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PCM not working on 2000 Jeep Cherokee 4.0 engine.

I hooked up a manual switch for the electric fan for cooling engine . With a fuse. Could this have shorted out my pcm Main cmputer on my 2000 Jeep Cherokee . 4.0 engine

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  • Richard Scordino May 11, 2010

    If you tapped into the fan power wire without unplugging it from the harness, it's possible to damage system, but I would think at best it would damage the relay. (the way they wire these things though nothing would surprise me) Is your jeep not starting now? Have you done or tried to do a code check? What were the results?


5 Suggested Answers

  • 1 Answer

SOURCE: 2001 jeep grand cherokee no start, no cam signal or ASD control from pcm


Posted on May 15, 2009

  • 7 Answers

SOURCE: where is the pcm on 1997 jeep grand cherokee 6 cyl?

I don't think the PCM is your problem, is the check engine light on? It could be you idle air control motor this is located on the throttle body, but because this happens while driving I am thinking you will need to replace your crank shaft position sensor it is located on the transmissinon bell housing it is very hard to replace without the correct tools. If the check engine light is on take it to a local auto parts store and ask if they can check the check engine codes for you they usally will do this for free.

Posted on Jun 03, 2009

  • 6982 Answers

SOURCE: jeep grand cherokee stalls after warming up

You need to check components again when the engine is hot and in no-start condition, otherwise, you will get bad info...obviously whichever part is doing this works fine cold. ones that react most to heat are crank pickup, ignition coil and the fuel pump.(bad ones get hot and bind up)

Posted on Jun 07, 2009

  • 244 Answers

SOURCE: how do i reset my pcm on my jeep grand cherokee?

try disconnecting the NEGATIVE cable on the battery for 10-20 minutes. re-connect it. start the vehicle and drive it for a few miles to let the pcm reset. (make sure the key is off and out, just to make sure you don't fry something when you remove the negative-black wire cable!!). don't short it against the positive-red!
make sure the negative connector (on the cable) is isolated from the frame, or it will still be grounded! wrap some plastic around it, or something!
good luck!

Posted on Sep 22, 2009

  • 2984 Answers

SOURCE: where is the pcm located on a 1997 jeep cherokee

Removal & Installation

  1. Disconnect the negative battery cable.
  2. Remove the coolant reserve tank and disengage the three electrical connectors from the PCM.
  3. Remove the three PCM mounting bolts and carefully remove the PCM.
  4. Installation is the reverse of removal.

Posted on Apr 18, 2010

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Need schematic for 04 jeep grand cherokee. Looking for electric fan circuit

4L or 4.7?
click WJ in the box, free factor service manual.
chapter 8w, page 42-13 &14
not too exciting.. really, a fuse, relay2 and PCM at bottom


Oct 29, 2016 | 2004 Jeep Grand Cherokee

2 Answers

RADIATOR ENGINE COOLING Electric fan override 1996 Jeep Cherokee Sport

RAD FAN IT IS. Engine cooling fan.
redux 1, 1996 XJ, 4.0L engine.
Rad fan, only.
RAD fan on,with PCM wanting it OFF. bypass.

or want fan to run fording streams. NO.
ask your offroad buddies what fording streams means. (hint it's not FORD car)
We do this offroad so the fan blades dont crash and break off, as they hit deep water.
posted vast times the free schematic, off the FSM book. links.
then chapter 8w (wiring)
then fan in index.
then , easy no?
pdf page 19 is the real index.
PAGE exact. XJ.
8w 42-9 is relay,pdf page 223
so lets go there.
WIRE COLOR ANSWERED !! below. 1st page of 8w show what color codes mean on all jeeps made.
the DB-PK wire on the relay D13
if grounded by any switch turns on the relay and fan.
do not use 12v power there or say goodbye to PCM. boom. (it will blow it up)
even grounding it can... (avoid the $500+ mistakes)

the free FSM

pg 223 pdf page, chapter 8w,
Relay FAN. ECU runs it there are no thermal switches, the ECT readings do all this. and very well.
the coil has 12vdc power keyon, the other rlay pin is hot all time.bat pin
top right.

see my switch ?if you use center off version switch
mark center FORD
eg: normal(pcm), ford, BYpass (or active)
or normal, dead, force on.


the first image is the risky way... but some do that. just SPST switch. (2 pins toggle, id use the 3pin way)

May 29, 2016 | 1996 Jeep Cherokee Sport

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

Engine Cooling problem 2000 Jeep Cherokee 4 cyl

Although the 4 cylinder is too underpowered to have air conditioning in my opinion, it still shouldn't overheat within 10 minutes unless something is wrong. If your Jeep doesn' not overheat when you are driving WITHOUT AC on then your compressor might have a problem and causing the engine to work too hard to turn it.

But if it overheats without the AC on, then the first thing you need to do is check the cooling fan and see if it operates! There has been a lot of problems with the cooling fan relay on this model. If that isn't it, then move to changing the thermostat and checking the water pump.

Jul 03, 2011 | 2000 Jeep Cherokee

1 Answer

2002 Grand Cherokee Larado AC cooling fan (small fan in front of radiator fan) stuck and was running after car was switched off. I had to disconnect the battery to get it to stop running. When I tried to...

NO ENGINE STATED, SO on exact answers. 4.0L or 4.7L ???
The engine cooling and HVAC rules govern this (computer tables and logic)
the service manual cover that,
did you SCAN the PCM at the failure then scan it again after, no?
did you know some cars run the fans parked to prevent overheat soak damage to the engine and trans? all have hood sticker warning telling you to stay way from fans, , until fully cooled engine or pull battery neg lug for safety. just saying that so you are safe fiddling all cars.

the fan(s) run via truth tables, logic (computer)
if cold outside why run a fan?, and waste fuel and cause green house gasses for fun. or make noise for fun, answer it doesn't.
it runs the fan ONLY when needed, is the answser
and is very complex, the newer the jeep gets.

On most cars even as old as 1995 , the condensor fan control would stay off if ambient temps are below 50f. this is not new logic.
Chapter 24 covers HVAC. in The service manual SM.
not only that, you failed to test the AC per the SM and failed to scan the PCM to see if there are HVAC faults. causing this fan disablement's. on purpose.
this car come with 2 type HVAC, manual and ATZ (climate control fancy) the rules for each are not the same (potentially)
the PCM controls the radiator fan on the 4.0L with a relay.
so is 100% pure (ATZ/BCM/PCM) logic doing that.
the 4.7L has hydraulic motor powered engine cooling fan
as you many not know the A/C condensor rams hot AIR
to the front of the engine RAD and cause it to overheat
so the engine fan is very much part of this regulation system.
The AC will also shut down for many AC related errors
and will do so if the engine or transmission over heats.
Self preservation.
there are 3 , 4.0L systems, for fan control
clutch fan or electric and one has a PWM modulated fan control module (its a transistor not relay in this case)

her is what chapter 7 states
The pulse width modulated (PWM) radiator cooling
fan relay is located behind the front bumper fascia
below the right headlamp.
The PWM relay is used to control the speed of the
electric radiator cooling fan. It allows for multiple fan
speeds. This allows for improved fan noise and A/C
performance, better engine cooling, and additional
vehicle power.
PWM relay operation is controlled by the Powertrain
Control Module (PCM). To operate the PWM
relay, the PCM looks at inputs from:
† Engine coolant temperature
† Ambient temperature from the body controller
† Vehicle speed
† Transmission oil temperature
† A/C switch position (A/C request)

the SM does not list all rule and tests for this device.

here more quotes from your missing book
If an open or shorted condition has developed in
the relay circuit controlling the electric radiator fan
or fan control solenoid circuit controling the hydraulic
fan, a Diagnostic Trouble Code (DTC) can be set.
If the problem is sensed in a monitored circuit
often enough to indicated an actual problem, a DTC
is stored. The DTC will be stored in the PCM memory
for eventual display to the service technician.

fans stuck on quotes
1. Fan control sensors inoperative.
1. Check for DTC's. Verify sensor readings.
2. Fan control solenoid stuck 9on9. 2. Check fan operation speeds. Refer to fan
speed operation table.

3. Fan control solenoid harness
3. Check for DTC 1499. Repair as required.
4. Transmission temperature too high.
4. Check for transmission over temp. DTC.
5. Engine coolant temperature too high.
5. (a) Check coolant level. Correct level as required.
(b) Thermostat stuck. Replace thermostat.
(c) Water pump failed. Replace water pump.
(d) Coolant flow restricted. Clean radiator.
(e) Air flow over radiator obstructed.Remove

the 4.7 liter engine the fan speed is base on above
and says, A/C system pressures.
the 4.7 then can can run at 500 rpm even when OFF. (SM)

now how to test the fan.
get engine hot, (drive 10miles say)
then park, and lest engine idle until the engine overheats
it will (but not in alaska, dig?)
and then the fans come on at bout 225f .. (about this is ball park)
electric fans
if using a 4.7L say so, its totally DIFFERENT

Mar 15, 2017 | 2002 Jeep Grand Cherokee

1 Answer

My cooling fan stays on my 2000 jeep cherokee. Even with the ignition key off.

That is normal, the system is designed this way to prevent the overheating of the engine's head when you shut down the engine without allowing it to cool itself to an acceptable temperature.

Jun 19, 2010 | 2000 Jeep Grand Cherokee

1 Answer

I have a 2003 Jeep Cherokee Laredo, 6 cyl, which has a 2 year old radiator, changed thermostat, water pump, the fan runs, and still overheats to the point the engine raddles and turns off. The radiator is...


Apr 19, 2010 | 2004 Jeep Grand Cherokee

1 Answer

97 jeep cherokee electric fan problem

sound like coolant temperature sensor is open or not working.scan it to see when engine get operating temperature when coolant temperature get 190 degrees the coolant temp sensor should show 190 degrees if it shows 80 degrees or lower it not working replace it.the coolant sensor control coolant fan.when it gets hot it resistance changes or lower.the pcm grounds it .then cooling fans will run.

Jun 17, 2009 | 1989 Jeep Cherokee

1 Answer

Over heating in stop and go traffic-1998 jeep cherokee 4.0 litre

If the electric cooling fan is inoperative, check the 15A fuse in the junction block and the 40A fuse in the Power Distribution Center (PDC) with a 12 volt test lamp or DVOM. Refer to the inside of the PDC cover for the exact location of the fuse.


Apr 25, 2009 | 2000 Jeep Grand Cherokee

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