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Thread: 1997 Range Rover P38A (GEMS) - Strange Electrical Problem

  1. #1
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    1997 Range Rover P38A (GEMS) - Strange Electrical Problem

    Hi All,

    I am hoping someone has come across a similar issue I am currently having with my P38A, or perhaps point me in the right direction. I have an electronics background (board level repairs and design - so I can usually diy all repairs), and usually can find the faults easily, but I'm struggling with this issue, and from searching many of the forums I can't seem to find a similar group of symptoms. I've owned this car for 16 years, so I know it quite well, inside and out. I also have a Blackbox Faultmate (locked to this car's vin).

    The car starts and runs ok, EAS working, all instrument cluster gauges and warning lights working, but the headlights and parking lights are always on (and cluster backlights) - they turn off when the ignition is off, the switch makes no difference. The windscreen wipers will only work at full speed, and they stop wherever they are on the windscreen when turned off. The key will only unlock the front 2 doors (used to do all 4), and the SRS light is on when car started, then flashes dim/bright after about 30 seconds. The radio and hevac are all working, and so are indicators, brake lights, alarm sounder, windows etc....I cannot get into the becm or srs module with my faultmate...it throws up an error, but I can access EAS module OK.

    Battery is fully charged, I have so far checked the ground and 3 12v feeds to the becm......removed and checked all connections to the becm, from going through the electrical troubleshooting manual checked grounding points E181/E182, E252/E253/E254, and E154....all seem OK. Checked all fuses - OK, replaced under bonnet fuse box - no difference. I've opened up the BECM and checked the mosfets that switch the headlights lights (traced back from C120 and C113) but all are good.....no dry joints etc.

    I'm running out of ideas, I really cannot find a common connection to all the faults except the becm.....I suspect it's a becm issue, but hoping someone else might have some ideas?

    Any help greatly appreciated.

    Thanks.
    Bruce
    Last edited by bruceph; 9th June 2022 at 10:45 AM. Reason: more details

  2. #2
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    I've done a bit more testing, and still cannot find any common issue.....

    The headlight switch works when the ignition is in position 1 or 2, if I remove a bulb it detects a bulb failure....with ignition off I can turn parking lights on with switch, and shows correct message on the cluster....once engine started parking lights and headlights are on, no matter what but headlights will not go to high beam.

    Tailgate works fine, rear 2 doors will not unlock....only front 2 doors. Rear electric windows work ok, and display the not set message on the display....so they are getting comms ok. Horn works ok, mirrors work ok, windscreen washers work ok.

    I'm beginning to rethink a bad earth somewhere, maybe with the srs?

    I'll keep searching...

  3. #3
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    Quote Originally Posted by bruceph View Post
    Hi All,

    I am hoping someone has come across a similar issue I am currently having with my P38A, or perhaps point me in the right direction. I have an electronics background (board level repairs and design - so I can usually diy all repairs), and usually can find the faults easily, but I'm struggling with this issue, and from searching many of the forums I can't seem to find a similar group of symptoms. I've owned this car for 16 years, so I know it quite well, inside and out. I also have a Blackbox Faultmate (locked to this car's vin).

    The car starts and runs ok, EAS working, all instrument cluster gauges and warning lights working, but the headlights and parking lights are always on (and cluster backlights) - they turn off when the ignition is off, the switch makes no difference. The windscreen wipers will only work at full speed, and they stop wherever they are on the windscreen when turned off. The key will only unlock the front 2 doors (used to do all 4), and the SRS light is on when car started, then flashes dim/bright after about 30 seconds. The radio and hevac are all working, and so are indicators, brake lights, alarm sounder, windows etc....I cannot get into the becm or srs module with my faultmate...it throws up an error, but I can access EAS module OK.

    Battery is fully charged, I have so far checked the ground and 3 12v feeds to the becm......removed and checked all connections to the becm, from going through the electrical troubleshooting manual checked grounding points E181/E182, E252/E253/E254, and E154....all seem OK. Checked all fuses - OK, replaced under bonnet fuse box - no difference. I've opened up the BECM and checked the mosfets that switch the headlights lights (traced back from C120 and C113) but all are good.....no dry joints etc.

    I'm running out of ideas, I really cannot find a common connection to all the faults except the becm.....I suspect it's a becm issue, but hoping someone else might have some ideas?

    Any help greatly appreciated.

    Thanks.
    Bruce
    I would be trying to figure out why you cant talk to the BECM with the fault mate. With the L322 its a CAN bus, but I cant quite remember the P38, I think its just a twisted pair K-line type thing.

    There is a fellow in Sydney called LAB electronics who cracks opens BECMs and solders ~6 wires to the main board and then plugs that cable into his nanocom. It gets around the K-line/diagnostic harness issues. That might be a backup plan. I took mine to him and he fixed it all up in 30 mins and was fun to chat to too.
    Now: 2005 L322 Vogue 4.4 M62TU (Black)
    Before: 2000 P38A HSE 4.6 - stately capability | 2008 Kluger KX-S | 2004 Forester | 2000 Yamaha XJR1300 | 1993 VR Calais | 1974 HQ Statesman - 308 V8 | HT | HK

  4. #4
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    Yes,

    This seems a BECM issue to me. I have never had such faults in any case. A bad earth can cause quite a headache, I agree, but comms should work as long as ground and one of the 12V connections (can't recall which one) is hooked up. As a last ditch desperate measure you could disconnect power from the BECM and feed it a direct 13.8v from a power supply and see if you can then log in with the faultmate. Simple test that can rule out further searching around the car?

    Cheers,
    -P

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    Quote Originally Posted by glenhendry View Post
    There is a fellow in Sydney called LAB electronics who cracks opens BECMs and solders ~6 wires to the main board and then plugs that cable into his nanocom.
    Lee Bourgois at Labtronx in Mittagong.

    Labtronx Home
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    2003 L322 Range Rover Vogue 4.4 V8 Auto
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    Thanks guys for the advice. I'll try sorting out comms to the becm and then see where that takes me. I might order a secondhand becm from the UK just to be on the safe side also (then I can get LAB to reprogram)....I'll update as I progress in case it is of help to anyone in the future.

    Thanks,
    Bruce

  7. #7
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    How old is your fuse box?
    I had a few wierd electrical things going on with mine, I was able to get hold of a second hand fuse box, which I swapped over, and that one caused all sorts of issues, radio turning off and on, hevac turning off and on, central locking playing up, alarm going off, among other things.
    I got hold of a new correct fuse box for mine (2001 Bosch) and all the problems went away immediately.
    It has been fine ever since.
    Might be worth a shot

  8. #8
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    I don't know but I've had a few guys with Faultmates and other supposedly Land Rover scanners (mainly with the L322) have issues with reading the proper codes. Just pops up with some non generic code that you can't do anything with.

    I would recommend plugging in a good Bi-directional scanner and see it that makes more sense. It is OBDII after all.
    04 L322 Vogue V8 - Work truck
    07 Freelander 2 TD4 SE - The wifes
    74 Leyland P76 Targa Florio - Aspen Green
    91 Kawasaki GPZ900R


    Previous LRs = 78IIa series - 81, 93, 95 RRC - D2V8

  9. #9
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    Thanks again for the suggestions.....I have already replaced the under bonnet fuse box.....unfortunately it made no difference.
    The Faultmate is a dedicated P38 diagnostic system using "Vehicle Explorer" (https://blackbox-solutions.com/suppo...hicle-explorer).....it cost me around $1800 about 15 years ago....it's specially designed to provide full diagnostics as the P38's are not fully compliant (earlier) than the standards of OBDII from my reading and understanding.

    I appreciate your suggestions. I plan to rig the Becm up on the bench and see if I can communicate.....the Melb weather is making working on the car even more fun

    Cheers,
    Bruce

  10. #10
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    G’day mate,

    Sounds like a bugger of a thing you’re chasing. It would be nice if they just told you where to look! I have a faultmate and a nanocom. Personally, the nanocom is easier to use and follow through for diagnosis. It was also WAY cheaper than the faultmate.

    Rehardless, my 0.02, I used the nanocom to turn on my headlights. So now whenever I run the engine, the headlights are on (except when the park lights are selected on the dial). It’s easy to turn on and off.

    Last year I put water in the cab on the drivers side crossing one of the deep crossings in Cape York. In doing so, I damaged the BECM. I drove about another 100km before having the opportunity to lift the drivers seat to take a look. Lucky for me the engine ran fine still, I had no dash signals or lights whatsoever so I was driving blind. I cleaned up the water and dodgy wire joins, and the only remaining issue that I’ve got with the P38 is that the rear doors don’t lock or unlock with the keys. Otherwise it’s fine. What I’m leaning towards here is that I think the BECM is more robust than people give it credit for.

    In your case, unless you selected the option to run the headlights using the faultmate, I think your BECM is not a happy chappy, or there is an issue with the wiring somewhere in that path. Personally, I’m leaning to the latter as I believe the BECM is more robust that we give it credit for. Short of getting it wet, or a wire not quite home, I hope it’s an easy fix mate.

    Cheers
    Keithy

    2002 P38 Range Rover HSE

    Sequential LPG - Redarc Charger - TPMS - Ashcroft Locker
    Wheel Carrier - Bullbar & Spotlights - 285/75/16 BFG KM3’s
    On Board Solar - Stainless Snorkel - 2” Suspension Lift

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