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Fixes for Jeep Grand Cherokee 1999 - 2004 (WJ)



Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Coolant loss/have to add coolant periodically. Related symptom: Odd smell from A/C dash vents. Passenger side carpet may be wet/moist.

Cause:  The heater core is leaking.

Resolution:  Replace the heater core. Alternative/temporary repair: Locate the 2 heater hoses going to the firewall underhood. Cut the hoses and splice them together. Hose splices are available at any auto parts store. Vehicle will have no heat, but A/C will still operate.

Details:  Heater core is leaking. Inspect the HVAC black plastic case in the passenger side footwell for evidence of leak. Coolant will run down the case and under the carpet. Leak is usually slow/minor.

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Vehicle:  1993-1998 (ZJ) Jeep Grand Cherokee with 4.0L engine, 1999-2004 (WJ) Jeep Grand Cherokee with 4.0L engine, 1997-2001 (XJ) Jeep Cherokee with 4.0L engine, 1997-2006 (TJ) Wrangler with 4.0L engine.

Concern:  Engine cranks but will not start. May have died while driving. Related symptoms: Fuel gauge shows 'empty', however the fuel tank is not empty. Volt gauge is all the way to the left (low), but the battery is not discharged.

Cause:  The CKP (crankshaft position) sensor is shorted internally. Turn the key off. Unplug the CKP sensor and retest for proper gauge operation.

Resolution:  Replace the CKP sensor to correct.

Details:  Scan tool will show 'no response' to PCM (engine computer). This is why the fuel gauge and volt gauge are inoperative. The PCM is not functioning, so the fuel and voltage data is not bussed to the instrument cluster. When the the CKP sensor shorts internally, the PCM will not function. The connector is located on the right side of the engine, near the rear of the engine block. The CKP sensor is located on the left side all the way in the back. Usually it must be replaced from under the vehicle. This is a fairly common problem.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  All 4 power windows inoperative.

Cause:  The BCM (body control module) is electrically "locked up".

Resolution:  Disconnect the battery for about 10 minutes. Reconnect and retest for proper operation. This should reset the BCM.

Details:  Diagnosis with a scan tool should be the first step in a case such as this. A module scan with a DRBIII scan tool would have indicated that all modules were functional except the BCM. If disconnecting the battery does not resolve the issue, further diagnosis will be necessary.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Power windows inoperative. Possibly all switches on driver door inoperative. Interior lights may not come on when driver door is opened.

Cause:  Driver door module (master switch assembly) is not communicating.

Resolution:  First, disconnect the battery for 10 minutes, then reconnect and retest for normal operation. This may 'unlock' the driver door module. If unsuccessful, inspect the wiring going from the driver door to the body. Carefully loosen the black rubber boot and pull back. You will probably find (1) or more broken wires. Replace the door wiring harness, or repair the wires.

Details:  -

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Vehicle:  All vehicles (TJ) (WJ) (RS) (XK) (WK) (RS)

Concern:  Loud noise/vibration from interior fan (for A/C heat)(HVAC) especially when on high speed, usually speed 3 or 4.

Cause:  HVAC fan (blower motor) is out of balance. Usually caused by fan sucking in leaves or other debris.

Resolution:  Remove the blower motor and inspect/clean the fan blade (squirrel cage type). Normally the blower motor is located under the passenger side dash. Most are easy to remove, held in with 3 screws, either Phillps or T20 torx.

Details:  -

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Vehicle:  Jeep Grand Cherokee (WJ) with 4.7L engine. Dodge products with 4.7L engine.

Concern:  The check engine light is on. Has any or all of the following DTCs: P0201 injector#1 control circuit, P0202 injector #2 control circuit, P0203, P0204, P0205, P0206, P0207, P0208. Fault is probably intermittent, and there is possibly no driveability problem associated with it.

Cause:  A fault in the TPS (throttle position sensor) causes signal noise, which the PCM interprets as an injector circuit fault. This condition is very rare.

Resolution:  Replace the TPS to correct the condition.

Details:  -

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Vehicle:  All Chrysler/Jeep/Dodge (WJ) (AN) vehicles with 4.7L 8 cyl engine.

Concern:  Idle fluctuation. Engine idle speed goes up and down. May be intermittent. Idle speed will rise to about 1200 rpm and settle back to normal. More noticeable in park or neutral.

Cause:  The TPS (throttle position sensor) is beginning to fail. The closed throttle voltage reading is not accurate/fluctuates.

Resolution:  Replace the TPS located on the throttle body.

Details:  -

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Long crank time. Engine is hard to start. May require 2 or 3 attempts to start engine. Engine will always start. Not to be confused with a true no-start condition. This assumes the battery is OK and the cranking speed is normal.

Cause:  An o-ring seal inside the fuel pump has deteriorated and is leaking. This is an INTERNAL leak. No fuel will leak outside the vehicle.

Resolution:  Lower the fuel tank and replace the fuel pump assembly.

Details:  This would be a good time to replace the fuel filter also.

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Vehicle:  All vehicles with 3.7L and 4.7L engines. (WJ) (KJ) (DR) (AN) Jeep Liberty, Grand Cherokee, etc.

Concern:  Engine is overheating after cooling system repairs. Engine is overheating after the radiator was drained/refilled for maintenance.

Cause:  The cooling system was not properly bled. There is an air pocket trapped, not allowing coolant to circulate.

Resolution:  Allow the engine to cool. Remove the bleeder screw. Look where the upper radiator hose attaches to the engine for the bleeder screw. It requires a 10mm hex (Allen) type tool. Sometimes the screw will be very tight. You will need to use a high quality tool and possibly considerable force to remove it. Remove the radiator cap and fill the cooling system until coolant comes out of the bleeder screw hole. Reinstall the bleeder screw. You must use thread sealant to prevent a leak. Put the radiator cap on and retest.

Details:  If the bleeder screw will not come out, remove the upper radiator hose at the engine just enough for coolant to come out while filling the system. This will work in a pinch.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee.

Concern:  Engine is overheating, mostly at stoplights. Engine does not overheat while driving. A/C will not be very cold at stoplights. This assumes the coolant is full.

Cause:  The electric radiator fan is inoperative.

Resolution:  Replace the electric radiator fan AND the radiator fan relay to correct. Trust me...been there, done that. If one is faulty, replace both.

Details:  The radiator fan relay is a solid-state (no moving parts) electronic relay. It is located directly under the right (passenger side) headlamp. You will need to cut an access hole in the plastic support panel under the headlamp to access the relay.

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Vehicle:  1993-2004 (ZJ) (WJ) Jeep Grand Cherokee with 4.0L engine.

Concern:  Check engine light (MIL) is on. Has P1281 engine is cold too long. No driveability symptoms. Engine is running normally.

Cause:  The thermostat is stuck open. The thermostat in many cases may come out in several pieces (falling apart).

Resolution:  Replace the thermostat and gasket and refill the cooling system.

Details:  The PCM (engine computer) performs a rationality test on the engine cooling system. It measures engine temperature vs. engine run time. If the engine warms up too slowly, P1281 will be set and the MIL will be on.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  The A/C blows but is not cold (compressor will not engage). The instrument cluster backlighting is on at all times (with key on). The instrument cluster gauges are inoperative. Power windows are inoperative.

Cause:  An electrical fault is disrupting the PCI Data Bus. The various modules cannot communicate with each other.

Resolution:  This is not easy to resolve, however I will give you a few tips. Use a digital volt meter to measure the voltage on pin #2 of the data link connector. The data link connector is located under the driver side dash near the fuse box. It is the connector that the scan tool plugs into. Pin 2 is the PCI Bus circuit and should be a white/violet wire. The voltage with key on should be between 0 and about 2.5 volts. It will fluctuate as the modules communicate. If the voltage is too high, say 6 or more volts, you have found the cause. Unplug modules one at a time until the voltage drops and things start working again.

Details:  Module examples are: PCM (engine computer), TCM (transmission computer), BCM (body computer), ABS (antilock brake module), instrument cluster, air bag computer, driver door module, passenger door module, radio, amplifier, a/c control head, overhead console computer. Sometimes disconnecting the battery for a few minutes will resolve a module-based PCI bus issue, though it may be temporary. It is also possible for the PCI bus circuit to be shorted to voltage or ground. Usually it is a module problem rather than wiring.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Ongoing problem with brake bulbs. One or both brake bulbs is inoperative or too dim. New bulb does not solve problem, or seems to be only a temporary fix.

Cause:  The 'circuit board' that holds the bulb sockets is warped or burned, causing high resistance.

Resolution:  Replace the complete tail lamp assembly. These are available aftermarket for a very reasonable price.

Details:  Bad design. Substitute a 3157 LED bulb to prevent this from happening again. Check ebay for the bulbs. The heat from a conventional 3157 bulb causes the circuit board to warp.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  One or more power door locks are inoperative. Power locks make loud 'screeching' noise.

Cause:  The power lock actuator is failing. The lock actuator is inside the door latch. The door latch is the part that physically latches the door closed. It is on the rear of the door.

Resolution:  Replace the latch to correct.

Details:  -

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee with 4.0L engine

Concern:  Possible no start and/or check engine light. One or more blown fuses in power distribution center underhood.

Cause:  Wiring harness at rear of engine is shorted to ground.

Resolution:  Inspect and repair wires as needed. Armor the harness to prevent future problem. A piece of heater hose makes an excellent gaurd for the harness.

Details:  Inspect the harness at the rear of the valve cover. The harness will rub on the cylinder head bolt.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Power window inoperative. The window is down and will not go up. Can hear the window motor operating.

Cause:  The window regulator cable is broken.

Resolution:  Replace the power window regulator to correct.

Details:  The new regulators from the dealer are heavily revised. I have never seen one of the new style regulators break. I have installed lower-cost aftermarket regulators that worked just fine. Replace the door panel plastic clips as needed.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee (with manual HVAC system)

Concern:  HVAC air comes out of defrost vents only.

Cause:  Loss of vacuum supply to HVAC system.

Resolution:  Repair or replace the vacuum hose as needed.

Details:  Inspect the vacuum hoses to the intake manifold (4.0L engine). It is common for the HVAC vacuum supply hose to soften and come off the manifold.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Oil pressure gauge is inaccurate. Gauge reads 80 psi (or needle is all the way to the right if it has L - H scale) when engine is running.

Cause:  The oil pressure sensor is failing.

Resolution:  Replace the oil pressure sensor.

Details:  Requires a special tool.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Rattle noise from front suspension, over bumps.

Cause:  Front shocks are loose due to worn bushings.

Resolution:  Replace the front shocks.

Details:  Check the upper shock bushings for lateral movement.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee with AZC (automatic zone control).

Concern:  Interior fan for A/C and heater is inoperative. May be intermittent.

Cause:  The electrical connector to the blower control module (AKA blower resistor) has overheated and burned.

Resolution:  Replace the blower resistor and splice on a new connector. See dealer for parts.

Details:  -

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee with full time 4 wheel drive.

Concern:  Noise while turning sharply in parking lot. Rubbing noise/sensation.

Cause:  Low fluid, or incorrect fluid in the transfer case.

Resolution:  Drain and refill the transfer case. Inspect for leaks.

Details:  I have seen several cases where the fluid was extremely low with no significant leak present, indicating a lack of maintenance. A special fluid is required for full time 4WD tranfer cases. Part time units usually require ATF (automatic transmission fluid.)

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee with limited slip differential(s)

Concern:  Noise while turning sharply in parking lot. Rubbing noise/sensation.

Cause:  Lack of limited slip additive in differential(s)

Resolution:  Remove and clean differential cover. Reinstall/reseal cover. Add full bottle (4 oz) of limited slip additive. Fill differential with 75W-140 synthetic gear oil. Test drive vehicle to re-check for noise.

Details:  -

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  The passenger front carpet is wet. A/C condensate (water from A/C operation) is leaking inside the vehicle.

Cause:  A/C condensate (water from A/C operation) is leaking inside the vehicle.

Resolution:  Locate the A/C drain tube. It is located on the passenger side lower firewall, in the engine compartment. You will see a black plastic tube sticking out about 1.5 inches long. It is easy to see with 4.0L engine. With 4.7L engine, you will have to access it from below. Purchase a rubber drain tube #56000724 from dealership parts dept. Install the tube onto the exiting drain tube and clamp it with a tie strap. (The rubber drain tube should point down). Start the engine and turn the A/C to full cold/high fan. A small amount of cool air should flow from the drain tube. After a few minutes, water will begin to drip from the drain tube.

Details:  This will solve your problem for about $5.00. Wet carpet needs to be lifted up and dried out. The padding under the carpet will NEVER dry out on its own. Failure to dry it out properly will result in odor, rusted body and wiring damage.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Snapping sound when opening driver or passenger front door.

Cause:  Door check strap is worn.

Resolution:  Replace the door check strap to correct.

Details:  Requires door panel removal.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  Speakers sound terrible. Distorted.

Cause:  One or both dash speakers are coming apart. The paper is rattling against the speaker frame.

Resolution:  Replace the dash speaker(s) to correct.

Details:  -

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee.

Concern:  Vibration while braking. Pulsation is felt in brake pedal and/or steering wheel.

Cause:  Brake rotors are warped. Very common problem.

Resolution:  Resurface or replace the front brake rotors. Inspect the brake pads.

Details:  Normally brake pulsations are caused by the front rotors, which are more likely to warp. Of course, the rear rotors can warp also in some cases. Rear warpage will probably not be felt in the steering wheel.

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Vehicle:  1999-2002 (WJ) Jeep Grand Cherokee

Concern:  Vehicle pulls to left or right. Brakes seem to stay applied. Front brakes getting too hot. Burning smell from front brakes. Usually happens after front brake job.

Cause:  Front caliper(s) failure. Caliper(s) are sticking.

Resolution:  There are two styles of front caliper. Look at the rear calipers. See the thick wire on the outboard side? (It is a type of spring for caliper retention). Check to see if the front calipers have the same type of spring (it will be larger, but same basic shape). If the front calipers have the spring, they are the old style and need to be replaced with new style calipers. The old style have a tendency to stick after a brake job.

Details:  There is a repair package available which includes 2 new calipers, front pads, and sealing washers for the brake lines. Check your local dealer. New-style calipers do not have the wire spring.

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Vehicle:  1999-2004 (WJ) Jeep Grand Cherokee

Concern:  One or both exterior mirrors are floppy and loose. Will not stay in position.

Cause:  The folding hinge has broken.

Resolution:  Remove mirror. Drill 2 holes. Install trim screws to lock the mirror in position. Re-install mirror.

Details:  Cheaper than replacing!

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Vehicle:  All vehicles. (JK)(ZJ)(CS)(JC)(TJ)(XJ)(PT)(KJ)(KK)(KA)(AN)(ND)(DR)(DS)(WJ)(WK)(XK)(LX)(LH)(FJ)(JR)(JS)(RT)(RS)(NS)

Concern:  The MIL (check engine light) is on. The scan tool reveals DTC P0601 PCM internal controller failure.

Cause:  The PCM (engine computer) has an internal fault.

Resolution:  Replace the PCM to correct.

Details:  This is an easy diagnosis. When P0601 is present, the solution is always to replace the PCM. There is no other possible cause. Normally the vehicle is still driveable.

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Vehicle:  All Chrysler, Jeep, and Dodge vehicles. (JK)(ZJ)(CS)(JC)(TJ)(XJ)(PT)(KJ)(KK)(KA)(AN)(ND)(DR)(DS)(WJ)(WK)(XK)(LX)(LH)(FJ)(JR)(JS)(RT)(RS)(NS)

Concern:  Alternator failure. The alternator (generator) is not charging. Electrical problems.

Cause:  -

Resolution:  Hold on for a minute. Alternator failures are extremely rare on Chrysler, Jeep, and Dodge. You need to rule out the battery, wiring, and PCM first before replacing the alternator.

Details:  The alternator is controlled by the PCM (engine computer). Again, true alternator failure is very rare. In ten years as a dealer service dept tech, I have replaced maybe five alternators.

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