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Thread: VT intermittent computer problem?

  1. #1
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    Default VT intermittent computer problem?

    My VT is developing an increasingly severe set of intermittent computer problems.

    E.g., when driving along, the Engine light, ABS light, Trac light, airbag light, and oil indicator will come on. A series of musical beeps sounds. Sometimes the temperature needle goes to zero. The signals will usually reset themselves after a few minutes. If I start the car and use the hidden trip-meter functions, I see that the fuel rate goes to 0.0 and the engine temperature to -40C when the problem occurs.

    The car can also be hard to start.

    I'm seeing diagnostic codes 12, 31, 48, and 92, which decode to

    12 Engine Speed Detection No RPM Input
    (Normal when Engine is Not Running)

    31 Theft Deterrent System: No Signal
    (Anti-theft communication between PCM and BCM)

    48 Camshaft Position Sensor No Signal (Received by PCM)
    Sensor Fault, Wiring or Connector

    92 Low Speed Fan No Response from BCM
    BCM Module, Wiring or Connector

    It is sounding like some sort of intermittent connector/wiring problem between the PCM (is that the computer near the passenger's left foot?) and the BCM (the Body Control Module above the driver's right foot). I've wiggled every connector that I can get my hands to, including all the ones on the PCM, with no improvement.

    Any help greatly appreciated.

    I bought the CD manual for the car (it cost me about $250) but I've misplaced the darn CD!

    Thanks,
    Michael (alias "frustrated")

  2. #2
    accentstencil's Avatar
    accentstencil is online now Donating Member
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    I don't know for sure but from a lot of earlier posts I've read when all those symptoms occur the problem has been the ABS module.

  3. #3
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    Thanks for the information. I have found my CD manual, and it is suggesting that the serial data connection between the PCM (Powertrain Control Module) and the BCM (Body Control Module) might be to blame. This can cause faults 31 and 92. I've checked the wire, and it is making good contact, and is not shorted to ground. Of course, being an intermittent fault, you never know where you stand!

    I hadn't thought the ABS module could be involved, but come to think of it, I do occasionally have the ABS and Trac lights coming on after starting the car. They stay on until the next restart. I reported this at one of the warranty services, but nothing was done to fix it.

  4. #4
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    Hm... I removed the ABS fuse, thinking this would disable the possibly faulty ABS module, but the fault still occurs. I'll have to check the circuit diagram, but this makes me think that the ABS module is not the one causing the problem. Perhaps another module is at fault, e.g., the instrument module or the airbag module?

    Another thing I noticed in the manual is that the ABS module is susceptible to interference from, e.g., the spark plug leads. Now, in my car the spark plug leads on the driver side were flapping in the breeze due to the long-ago failure of the little plastic thing that held them to the engine. So I tied them down carefully in the right position. I guess this is irrelevant if the ABS module is OK.

    Still frustrated.

  5. #5
    Doctor Bob's Avatar
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    unplugging the fuse will not isolate the problem, the failure causes the serial data circuit to ground dropping the entire data bus out, try unplugging the abs module & see how you go then.
    the codes you have
    12 normal should always be there when the engine isnt running.
    32 your remote key has failed at some stage
    48 more than likely a poor connection either at the cam sensor or the crank angle sensor or the dfi.
    92 generally means the low fan relay is faulty, not critical but there is an updated type available
    Rob

  6. #6
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    Just found exact same fault on my VT Acclaim today. Have not worked much on this car other than wiring my stereo in. Where is the ABS plug? Pulled fuse link under bonnet but with no change. Have bat volts to pos of fuse but zero to neg (fuse ok). Any ideas would be appreciated.

  7. #7
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    Thanks Dr Bob for those helpful remarks! I have pulled the ABS plug and am now waiting to see if the fault reoccurs. I wonder if the ABS module is repairable, or is it epoxied shut? I've already thoroughly cleaned contacts and looked for external shorts.

    Actually, another question: the manual says you can't replace the ABS module without disconnecting the brake lines, since certain spring plates have to be horizontal during reassembly in order to align them properly. I wonder if this is really true? If so, it requires bleeding the brakes I think. If not, a lot of effort is saved.

    steelebish - the ABS plug is a large rectangular black plug that connects to the ABS electronics module at the back of the ABS "hydraulic modulator" (the shiny metal thing with hydraulic lines coming out of it - nearish to the brake fuild container in the engine bay - there is a photo of it on a thread here somewhere). To pull the plug out you have to grasp a handle underneath the cable going to the plug, and pull it out by 30mm or so. The act of pulling the handle out moves the plug up. After removing the plug, ensure it doesn't get entangled with the fanbelt when you start the engine!

    Regards, Michael

  8. #8
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    ' I wonder if the ABS module is repairable, or is it epoxied shut? I've already thoroughly cleaned contacts and looked for external shorts.'

    Yes. I had a quote of about $300+ postage from AFI in Granville, Sydney. exchange basis.

    'Actually, another question: the manual says you can't replace the ABS module without disconnecting the brake lines, since certain spring plates have to be horizontal during reassembly in order to align them properly. I wonder if this is really true? If so, it requires bleeding the brakes I think. If not, a lot of effort is saved.'

    There are 6 screws that connect the module to the abs body. I had a used one put in by the local Holden dealership & for the time & cost involved, they definitely didn't remove the whole abs assembly & bleed brakes etc.

  9. #9
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    Cheers, I did find it when I used my brain and thought about it.

    My fault has not come back since leaving the plug disconnected. However I find if I tap the module lightly under the plug I can hear the relay pull in and the fault disappears.
    I have asked a couple of mates that are mechanics if you can remove the module at least to have a look and see if the relay I can hear needs replacing, they all seem to think that you may have to reset/program it after pulling it apart. Any Ideas.
    I don't like the idea of pulling things apart willy nilly that involve a safety feature.

    With the plug disconnected at least the A/C still works, just a pity the cruse control does not work.

    Has anyone inquired on a second hand one from a wreckers? I was thinking about calling one Monday.

  10. #10
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    There are a couple on ebay for V8s, I don't know if they are different for a V6 but you could ask them.
    http://search.ebay.com.au/search/sea...ule&category0=

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