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  #25  
Old 12-31-2012, 07:10 PM
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Re: Immobiliser Problem?

Well, its sat in the drive for months now so I really must try and do something with this. I did a bit of research tonight and found this: Jeep Chrysler Dodge Fix List

Two points this raises, Firstly it contradicts itself by initially stating the PCI bus pulse voltage is 7.5V but later saying that it should be 2.5V. Typo maybe? but which is correct? I was seeing 7.5V on the bus on mine but the text suggests that this is too much. Does anyone know what the bus voltage should be?

Secondly, the text refers to disconnecting each module on the PCI bus to locate the fault but doesn't say anything about the common junction box where all the bus cables join. Having got the dash in pieces on mine and not finding any such junction I'm beginning to wonder if it does actually exist. Has anyone on here actually located this junction?
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  #26  
Old 01-01-2013, 11:14 AM
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Re: Immobiliser Problem?

Happy new year to you, thought you had solved this problem, since no updates.
I'm sure the 7.5 V is too high, the 2.5 V should be ok.
There is a previous thread where one of the members is telling about the PCI disconnect point, maybe you can find it using the search function.
If you can't find it, you could disconnect each component and check if the bus voltage returns to the 2.5V.
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  #27  
Old 01-01-2013, 11:40 AM
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Re: Immobiliser Problem?

Quote:
Originally Posted by Frango100 View Post
Happy new year to you, thought you had solved this problem, since no updates.
Unfortunately not. Luckily I don't actually need the car although it would be nice to be able to use it if I wanted too!!

I took a bit of time to study the workshop manual last night (sad way to spend new year!) and discovered that surprisingly the bus voltage should be 7.5V. It also goes into detail about termination resistor values (although they have typo'd ohms into kilowatts). The more I read the more I believe that the bus is being corrupted by a faulty module on it. As I have already tried replacement PCM, SKIM and PDC modules I think I can rule them out. I have also tried disconnecting the looms into all of the doors so that would rule them out too. That really only leaves the transmission control module, ABS controller, A/C controller, Instrument panel, air bag and overhead console. My money would be on either the ABS or TCM as they are both under the bonnet and are both likely to be the most expensive to replace!!

If the weather is reasonable I may have another go at it at the weekend.
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Old 01-01-2013, 11:49 AM
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Re: Immobiliser Problem?

So then disconnect them one at a time and see if you can start the engine then.
Still strange that the bus voltage should be 7.5 V, i had red that this is too high.
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  #29  
Old 01-01-2013, 12:37 PM
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Re: Immobiliser Problem?

It surprised me too, but here it is straight from the manual - section 8e Page 8:

The modules bias the bus when transmitting a message. The PCI bus uses low and high voltage levels to generate signals. Low voltage is around zero volts and the high voltage is about seven and onehalf volts.

There is a lot of useful information in section 8 and it makes very interesting reading.

To be honest, I won't even need to crank the engine to determine whether the bus has data on it. If I leave my code reader connected to the diagnostic port as soon as data is present it will tell me. I suspect that the instruments will also burst back into life as well.
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Old 01-04-2013, 07:29 PM
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Re: Immobiliser Problem?

Just found some info on where the diagnostic junction port should be, just right under and at the end of the steering column.
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File Type: png 2010-09-15_025944_DJP.png (121.5 KB, 9 views)
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  #31  
Old 01-05-2013, 10:40 PM
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Re: Immobiliser Problem?

Thankfully I don't have much experience with your problem, but my only observation is since your fan turns on with the ignition on possibly it is your A/C controller. Most times when the A/C is selected it will automatically activate the fan as well. Best of luck I hope you have it running soon.
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Old 01-06-2013, 05:23 AM
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Re: Immobiliser Problem?

Frango100: Thats brilliant, I'll have a poke around in there with a work light later today (when the fog lifts!) and see if I can see it.

AMSOIL Dealer: Thats a very good point, as I have most of the interior in pieces getting to the A/C panel should be pretty easy.
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  #33  
Old 01-06-2013, 08:04 AM
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Re: Immobiliser Problem?

Quote:
Originally Posted by AMSOIL_Dealer View Post
Thankfully I don't have much experience with your problem, but my only observation is since your fan turns on with the ignition on possibly it is your A/C controller. Most times when the A/C is selected it will automatically activate the fan as well. Best of luck I hope you have it running soon.
Eventhough i wouldn´t completely rule out the AC head unit, its the PCM which commands the cooling fan on. The cooling fan on signal from the AC system side, comes from the AC pressure transducer directly to the PCM.
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  #34  
Old 01-06-2013, 01:12 PM
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Re: Immobiliser Problem?

Had a poke around under the steering column today and found this wrapped up in the loom



Looking at it more closely the cap over the end is effectively a bridge connecting all of the bus cables together



Obviously disconnecting this isolates all of the nodes on the bus so will prove nothing. Next step will be to build a connection block that enables me to switch out each node on the bus individually. I'm hoping that somewhere in the manual there is a pin out diagram of this connector that tells me which pin goes to which node. I'll be having a bit of a study tonight. If I can figure it out I'll remove everything from the bus except the PCM and see if it will communicate in isolation. If it won't I'll try the other PCM that I have. If this also doesn't work I'll have to start looking for cable damage inside the loom.
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Old 01-06-2013, 02:09 PM
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Re: Immobiliser Problem?

Surprisingly it was quite easy to decipher which nodes are connected to which pins from the wiring diagram. For reference they are as follows:

Pin 1
Sentry Key Imobiliser Module
CD Changer
Passenger Door Module
Transmission Control Module
Powertrain Control Module

Pin 2
Vehicle Information Centre
Seat Module
Drivers Door Module
Antilock Brake Controller

Pin 3
Automatic Zone Controller (a/c)

Pin 4
Radio

Pin 5
Airbag Control Module

Pin 6
Instrument Cluster

Pin 7
Not Connected

Pin 8
Body Control Module

Pin 9
Diagnostic Port

Pin 10

Not Connected

First thing to do then is to make up a jump lead to connect pin 1 to pin 9 and see if there is any data at the port. If not, then start disconnecting the nodes on that branch of the bus.
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Old 01-06-2013, 04:41 PM
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Re: Immobiliser Problem?

From which page in the manual did you decipher this? Could not find any info on this connector sofar. Strange that they connect TCM and PCM together, thought that all components could be separated via this connector. The stealer probably has a special connector to connect there and read each channel separately.
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