8 2003 Jeep Grand Cherokee 4.0 Fan Relay Test

April 17, 2011 Updated: December 18, 2022 Past: Abraham Torres-Arredondo Article I.D.: 268

This tutorial will assist you to name the Pulse Width Inflected (PWM) buff relay on the 1999-2003 Landrover 4.0L Grand Cherokee SUVs and/or the codes P1491 (Radiator Fan Control Relay Circuit).

The dealer, at the time of this writing, will send you $95 (US) to diagnose it. But if you have more clock than money, you can easy diagnose it yourself, and I'll show you how.

Testing the devotee relay is easy, the hardest part is getting to information technology, since Jeep in all its wisdom, set the lover relay behind the right side (passenger lateral) of the battlefront bumper and you'll probably make to get rid of IT to access it.

You can pay Jeep an gir and a wooden leg to do it, operating theater you give notice, with my serve, name and vivify the come forth yourself, save that money and spend information technology on something like tools.

You can find this tutorial in Spanish present: Cómo Probar El Relé PWM del Ventilador (4.0L Jeep) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

1. 1999, 2000, 2001, 2002, 2003 4.0L Landrover Grand Cherokee.

Kin WIRING DIAGRAM:

1. Radiator Fan Motorial Circuit Wiring Diagram (1999-2003 4.0L Landrover Grand Cherokee).

Important Tips

TIP 1: The way I've designed the Landrover PWM lover relay test, you'll need a scan tool that can read live data (non a code reader), since you'll need to keep an eye along the engine's coolant temperature with it.

You do not need the Jeep manufactory glance over tool, just a generic run down tool that you stern sponsor your localized auto parts store or online and a multimeter. Now contingent your level of 'wrenching get', you can modify this test so that you can do it without a generic scan tool (and I leave this up to you).

TIP 2: IT's very important that you begin with a cold engine. If you have a scan tool, verify that the engine coolant temperature (Electroshock) valuate is under 190° F. If the engine has been running for an extended historical period of time, let information technology cool down for about 1 hour or more.

TIP 3: Before you jump into the tests, have a look at and register the entire article so that you'll cognise what the test is all about and what you'll need to do.

TIP 4: The very first thing that you need to test/verify, is the fan. You need to physically see it come through along past directly applying 12 Volts to that and if the buff causative does come on, calculating its amperage draw (and I'll show you how).

TIP 5: Too, you're not gonna' find any 'remove and replace' type instructions since the article is all about the diagnosing the relay, not how to remove and replace it. So you may have to buy a reparation manual of arms operating theater do further research online.

Symptoms Of A Bad PWM Fan Relay

The most obvious symptom of a bad PWM fan relay is that your Jeep is gonna' overheat.

You'll also see one surgery all of the following symptoms as the engine overheats:

1. The electric radiator fan efferent does non come on.
2. Coolant bubbling impossible of the coolant reservoir.
3. Temperature gauge on the instrument cluster is maxing out.
4. Check railway locomotive light (CEL) is on and:
   1. DTC P1491 stored in the computer's memory

If your Jeep overheats beyond a certain point, you risk blowing the head gasket and/or cracking the cylinder head word.

Thankfully, testing the PWM fan relay can be easily done right at home, without the need of taking information technology to the Jeep house.

8 2003 Jeep Grand Cherokee 4.0 Fan Relay Test

Source: https://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-pwm-relay-1