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Unread 07-10-2010, 03:04 PM   #1
Zolly
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1994 Jeep Grand Cherokee cranks but does not start..

1994 Jeep Grand Cherokee cranks but does not start..

My 1994 Jeep Grand Cherokee (ZJ) does not start up. About 30 seconds after turning on the ignition, the SECURITY light appears on the dashboard. Previously I charged the battery and forgot to remove one of the car’s clamps so the car was energized while charging. As another mistake, I forgot about it and I was cranking it during the charging process. The syndrome is exactly what I found in the VTSS section of the owner’s manual: ” If the Security Lamp comes on after ignition ON and stays on, the CCD bus communication with the PCM has been lost.”

I am glad that I found this hint about this specific fault, but I do not know how to go ahead (the explanation is not very clear for me). In my interpretation it might mean that the security alarm module cannot “see” the PCM and blocks the ignition (or the PCM is blocking it). CCD bus means for me that the PCM is maybe not energized (although fuses seem to be OK), so I tend to go into the following direction:
- checking whether the PCM is energized or not. How can it be done the best way?
- If the PCM is energized, then the communication is lost due to another reason. Unfortunately, the PCM connector is a 60-way connector, with many options to measure. What should I focus on?
- Is it possible that any of the sensors is ruined? (crankshaft position sensor & CAM position sensor, engine coolant temperature sensor, intake manifold air temperature, manifold absolute pressure sensor and throttle position sensor) If so, how can I find it out? Which one is wrong most likely?
- If the PCM is faulty and has to be replaced, how can I find it out? I do not want to buy a new PCM just to find out later that it was not needed at all.

It is clear that the charger ruined something, but I do not know whether it is the PCM itself or something else.

Any help would be greatly appreciated!

Thanks in advance,
Zolly

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Unread 07-11-2010, 02:40 AM   #2
SouthZJ
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1995 ZJ 
 
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if the Security module causes the shut down the engine would start and the cut out

you can deactivate the security module with grounding the purple wire in the door i think it was passenger side, just use the search function here in the forum t should pop out

if it is the Crank or cam sensor you would have a code for it when doing the key trick

To display codes cycle the ingition key On-Off-On-Off-On within three seconds. Count the number of flashes, first digit, pause then second digit will be displayed in a series of flashes. (2 flashes, pause, 1 flash = 21)

11 - No Crank Reference Signal At PCM (Crankshaft Position Sensor)
12 - Battery Disconnected Within last 50 Key-on cycles
13 - No Change In MAP Sensor
14 - MAP Voltage Too Low Or Too High
15 - No Vehicle Speed Sensor Signal
17 - Engine Is Cold Too Long
21 - O2 Sensor Signal At Center Or Signal Shorted To Voltage
22 - ECT Sensor Voltage Too Low Or Too High (ECT = Engine Coolant Sensor)
23 - Charge Air Temperature Sensor Voltage Too High Or Low (Intake Air Temp Sensor)
24 - Throttle Position Sensor Voltage Too High Or Too Low
25 - Idle Air Control Motor Circuit Shorted
27 - Injector Control Circuit Signal Not Responding Correctly.
31 - EVAP Purge Solenoid Circuit Open Or Shorted
32 - EGR System Failure
33 - A/C Clutch Relay Circuit Open Or Shorted
34 - Speed Control Solenoid Ciruit Open Or Shorted (Vacuum Or Vent)
37 - Torque Converter Clutch Solenoid Circuit Open Or Shorted
41 - Generator Field Not Switching Properly
42 - Auto Shutdown Relay Control Circuit Open Or Shorted Or No ASD Voltage
44 - Battery Temp Sensor Voltage Out Of Limit
45 - Overdrive Solenoid Circuit Open Or Shorted
46 - Charging System Voltage Too High
47 - Charging SYstem Voltage Too Low
51 - O2 Sensor Signal Stays Below Center (Lean)
52 - O2 Sensor Signal Stays Above Center (Rich)
53 - Internal PCM Failure
54 - Sync Pick-Up Signal Not Detected (Camshaft Position Sensor/Ignition Pickup)
62 - PCM Failure SRI Miles Not Stored
63 - PCM Failure EEProm Write Denied

55 End Of Codes (thats always there)
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Unread 07-11-2010, 05:50 AM   #3
Zolly
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Thanks for your reply. My car is at the mechanic right now so I can do the DTC test and get the trouble code(s) only tomorrow. I will provide you with a feedback on the outcome.

The engine does no start at all, so it is likely that the shut down is caused by other than the security module.

Assuming that the fault is associated with one of the sensors or the PCM, should we do the diagnostic measurements while the ignition is ON?

If the CPM works and only a sensor or connection is faulty, is it possible to somehow jump/bypass this ignition blocking feature, or the starter solenoid? I’d need to get the jeep started at least to drive it to another mechanic. The current mechanic seems to be overdone with the green beast, and is rather unwilling to continue the diagnosis, by saying it is too difficult for him.

Is it correct that the 94 ZJ is only OBD1 compliant and has its diagnostic connector somewhere under the hood? Do you eventually know where exactly and how it looks like? Would it have any additional advantage to attach a scan tool? (e.g. reprogramming or for any other purpose)
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Unread 07-11-2010, 04:48 PM   #4
SouthZJ
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Quote:
Originally Posted by Zolly View Post
Thanks for your reply. My car is at the mechanic right now so I can do the DTC test and get the trouble code(s) only tomorrow. I will provide you with a feedback on the outcome.

The engine does no start at all, so it is likely that the shut down is caused by other than the security module.

Assuming that the fault is associated with one of the sensors or the PCM, should we do the diagnostic measurements while the ignition is ON?

If the CPM works and only a sensor or connection is faulty, is it possible to somehow jump/bypass this ignition blocking feature, or the starter solenoid? I’d need to get the jeep started at least to drive it to another mechanic. The current mechanic seems to be overdone with the green beast, and is rather unwilling to continue the diagnosis, by saying it is too difficult for him.

Is it correct that the 94 ZJ is only OBD1 compliant and has its diagnostic connector somewhere under the hood? Do you eventually know where exactly and how it looks like? Would it have any additional advantage to attach a scan tool? (e.g. reprogramming or for any other purpose)
the 94 ZJ juust have OBD 1 thats right so you dont get much info there,
Do you have a repair manual for you ZJ?

There thy explain how to check every sensor and will also tell you where the OBD plug in thing sits

just to make thinks more clear when you turn the key to the on position the lights on the dash come on and if you turn it to the start position does the engine crank over and dont start or nothing happens in the start position?
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Unread 07-11-2010, 11:53 PM   #5
Zolly
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Thank you for your reply. Yes, I have just downloaded the service repair manual for ZJ (93-98). I see how the sensors can be checked. There are many sensors (up to 6-7 or so) relating to the ignition/PCM, should we check all of them?

As to your question: yes exactly as you wrote: when I turn the key to the on position the lights on the dash come on and disappear after a short while, and if I turn the key to the start position the engine cranks over. Subsequently, the security lamp comes on and remains on. Today I go to the mechanic and check the trouble codes through the self-test.
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Unread 07-12-2010, 12:12 AM   #6
SouthZJ
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Quote:
Originally Posted by Zolly View Post
Thank you for your reply. Yes, I have just downloaded the service repair manual for ZJ (93-98). I see how the sensors can be checked. There are many sensors (up to 6-7 or so) relating to the ignition/PCM, should we check all of them?

As to your question: yes exactly as you wrote: when I turn the key to the on position the lights on the dash come on and disappear after a short while, and if I turn the key to the start position the engine cranks over. Subsequently, the security lamp comes on and remains on. Today I go to the mechanic and check the trouble codes through the self-test.
first check the Crank and the Cam sensor they both trigger the cut off but also ground the purple wirer in the door that will disables the security system i am just not sure in witch door it is
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Unread 07-12-2010, 03:35 AM   #7
cmpnaz
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Try taking your key and double check the security is disarmed by putting it in your lift gate and lock then unlock the gate and try starting it again.... if it is disarmed start try your meter and check the crankshaft position sensor 9 times out of ten it will be one of the two
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Unread 07-12-2010, 07:42 AM   #8
Zolly
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SouthZJ,
Thanks for your reply and continued support. I am just back from the car mechanic with some potentially important news. I was trying to carry out the ON-OFF-ON-OFF-ON self-diagnostic test to get some trouble codes but it was not possible. The check engine lamp did not come on (as I have just noticed), there were no flashes to count. Even more important, the check engine light does not appear for a short while when turning on the ignition. Seemingly, the regular engine test does not take place (or the check engine bulb could be blown out, but it would not explain that the engine does not start).

My mechanic checked the PCM’s 60-way connector’s battery supply (cavity 3), and it is available (energized), the grounds are also OK (11, 12). We have checked the security alarm module’s CCD connections, but no current flows to the PCM module. That seems to reaffirm the service manual’s description that the CCD bus connection has been lost. On the other hand, the security module seems to work.

What is the fact indicating that the check engine lamp does not come on? Is it the failure of the PCM, or a sensor, or the security alarm module is faulty? I assume that the check engine lamp should work if any of the sensors is faulty, so guess that the PCM is faulty most likely, but how can I prove or test it? (Check engine light does not appear even if the SAM is disconnected.)

How should we go ahead? Should I check the Crank and the Cam sensors anyway? (I cannot even do the self test as you originally suggested due to the lack of check engine light flashes).
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Unread 07-12-2010, 08:05 AM   #9
Zolly
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Cmpnaz,
Thanks for your advice. The security system is disarmed for sure. I cycled my key in the driver’s door, passenger’s door and also in the lift gate. Actually, I tried both of my keys several times. I also tried to cycle it 3-6 times but to no avail. We even disconnected the security module. When my mechanic reconnected it, the ignition was not possible, the engine did not crank until I cycled my key on the door once. Subsequently the cranking worked but the engine did not start as before.

One of the error indications is that the security lamp comes on 30 seconds after ignition is turned into the on position. It is described in the service manual: ” If the Security Lamp comes on after ignition ON and stays on, the CCD bus communication with the PCM has been lost.” My mechanic has just checked the security alarm module’s CCD connections, but no current flows to the PCM module. I don’t know whether any current should be here or since it is unavailable, whether it is due to the PCM’s fault or the security module’s fault. Or it might be eventually normal that no CCD current is available between PCM and SAM if the PCM is not working, which might be eventually the case.

The other error indication is that the check engine lamp does not appear for 1-2 seconds after turning the ignition to the on position. By counting the flashes of the check engine lamp in diagnostic mode I would get some trouble code for a sensor or module, but due to the lack of the check engine light I cannot do the test either.

Should we go ahead and check the crankshaft position sensor even if the check engine light is absent? What do you mean by checking the crankshaft position sensor “9 times out of ten”? What should happen 9 times and what on one occasion out of ten?

What does in your view the lack of check engine light indicate?

Last edited by Zolly; 07-12-2010 at 08:15 AM..
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Unread 07-13-2010, 02:13 AM   #10
cmpnaz
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Sorry i think you misunderstood the 9 times out of ten.... It has been my experience that 9 times out of ten when you have a problem as you describe it was one of the two issues... I have seen mechanics not realize the security feature and after battery disconnect not being able to start until they were told to disarm using the lift gate ( in 94 ZJ it can be disarmed with remote or in the lift gate) .... the other times and a couple out in the middle of some trails I have seen guys stuck because the crankshaft sensor failed. The CSS failing is not always going to trip the check engine light. The engine will not operate if the pcm is not receive input from the CSS. check your book on how to test with your ohmmeter and make sure it has infinite resistance ... if it is low metering low resistance replace it
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Unread 07-13-2010, 03:08 AM   #11
Zolly
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Thanks a lot for clarifying the issue in details, and I’ve also got your message regarding the 9 times out of 10 expression. In the meanwhile I found out the following. The service manual states that if the PCM receives an incorrect signal or no signal from certain sensors or emission related systems the yellow check engine light lamp is turned on (pin 32 of PCM). In my case this lamp does not turn on at all, indicating the possible fault of the PCM. On the other hand, I read in the repair manual that the red security lamp staying on means that the CCD bus communication has been lost with the PCM. (CCD might mean Chrysler Collision Detection). Since all the indications imply the CPM’s fault, we will first check the CPM and if it is unclear whether it is faulty, I will acquire a replacement part. I agree that the engine will not operate if the PCM does not receive input from the crankshaft sensor. But it seems that the PCM does not work correctly either. The next step would be to test CSS. As you correctly described, the CSS failing could trip the check engine light, but the check engine light (connected to the PCM) does not operate at all in may case.
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Unread 07-26-2010, 01:31 AM   #12
Zolly
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Dear Contributors,

Finally, the case has been solved. Due to your supportive feedback the assumption has been confirmed that the PCM was faulty. Fortunately, I found an electrical mechanic who could spot and repair the problem, so actually there was no need to buy a new PCM. It was a tiny IC in the PCM that busted. The most unambiguous indication pointing to the PCM’s fault was that the self-diagnostic test (ignition on-off-on-off-on) could not be carried out because the check engine light did not flash, and the yellow engine symbol did not appear either.

Again, thank you very much for your invaluable support which made it possible to narrow down and solve the problem efficiently! I wish you all the best.
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Unread 01-14-2011, 05:23 PM   #13
bummed
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power to coil wire somtimes
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Unread 03-18-2011, 05:24 AM   #14
bobkat2
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I just came across this thread and I'm having the same issues exactly. I did try another PCM with no avail but maybe it was bad as well. I have no yellow check engine light coming on on the dash. I will check the internals of the PCM and check for anything obvious.

Thanks for your effort and the information you've provided
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Unread 10-13-2011, 09:46 AM   #15
ace811
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Hi Sir Zolly,

Can you identify the IC replaced by your electrician in the PCM. I am having very similar issue with my 94 Cherokee XJ.

Thanks and regards,
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