Question about 1999 Jeep Grand Cherokee

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My cooling fan has no power even when wired directly to ignition.

When I first got my Cherokee 5 years ago, I had to replace the PCM within a month. Since then I've had to replace the fan relay at least once a year. Now my cooling fan has quit working, even after replacing the fan relay again and installing a new thermostat. It was wired directly to the ignition and worked sometimes, but is now completely dead. I'm not mechanically inclined so I have no idea exactly what parts I'll need to replace the fan. Does it come as all 1 kit? Could it be anything else other than the fan just fried out?

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  • Sarah Feb 22, 2012

    It's 4WD, 6 cyl, no tow package


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You can test ur fan with running" leads" or wires. a + and- from fuse box straight to fan wires, putting a on and off switch in between. its to check is fried or not. switch in line really not needed but it works

Posted on Feb 22, 2012

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2006 Chevrolet Trailblazer I6 suddenly began overheating at idle. Parts replaced within the last 2 months: Fan clutch, Tstat, radiator, radiator cap

How about the water pump ? Who replaced the parts ? A qualified repair shop ? Were codes checked ?
The PCM controls the electro-viscous fan clutch engagement. The PCM regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the commanded state of the fan clutch increases, so does the ON time of the relay. This ON time directly effects the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.
The fan has the ability to create a feedback signal, so the PCM has an actual fan speed input. This is done with a hall effect sensor internal to the fan clutch. The PCM supplies a 5-volt reference and a low reference to the hall effect sensor. The hall effect sensor returns a signal pulse through the cooling fan speed signal circuit in response to the relucktor track passing by the magnetic field of the hall effect sensor.
Was electrical tested before fan clutch was replaced !

Sep 29, 2016 | 2006 Chevrolet Trailblazer

1 Answer

Over heating cant find cooling fan relay

Gas or Diesel?
check fuses first! then scan it, the PCM will set DTC errors
if power feeds to the fan are dead, not scanning cars first is a travesty to (labor, time, parts wasted etc) even $10 scan tool works on our USA cars this year.

first off there are 2 systems.
and you never said what engine.
no engine, we must guess.
why work on any car, not knowing whats under the hood.
cylinder count 6,
displacement. 4.0 (wild guessing )
at the least. the big engine has the Hydr. system only.
wj jeep

4.0L or 4.7L engine.
ill answer for 4L , 5million sold.
TEST 1 (fan) parked and ran and purposefully overheated
this is a SOP FSM test , to see if the fan trips at the correct temperature !
if the fan does not work, parked, and overheating there are only these things wrong. ( any volt meter finds this easy)
1: ECT not showing overheat, to PCM ( use a scan tool !!!)
2: PCM cant see ECT , wires bad to ECT. sensor.
3: PCM fails to close relay (volt meter checked) due to above.
4: relay bad, or missing or wires to it bad. coil must be 12vdc hot.
5: relay output at 12vdc but fan dead, that is a dead fan, (hot)

in all cases bad wires and fuses and connections bad.
the 4.0L engine fan is a hybrid, has electric fan and thermal fan on front of water pump. so there are 2 tests.


its all there.
cav 13/14 PDC socket is it.

open hood, open lid, see lid words, its there. fan.


Mar 18, 2015 | 2002 Jeep Grand Cherokee Limited

1 Answer

How do I fix Diagnostic code 351

1. Check for power to the ignition coil when cranking.

2. Check continuity between the Powertrain Control Module (PCM) and the coil on the coil ground circuit wire.

3. Check connections at the coil and at the PCM.

4. If good, replace the ignition coil.

5. If the problem is still there, replace the PCM.

Jun 26, 2012 | 1997 Jeep Grand Cherokee

2 Answers

My 98 cherokee classic sport is overheating when it idles even if it is just a long red light. I have replaced the water pump and flushed the system and replaced the thermostat about 4 months ago. The...

It could be the fan clutch not engaging which will not pull air through the radiator, it may still appear to be spinning but it could not be at the correct RPM for adequate cooling. Hope that helps.

Aug 05, 2011 | 1998 Jeep Cherokee

1 Answer

I have a 1997 Ford Thunderbird. Upon turning the ignition key the cooling fan turns on and the car will not start. There is nothing you can do to make the car start until the cooling fan turns off which...

I would hate to tell to replace any parts without doing some testing , The cooling fan is controlled the PCM - engine computer through the CCRM - constant control relay module . The only thing i can would suggest is you have it hooked up to factory scan tool to check for DTC'S - diagnostic trouble codes an have scan data looked at . Different sensor inputs to the PCM , ECT - engine coolant temp sensor, IAT - intake air temp etc.... If there are no codes ,check power an ground circuits of the PCM . If the cooling fan stayed on all the time i would say the CCRM was bad , still could be , but with out testing this is just a guess . Do you know how to do automotive electrical testing using a test light , volt meter ? How to read an use a wiring diagram ? You can find free wiring diagrams here Enter vehicle info . year , make , model an engine ! Then under system click on engine , then under subsystem click on cooling fans . Good luck !

Apr 10, 2017 | 1997 Ford Thunderbird LX

1 Answer

The fan motor quit sons replaced the cooling fan they hooked up the black wire and yellow wire were they belong but they ran a hot wire from the battery to the green wire. then the wipers and ac...

Step 1 - Remove green wire
Step 2 - Check for blown fuses
Step 3 - Pray the PCM is okay ;)

Adding wires to a car to boost performance in some way, whether to the cooling fan or to the fuel system may have worked 30 years ago, but it seems like the only mechanical thing in a car built after '83 is the engine. Causing power surges, feedback and power draws can and often will do more harm than good. If there's a problem with the cooling fan motor, even after replacement, the motor may never have been the problem. There's the coolant temp sensor, cooling fan relay, PCM..... too many possibilities to just throw parts at.

Let's just look at GM's, for an easy example. In the old days, pulling the positive cable off the battery was a sure-fire way to diagnose an alternator/generator. Nowadays, pulling the positive cable while the engine is running can cause a spike in the charging system so severe, it can fry the PCM. Fry the brain.

We can still service these vehicles at home, but we have to be careful. Where we used to adjust the choke to cure a cold start problem, now it may be the engine temp sensor. It may be the mass airflow sensor. It may by the throttle position sensor, map/baro sensor.....

Let me know what comes from this. Hopefully, no damage was done, and removing the wire and replacing any blown fuses will do the trick. Best of luck!

May 22, 2010 | 1995 Ford Escort

2 Answers

If i hooked a hot wire with a switch up to my dual radiator fans with a switch, would that affect my 1998 dodge neon, 2.0 L, manual transmission, dohc to have a problem dying? I have replaced the cam,...

PCM is difficult to diagnose without proper scan tool, commanding components and verifying pcm ability to control them. Watching data as compared to actual inputs, these eliminate all but the pcm. As for the cooling fans, I have seen cooling fan related issues cause the pcm to failsafe. Causing stalling, low power, and rough idle. Why did you install a manual switch. If pcm is commanding them on and the fans, relays, and circuits are good then your circuits are good. I would look into why the fans are not operational and this may lead to the diagnosis you need.

Sep 09, 2009 | 1998 Dodge Neon

1 Answer

Fan still doesn't work.

You may want to trace that relay power wire back. There may be a fuse under the dash that supplies power to it, and likely another in the distribution center. I'm fairly sure the pcm supplies the ground signal to the relay.

Jul 25, 2009 | 2001 Jeep Grand Cherokee

1 Answer

Overheating engin when at idel, fan not working

does both the hoses get hot bottom and top? this will tell you if theres flow through the radiator. If you have a voltage tester test the wires on the fan connecter check there is current going to the fan if so replace the fan its a common problem as previously stated. 
if there is no power to the fan when the vehicle should be turning it on i.e. its hot enough check the fan relay under the hood.

Nov 23, 2008 | 1999 Jeep Grand Cherokee

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