Question about 1996 Jeep Cherokee

1 Answer

Got jeep going, ran for two days then it would'nt start, this has happened several times. Checks I have done; fuses ok, no power at coil, no spark, checked all connections. I would like to test crank angle sensor voltage, and sensor also cam sensor with a dmm what should the readings be? I would also be grateful for any other suggestions, thank you!

Posted by Anonymous on

  • Anonymous Jan 26, 2011

    Appreciate your help. There is no positive voltage at coil with ignition on, what would you advise I do next?
    Having trouble finding fuse 20, is it near battery or near kick panel?. Am I looking for 20 or 20amp?
    All fuses seem ok. Thanks again :)

  • Anonymous Feb 05, 2011

    Hi thanks for your help .I checked fuse 20 ok ,the ASD relay seems to be operating when the ignition is turned on but shuts of within a few seconds checked with DMM. I changed the relay but made no diference in the operation. Checked harness between ASD relay and coil all ok would be very greatful for some more help thank you.

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1 Answer

Jeffrey Turcotte

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  • Jeep Master
  • 8,984 Answers

Hi, if you have no power at the coil, the sensors cannot cause that. Are you saying there is no positive voltage there or just that the timing pulses are not coming from the computer? Power is supplied to the coil by fuse 20 via the auto shutdown relay and the PCM. See diagram below. To answer your question, I've pasted some sensors tests below. The cam sensor signal is not generally used by the PCM for ignition timing but more for injector timing. If you are not getting ignition timing pulses, the crank sensor is suspect, as you have implied. If you are not getting positive voltage to the coil, suspect fuse 20 or the auto shutdown relay, or possibly the ignition switch itself. Please let me know if you have more questions, and thanks for using FixYa.


Crank sensor tests:

  1. Backprobe with a high impedance ohmmeter between the CKP sensor connector middle terminal and battery ground.
Got jeep going, ran for two days then it would'nt - jturcotte_189.jpg
  1. Verify that the resistance is less than 5 ohms. If the resistance is not as specified, repair or replace the wiring as necessary and continue the test.
  2. With the ignition ON and the engine OFF , backprobe with a high impedance voltmeter between the sensor connector middle terminal and either of the end terminals.
  3. Verify that a 5 volt or greater signal is present at one of the two terminals. If not as specified, repair or replace the wiring as necessary and continue the test.
  4. With the ignition ON and the engine OFF , backprobe with a high impedance voltmeter between the sensor connector middle terminal and the end terminal that did not have the 5 volt or greater signal.
  5. Crank the engine and verify that the voltage reading alternates between 0.0 and 5.0 volts or verify that the voltage reading is 2.5 volts (averaging voltmeters only).
  6. If the voltage readings are not as specified, the sensor may be faulty.


Cam sensor checks
  1. Make sure that the ignition is OFF , remove the distributor cap and turn the engine over by hand.
  2. Verify that the distributor shaft turns. If the distributor shaft does not turn, the engine must be checked for propGot jeep going, ran for two days then it would'nt - jturcotte_188.jpgration.

jturcotte_188.jpg


  1. Backprobe with a high impedance ohmmeter between the CMP sensor connector middle terminal and battery ground.
  2. Verify that the resistance is less than 5 ohms. If the resistance is not as specified, repair or replace the wiring as necessary and continue the test.
  3. With the ignition ON and the engine OFF , backprobe with a high impedance voltmeter between the sensor connector middle terminal and either of the end terminals.
  4. Verify that a 5 volt or greater signal is present at one of the two terminals. If not as specified, repair or replace the wiring as necessary and continue the test.
  5. With the ignition ON and the engine OFF , backprobe with a high impedance voltmeter between the sensor connector middle terminal and the end terminal that did not have the 5 volt or greater signal.
  6. Crank the engine by hand and verify that the voltage reading alternates between 0.0 or 5.0 volts.
  7. Install the distributor cap and crank the engine with starter. Verify that the voltage reading is 2.5 volts (averaging voltmeters only).


jturcotte_911.gif

Posted on Jan 26, 2011

  • 19 more comments 
  • Jeffrey Turcotte
    Jeffrey Turcotte Jan 26, 2011

    Sorry, fuse 20 is 20 amps. Should be labeled IGN or PCM--something like that. You may want to also check fuse 16, 15 amps, as it powers the relay coil. I would expect fuse 20 to be in the engine compartment, but fuse 16 may be inside by the brake pedal. Relay shoud also be under the hood--did you see it there? You can interrogate the relay socket to see what signals are present. That is the quickest way to troubleshoot the situation. Please see my tip athttp://www.fixya.com/cars/r6022358-relay...

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 06, 2011

    Hi, use your meter in the ASD relay socket to see if there are 2 hot terminals when the key is on. If there is only one hot terminal, the ignition switch is failing in the run position. You can test this by running a jumper from an accessory fuse to the orange wire that powers the relay. Such a jumper can be used temporarily to run the car, but you don't want to permanently have your coil on every time the accessories are turned on. A new switch is $34 at autozone. Please continue to reply if you have more questions.

  • Anonymous Feb 06, 2011

    hi i checked hot terminals there is power at 16 and 18 at ASD RELAY with key on .Im not sure where to go next . When i turn the key on there is power at coil for a very short time' then the ASD relay cuts out .I changed the relay made no diffrence,checked continuity from PMC C3 terminal and relay is fine.

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 06, 2011

    OK, you're doing a good job with the meter. I forgot to mention the other possibilities. So it sounds like the PCM is shutting you down. You can verify this by the lack of a ground signal in the relay socket. Put one of your meter probes to battery positive and probe the socket again with the other meter lead. If there is no sign of 12 volts, the PCM is turning off the relay. The usual cause of this is a passlock-type system. Let me look over the diagrams to see what kind of security system might be there or what other reason the computer may have for doing this.

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 06, 2011

    OK, I don't have a full set of diagrams, but I do see some discussion in the forums of a security system. Do you have a little indicator on the dash of a key with an "X" over it?

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 06, 2011

    What I'm going to suggest is a little risky, but not much. I don't know if you have a security system or not, but I don't see the harm in holding the ASD relay closed. So, since you have traced the signal wire from the C3 pin at the PCM, I suggest you cut that wire and connect the relay side of the wire to chassis ground. This should keep the relay closed. Then see if the Jeep will start and run. If it does, see if the engine light stays on. If not, you may just have an issue with a security system. If the engine light stays on, then get an OBD2 scan at your local parts chain and send me the trouble code. If you live in the US, most parts chains offer a free scanning service. This will help us see what is causing the PCM to turn off the relay. OK?

  • Anonymous Feb 08, 2011

    Hi thanks again for your help, had no luck i checked the ground signal on the C3 terminal to relay, funny thing is i have an earth but relay will not send power to coil. So i cut the line an sent the relay to earth i have power to coil but still will not start. I tried to get some codes by turning the key off an on 3 times the only code i got was 3 an 55 i dont know if thats much help.thanks again.

  • Anonymous Feb 08, 2011

    sorry forgot to mention yes there is a security system on the car

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 08, 2011

    Hmmm...I don't see a code 3 or 30, but 55 is refernce signal grounded. Did you ground the whole wire or just the relay side? You have to cut the wire and leave the computer side unattached. I think you're making progress here. At least you now have power to the coil. Next, are you getting sparks? Pull off one of the wires from a spark plug, stick a phillips screwdrive in it, and resr it on the engine where the shaft of the screwdriver is about 1/4 inch from engine metal. Crank the engine and watch for spark to jump from screwdriver to engine. Let me know what happens.

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 08, 2011

    Actually, I'm not clear on either code. The manual doesn't have a code list for 1996. I'm reading codes for other years. Let's ignore the codes and just get this Jeep started. I think you did right with grounding the relay coil wire. You may be very close to this thing coming back to life. Listen for the fuel pump--is it running? Check for spark and check to see if you can hear the injectors clicking. Look over my post here: http://www.fixya.com/cars/r5821173-doesn...

  • Anonymous Feb 09, 2011

    hi again yes the motor has no spark an i carn`t hear the fuel pump running or the injectors clicking . I found the immobliser box near steering collum could that be at fault or the PCM ? thanks again

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 09, 2011

    darn. I'm not familiar with that immobilizer. Is there an indication on the dash panel? Are you using the factory key? If yes, is it a plain key or does it have something special on it? I will do some research.

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 09, 2011

    Also, which engine do you have?

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 09, 2011

    Here is a link on the immobilizer. This one is nasty. I will keep looking for an easy fix. http://www.2carpros.com/questions/jeep-o...

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 09, 2011

    Here is a fixya post. It says to lock and unlock both front doors with the key to disarm the system. Another guy here says to look in the owners manual. I believe this guy, but I couldn't find the manual online. http://www.fixya.com/cars/t1067268-canno...

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 09, 2011

    here is another one with slightly different answer. wonder who is right? http://www.fixya.com/cars/t7938517-left_...

  • Anonymous Feb 09, 2011

    Hi yes on the dash near the windscreen is a little box when the car is locked with the immobliser it has a small flashing red light , when disarmed it goes out . On the immobliser box it has a date 1997 could it be an after fit . the jeep is a 1996 cherokee limited could it be because its inported in to austrailia. Its a 4 L motor and the key is plain its got a kidney shaped immobliser hanging on it , its got 2 buttons on it i tried another hand peace but no luck. I will try the door locking tips thanks again.

  • Jeffrey Turcotte
    Jeffrey Turcotte Feb 09, 2011

    OK, if the door lock/unlock doesn't work, I think you will need a scanner to see why the immobilizer is activated. Maybe you can borrow a scanner.

  • Paul Nease
    Paul Nease Feb 23, 2011

    i found that i had the same problem it turn out to be the neutral safety switch. Common problem on the jeep Check out this web site it may helphttp://go.jeep-xj.info/howtoNSSrebuild.h...

  • ford_is_powe Jun 16, 2011

    I'm having the same problem w/ a '95 Grand Cherokee. It sends power to the coil & injectors when switched to RUN, but just for a couple seconds. While cranking, it intermittently pulses power, but never pulses ground. Fuel pressure is good. I replaced the crank sensor already on a whim. Has anybody found a fix?

  • Jeffrey Turcotte
    Jeffrey Turcotte Jun 16, 2011

    Hi, I recommend you check to make sure your crank sensor is getting power and the return signal is getting to the computer--basically check the continuity of the wires.
    If you suspect an immobilizer issue, check the Jeep forums for a way around it. There is a post here: http://www.cherokeeforum.com/f5/1998-gra...

    If none of this works, the PCM may be bad.

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