Tell me it is not my PCM
01-31-2018, 01:55 PM
#16
Senior Member
That test sounds good.
It should also disable the alarm when the two front door lock cylinders are unlocked w/ the key, also disable when the IR remote is used to unlock.
It might be the CCD bus failure causing the problem.
It should also disable the alarm when the two front door lock cylinders are unlocked w/ the key, also disable when the IR remote is used to unlock.
It might be the CCD bus failure causing the problem.
01-31-2018, 02:07 PM
#19
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Year: 1993
Model: Grand Cherokee(ZJ)
Engine: 5.2
well thats been the way it has been since i have owned the Jeep so it was low on the list of looking into.
Do you think it would be worth looking into disabling the alarm altogether?
Do you think it would be worth looking into disabling the alarm altogether?
01-31-2018, 02:16 PM
#20
Senior Member
The non-functional front door lock disable switches are not the source of the existing problem.
The FSM states that the PCM requires the VTA, unless a PCM for a non-VTA vehicle is used.
The availability of replacement PCM units is equivalent to that of hen's teeth, so fixing the problem is the best bet.
The FSM states that the PCM requires the VTA, unless a PCM for a non-VTA vehicle is used.
The availability of replacement PCM units is equivalent to that of hen's teeth, so fixing the problem is the best bet.
01-31-2018, 02:22 PM
#21
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Year: 1993
Model: Grand Cherokee(ZJ)
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what i assumed, thats why the locks are not high on the list of issues. Well guess i will start with the VTA check to see how it fairs.
01-31-2018, 03:58 PM
#23
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Year: 1993
Model: Grand Cherokee(ZJ)
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after reading all that it seems a bit hit and miss but it but also something to look into once i get it back started.
01-31-2018, 09:47 PM
#24
CF Veteran
I could be off here, but if the front door key switches. do they work? will they shut the alarm off? Seems he is saying the back hatch shuts it off.
01-31-2018, 10:22 PM
#25
Senior Member
The vehicle has a switch on each of the three exterior key cylinders, all with identical function, to disable the VTA. The OP vehicle has broken functionality on the two front doors, but normal functionality on the rear liftgate.
02-01-2018, 05:00 AM
#26
CF Veteran
Ah. So would it be possible if the door key cylinder switches are stuck in one position or the other, could that still be affecting the vta adversely despite the one rear hatch switch apparently working? After all the vehicle is 25 years old, no telling how many times those switches have been turned. The service dept at the stealer once told me they saw a "ton" of problems relating the the vta and those switches, most common failure they said.
02-01-2018, 06:06 AM
#27
Senior Member
The wiring diagram shows all three lock cylinder switches are wired in-parallel, providing a single input to the VTA.
If any switch failed in the active state (shorted to ground) then that would prevent the reported proper functionality of the liftgate switch.
02-01-2018, 08:25 AM
#28
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Year: 1993
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Ok so wingless you mentioned the CCD bus in an earlier comment, i have been looking through the manual and wondering if there is any common spots I need to hit 1st?
02-01-2018, 08:34 AM
#29
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My suggestion would be to run through the FSM tests first.
Those tests should ID bad front door key switches and hopefully nothing else.
The only tool required for the FSM tests is a multimeter.
Assuming those tests find no other problems, then a DRB II tool permits additional testing. Those tests would identify a CCD bus fault. Note that the Mopar DRB II tool becomes available on eBay at a reasonable cost. It permits examination of the three diagnostic connectors on the vehicle, one for the PCM, one for the ABS and one for the air bag.
Resolving a CCD fault would start w/ wiring tests and examination, per the FSM wiring diagram
Those tests should ID bad front door key switches and hopefully nothing else.
The only tool required for the FSM tests is a multimeter.
Assuming those tests find no other problems, then a DRB II tool permits additional testing. Those tests would identify a CCD bus fault. Note that the Mopar DRB II tool becomes available on eBay at a reasonable cost. It permits examination of the three diagnostic connectors on the vehicle, one for the PCM, one for the ABS and one for the air bag.
Resolving a CCD fault would start w/ wiring tests and examination, per the FSM wiring diagram
02-01-2018, 08:41 AM
#30
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Year: 1993
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OK sounds like my plans stays where it is for the moment then. I have to work tonight so i will run through it hopefully saturday and report back as to what I find! However being i know it sets off and disarms as i would expect (just via the doors) makes me wonder what i move to next after as i should be able to get through that check with plenty of time to spare.
One thing i have seen is unplugging the crank and cam sensor and possibly the 02 to see if the chk engine light activates then. Any insight on those or where would you head after if the VTA checks out ok?
One thing i have seen is unplugging the crank and cam sensor and possibly the 02 to see if the chk engine light activates then. Any insight on those or where would you head after if the VTA checks out ok?