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[drmryan]

Hi guys,

I went down to the local supermarket earlier for some shopping and when I got back to the car, it wouldn't start. It would run for about a second, so I clicked 'unlock' on the fob again which usually disables the immobiliser but it still wouldn't run for more than a second. After a few attempts at this, the dash lights went off and although it'd turn over it wouldn't fire. The immobilser light on the dash wouldn't go off.

I had to call the RAC in the end and he got it to work by holding the 'unlock' button for 15 seconds or so, locking it, unlocking it and the immobiliser switched off. He thinks maybe the fob got out of sequence but isn't certain. He also thought maybe it could be an electrical fault in the dashboard.

Can anyone advise what might have caused this issue? Is the RAC man right or should I be looking somewhere else? And was the method of resetting the immobiliser correct or did he somehow fluke it?

Car is a 98 ZJ Grand Cherokee.

TIA

Daz

[Cockney Boy]

Disconnecting the car battery for 30 seconds sometimes helps, but it seems that this is a common problem with the May and Schofield immibilizers

[eastryjeep]

A funny thing you should mention this problem today!
Just yesterday, while collecting a bit from Lighthouse and chatting away as one does there, the guys mentioned that one of their jeeps had died in a similar manner, they did all the usual carpark stunts of disconnecting the battery etc but it remained stubbornly dead. When they later connected it to the Chrysler diagnostic tool the ECU would not even communicate.
'Bu**er', I bet they thought, but just on the off chance that that BS could baffle brains they changed the CPS & lo and behold it all came back to life!
Now being the curious guys they are, they tested the old CPS and found that the 5v feed to the sensor had grounded out to earth, as opposed to just dying in the usual open circuit manner.
So they then played about a bit and found that the same thing will happen if any of the sensors fail this way.
I hope this is of help to somebody one day even if it does not solve your problem this time.
But a person could go through a mint of cash changing all kinds of expensive bits and pieces when a few continuity checks on the sensors can cure a fault that even confuses the OEM diagnostic tool.