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’97 XJ Grand Cherokee, Anti-theft system, no power / ground to Injectors

304 Views 2 Replies 2 Participants Last post by  Huntlyr
Expert advice please! ’97 XJ Grand Cherokee, Anti-theft system, no power / ground to Injectors

Hi from sunny South Africa. I hope there is someone on here who has expert knowledge of the ECU and Anti-theft system on this model. (SA Export model)

Background - Overnight the XJ developed a no-start condition. No guages. Fuel pump running continuously. Diagnosed as defective ECU. Installed new ‘donor’ ECU. Guages working, ASD and fuel pump relay’s now prime correctly. On first 3 cranks engine fires, but dies after 1-2 seconds. After 3 attempts did not fire at all.

Diagnosis - The engine fires briefly when ‘Engine Start’ sprayed into inlet manifold, so problem diagnosed as as a fuel supply / injectors problem. Tested voltage to injectors and circuits. No/low power to injectors and no grounding by ECU. No error codes though.

Expert advice received - after 3 attempts to crank using incorrect keys (i.e. that do not match the VIN number stored in the ECU / SKIM module) the anti-theft system immobilises the vehicle by disabling the ECUs injector control circuit.

So, I then had the correct (original) VIN coded into donor ECU so that it matches the original keys and SKIM. The anti-theft warning lights go out when vehicle is opened with original key / FOB, but still no fire or start. Further advice received was that the anti-theft system will only reset the ‘disabled injector status’ after the key has left in the ‘on’ position for over 2 hours.

I performed this procedure, but engine still does not fire (although it does when ‘Engine Start’ is sprayed into inlet manifold).

Can someone please advise 1) if the above advice and remedies are factually correct 2) if there are other procedures needed to reset the injectors’ control circuits 3) any suggestions on how to get the injectors operating again. Thanks!

(PS. I am now completely bald as I have pulled out all my hair over this issue and would really like to get this car going again!)
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several thoughts.
you say a GRAND CHEROKEE - a grand cherokee is a ZJ.
You also say a XJ - XJ is the Cherokee.
I'm thinking its a ZJ. yes ?

Codes - how are you checking codes? you need a SCANNER, and you can have codes and the CEL remains OFF.

Checking power 12v to injectors - if the jeep does not start in @2 seconds. the PCM will open ASD.... NO POWER to injectors.

Tell us is there a need to use the key fob to start jeep, AND is there a small red light on dash related to starting?
WHY - jeeps sold overseas depending on where had an additional immobilizer installed involving the key fob and the light was a clue.

I am attaching oem manual for theft snd security section , hoping it helps, let us know if you are still having issues...


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Thanks Jtec. I stand corrected... ZJ.

Thanks for the info on the VTSS and Immobiliser systems.

I think SA export models had the VTSS and the immobiliser as there is a SKIM key sensor at the steering column.
  • I can open the car with FOB or keys. Red anti-theft light flashes slowly when armed, and goes out when car opened.
  • No codes via instrument panel, but guy that coded the VIN said no codes via his Scanner.

What I really need to find out for sure is:
1. Whether the immobiliser system would or could have cut power to the injector circuits when I tried to start it after fitting a donor PCM (i.e. due to the mismatch between VIN recorded in the PCM and the SKIM module? OR

2. Whether the immobiliser system needs to be re-enabled as indicated in the info you sent me. Maybe it works by resetting the start counter to 0 or under 20?

3. Whether there is some other procedure to re-enable the injector circuits in the PCM after coding the correct VIN into the PCM. The immobiliser itself seems to be functioning correctly, but it may be necessary to re-enable by advancing the start counter happens when new vehicles are delivered or new PCMs are fitted.

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