20 Most Recent 1999 Jeep Wrangler Questions & Answers

If the engine cranks and cranks but never starts ? It's almost always the CPS.

The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the CranKshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when engine gets hot, but works again (and will test as “good”) when it cools back down.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables and replace as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU will behave oddly until you remedy this.

Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- Fuel gauge and voltage gauges may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump will run and prime for 3-5 seconds.

If the CPS/CKP is failed sometimes the OBDII code reader cannot make a connection to the computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed.

Diagnostic steps to confirm the CPS is the cause of your no-start

You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now displays correctly, replace the CPS.

Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication.

CPS Testing

Crankshaft Position Sensor Connector (CPS/CPK)


TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines
1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.

The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector may be on the passenger side, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.


1999 Jeep... | Answered on Sep 03, 2019

You will need to scan the PCM for stored faults. The PCM will receive the resistance value from the fuel sending unit and sends this info via the data bus to the instrument cluster. There could be a wiring issue from the sending unit to the PCM, so I would do a resistance test on the wires to check for continuity.

1999 Jeep... | Answered on Jun 01, 2019

Hook up a scanner and find the problem. Make sure that the injectors are pulsing. Water could have blown a fuse.

1999 Jeep... | Answered on Apr 24, 2019

I think you could use this manual method instead.. My nephew used it to repair my car and it's perfectly fine now. Here's the website
he bought it from. www.reliable-store.com

1999 Jeep... | Answered on Mar 07, 2018

Check fuse 18 in the box under the hood. If yhat is good, suspect the crankshaft sensor. If you can scan the computer, send the trouble codes.

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1999 Jeep... | Answered on Feb 03, 2018

harmonic humming ( harmonic vibrations ) indicate a problem idler pulley bearing , water pump bearing , alternator bearing or power steering pump bearing It is not considered an ac compressor bearing because when the ac is energized that pulley bearing stops spinning when the shaft starts turning and you state that the hum persists with ac on or off

1999 Jeep... | Answered on Jan 20, 2018

Visit the on-line store, known as reliable-store, they have the repair manuals. I'm sure you will get the solution of your problem.
1999 Jeep Wrangler

1999 Jeep... | Answered on Dec 14, 2017

Due to the age of your jeep, You need to replace the fuel pump and filter along with replacing the water pump and thermostat as well as coolant temp sensor. Fuel supply and coolant flow and temp sensing is critical to Cold start (open loop) and warm up (closed loop) Idle function and fuel mapping. Change the air filter too.

1999 Jeep... | Answered on Aug 25, 2017

the pcm is suspect in that year jeeps. simple easy test. locate pcm usually on firewall passenger side under hood. 3 large cables going into it on most. start jeep. let it idle. wiggle one wire at a time. does it shut off?? bad pcm solder joints inside are broken. doesnt shut off?? another issue to be determined.

1999 Jeep... | Answered on Jul 17, 2017

not normally
there may be metal flakes in the filter in the reservoir so replacing it would be a good idea
don't bother repairing the pump, it will be more cost effective to get a new one
if short of cash , get a good unit from the wreckers/ junk yard

1999 Jeep... | Answered on Apr 06, 2017

rough idle is from faulty injectors or maf/vaf sensors or vacuum leaks
run the fault codes to determine the fault area

1999 Jeep... | Answered on Jan 05, 2017

manual trans or automatic, the are not the same.???????
so fix when not starting, afterwords that can be impossible
to fix this, scan it
the scan tool will tell why it lost spark
p03xx errors
do not play with CKP sensor,if you remove, it and not put it back like the FSM states, it will never start or be damaged
it has critical gap there. (see fsm exception)
there are 3 eCU inputs that kill spark
dead cmp
dead ckp'
and dead tachomter, ignitor signals,
all 3 , will kill the ASD relay dead, (6 ways) (scan it)
this fact , is why we scan ,and not guess.
if you install a new ckp , and do it wrong, its destroyed in some cases.

to read how to do it right (ckp)
read the free fsm

WE HAVE 100'S OF posts here,making the CKP install error.
click ignition chapter
8D-12 read page 13
one 2.5l has a special machined sensor that fits with out adjustment. if you read that page 13, it covers a/t and m/t
rules. (2 engines, 2 trans) rules.
and if you buy autozoned parts,they will sell you that wrong part
toss 4 sided coin bam fail.
One sensor has glued paper sensor gapper, that must be used.
CKP have gaps that must be correct. keep that in mind and all works out. via the FSM.
all none HALL sensors are like this, (tuned with a gap)]

only how done varies.

1999 Jeep... | Answered on Jan 29, 2016

This is a common failure on 1999-2004 WJ models with the AZC (Automatic Zone Control) system. The connector on the blower motor control module overheats, resulting in intermittent or no operation of the blower motor. Mopar released a connector harness repair kit to fix the problem. The damaged connector is cut off and new wires are spliced into place. Only the green wires from the kit are used. One end of each of the 3 green wires goes into the new connector end that is provided. When inserting the wires into the connector, the locking spring tabs should be on the bottom. There is a gray plastic retainer that is then installed around the three wires that were just inserted into the connector.

1999 Jeep... | Answered on Dec 03, 2015

i would think that it is an immobilizer symbol letting you know of a problem with the key in use
talk with a service dealer or have the fault codes read to see if there is an immobilizer fault

1999 Jeep... | Answered on Nov 08, 2015

read that on the door jam label .

1999 Jeep... | Answered on Oct 28, 2015

need to check the wiers going to the fule pump housing ok

1999 Jeep... | Answered on Oct 25, 2015

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