Key Transponder Module

I am chasing down a ‘no cranking fault’ on my 97 XK8 using the Pinpoint Instructions in the Module Communications Network Section 418-00 of the shop manual. The first instruction is to disconnect connector FC22 from the KTM.

I would like to know, please, how to access the KTM. Its location is shown in the Electrical Guide as forward of and possibly above the Body Processor Module which I have removed but I can’t see the KTM anywhere. Can someone tell me how to get at it? This is a RHD vehicle.

Eric
Shropshire, UK

Are you reading a P1260 DTC???
That is the ‘code’ for security input engine disabled.

The 1997 XK in the North American market does not have this feature. I guess you had this earlier.
1998 was the first year for KTM and immobilizer here in NA. Read the DTCs to ensure that the fault is actually a security issue and not an electrical issue.

If no P1260, then look elsewhere for a start fault.

bob

Hi Bob,

Yes, I have a P1260 code which returns immediately it is cleared. There is reference to this in the shop manual where it says that unless the originating fault has been rectified the code will be re-flagged with 3 to 4 seconds. This seems to be happening.

There is something wrong in the immobiliser system but as you know, several modules are involved. I’m trying to be logical in my approach but the symptoms are confusing. If I re-sync the ECM & BPM and then re-programme the keys the car will start up each time, maybe for a few days, maybe only once or twice. Then it won’t crank. Once it won’t crank it will not start unless there is some intervention from me.

I discovered that if I did a hard reset it would start once but not a second time until another hard reset. Very occasionally it will crank but not start which seemed to me to point to the ECM because that controls ignition and fuelling whereas the BPM signals the start relay to operate. I changed the ECM but it made no difference to the fault.

To grab the low hanging fruits I tried a brand new fully charged battery and also I changed the exciter ring in the ignition barrel. Neither made any difference.

So I’m now trying to methodically work through the system for supply volts and grounds and checking the interconnecting cables as some of them have splices.

I’ve now got stuck because although I have a rough idea of the location of the KTM, I can’t see it or even its connector. There is no reference to replacing it that I could find either in the shop manual or JTIS so any help in what needs to be removed to get at it would be very much appreciated.

Eric

Have you tried another KEY??? (please don’t say you only have one)

I have seen a car ‘forget’ a key and the others worked OK. Maybe the key transponder in the key itself is faulty??

The electrical guide will have all the modules and locations. The FRONT MATTERS section of the guide will show where the modules are generally located.

bob

Yes, I had thought of the possibility of a crook key. I have three keys. All can be programmed and all will start the car until the fault occurs, then none of them will.

I was using the EG for the location of the KTM. It’s one thing to read where the guide says it is; it’s quite another thing to find it! It says the KTM is adjacent to the passenger side fusebox but the back of that fusebox is very difficult to see.

Next time I get to work on this car I’m going to pull out some more of the trim around the LH A post and see what’s there.

Eric

Hmm. Hello Bob and Eric…

Did this end up being the key, the KTM, the exciter? All? None?

Will an exciter from a donor car along with its key and barrel solve the problem of a no start due to the key fault? Does each exciter send its own unique message to key transponders to activate the KTM and push the appropriate signal up the line?

What would work in the combination, does every link in the chain need to be programmed, so they are all singing the same song?

I have power at the starter on both low and high voltage pins at the relay, but the control side of the relay doesn’t seem to be getting the ground signal from the BCP/ECU/M (sorry but I don’t know which controls the grounding at the starter relay) on key turn. It’s painful.

All ears here.

No, it was an SLCM problem. See my reply to your other question.

The ground that comes from the BPM to crank the starter is the very last thing that happens if everything else in the chain is OK. The BPM does need to be paired to the ECM and you do this using IDS or WDS or something third party that is capable of programming the modules. If they are the ones that were in the car before it got flooded they should not need to be reprogrammed. Neither should the keys. If you have to re-programme the keys or the fobs, you have to start by erasing them all.

Understood… I’ll be digging in tomorrow. Looks like rain, but what the hell, lol