491? On a 2000 jeep grand Cherokee?


Hi there:
DTC P1491 - RAD FAN CONTROL RELAY CIRCUIT

DTC P1491 is for the cooling fan relay control circuit as you've found already. Start by checking the fuse for the fan relay. Its in the box under the hood, a 40 amp fuse.

If you've got a couple jumper wires, you can unplug the fan connector and carefully jump the fan to see if it works. The fan connector is on the right side of the back of the fan shroud. Unplug it and jump the black wire to ground and the green to positive. You've got to be very careful doing this though-you are in very tight quarters, its not hard for your jumper wires to touch each other in the connector and short together, and if you use small diameter jumper wires they will get hot quickly when the fan comes on.

If the fan doesn't come on when you jump it, or if it runs slow or sounds bad, you've got a bad motor and will need to replace the fan assembly. One thing that does happen somewhat often, is a bad fan motor will burn up the relay. If the fan motor is drawing too much current it will overload the relay and burn it up. This is why its so important that if the fan motor runs slow or makes noise that you replace it, or you may end up burning up relays frequently.

If the fan runs and the fuse is good, its very likely you just need a fan relay. This is a pulse width modulated relay, not the on/off clicker type you'd find in the fuse box. This unit is capable of infinite speed control. It gets very hot in operation, so its mounted to the body sheet metal to allow heat to dissipate through the sheet metal. The relay is mounted under the right headlamp held down with two 8mm screws. To get to it you have to remove the front bumper cover and headlamp bracketry to access the relay. These relays are pretty common.

Check and test this possible causes:
radiator fan ctrl rly circuit wire harn intermittent defect
radiator fan ctrl rly circuit wire harn observable defect
radiator fan relay ground circuit open
rad fan relay control circuit open
radiator fan relay control circuit short to ground
rad fan control relay defective
PCM defective

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Dec 19, 2011 | 2000 Jeep Grand Cherokee

1 Answer

1999 Jeep Cherokee Sport wont shift into overdrive P1491


P1491 - Radiator Fan Control Relay Circuit Open Or Shorted

When monitored: with the ignition key on, battery voltage greater than 10.0 volts and
the pcm requests the radiator fan to be turned on.
Set condition: an open or shorted circuit is detected in the radiator fan relay control
circuit.

Possible causes
radiator fan ctrl rly circuit wire harn intermittent defect
radiator fan ctrl rly circuit wire harn observable defect
radiator fan relay ground circuit open
rad fan relay control circuit open
radiator fan relay control circuit short to ground
rad fan control relay defective
pcm defective

Check ot and keep us updared.

Oct 15, 2011 | 1999 Jeep Cherokee

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Code p1491 on a dodge caravan


Trouble code P1491 means: Radiator fan relay control circuit

Feb 28, 2011 | Dodge Caravan Cars & Trucks

4 Answers

What does the diagnostic test code P1491 means?


Hello jhonney21,

The P1491 is Radiator fan control relay circuit code. It is set if an open or short circuit is detected in the radiator fan relay control circuit.

Regards,
netvan

Feb 25, 2011 | 2001 Chrysler Voyager

2 Answers

P1491 diagnostics code for 2003 Jeep Grand Cherokee



Trouble Code: P1491 You PCM does not sense current to radiator fan when it turns it on. Is the fan coming on or not? Usually not when you have this code. Problem can be with the fuse, relay, wiring or fan itself. First check the fuse. If good, next try swapping the relay with another one in the engine compartment relay box, such as the horn relay.
Let the car warm up and see if the fan will come on. If yes, get a new relay. If not, either use a test light to see if there is voltage at the fan connector when the engine is on and hot, or else test the fan motor by hotwiring it to the battery. If none of this works, please get back to me for how to troubleshoot the wiring.


Radiator Fan Control Relay Circuit Malfunction
Possible Causes:


Radiator fan control relay circuit is open or shorted to ground Radiator fan control relay circuit is open (test power to IGN) Radiator fan control relay is damaged or has failed PCM has failed

Nov 10, 2010 | 2003 Jeep Grand Cherokee

1 Answer

Getting code P1491 can't find the switch. Have looked everywhere. The fender is off and still can't find. 1999 Jeep cherokee classic 4.0 with mfg date of 10/1998. I know this is close to when they...


P1491 Radiator fan relay control circuit
i remember someone else asking this question and another expert said it was behind the bumper ?? ,right looking in the dreaded haynes book and its right side ,no thats a 98 model a 99 model is left side next to vacumn tank ,earlier model its under behind the battery

Nov 02, 2010 | 1999 Jeep Cherokee

1 Answer

P1491


P1491 is the radiator fan control circuit. I would start w. the simple things, like fuse, then you should check for current at the connector for the fan. If nothing, then the switch, then the relay. The switch typically screws into some portion of the water system and has a two wire connector. The relay is typically remotely located and not located in the fuse/relay box. <!-- from fixya rte -->

Aug 14, 2010 | 1999 Jeep Grand Cherokee

1 Answer

What can happen to my 2000 jeep cherokee ,with that code p1491?


P1491 code, You have a problem with the cooling fan relay. Do not drive this vehicle very far. If it has a Temp Guage keep an eye on it and don't overheat it. Possible engine damage could result. The relay is the most common cause for that code with a no fan operation condition.
The location of this relay. It's in the right front of the engine compartment. Kind of behind and below the RF headlamp and in front of and below the fuse box.
Easy to replace, just unplug it and plug the new one in.
.

May 04, 2010 | 2000 Jeep Grand Cherokee

1 Answer

Would not shift in to drive or reverse then lights interior flash


According to the fault code, there is no signal from the vehicle speed sensor to the OBD computer. A P1491 code is the radiator fan control circuit. I sounds like you may have an electrical problem that is causing a bunch of false readings. Have the computer reset and try again. You can get all of the fault codes at http://www.wjjeeps.com/faultcodes.htm#0500 Don't forget top rate this solution!!!

Mar 13, 2009 | 2000 Jeep Cherokee

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