goeclectic
New Member
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Hi, my beloved 1998 P38 4.0 V8 automatic RR has developed a bizarre interimittent fault that I cannot find discussed elsewhere - I have spent days searching forums and asking garages. So just in case someone out there has any idea what could be behind it or even better knows the magic incantation to fix it here goes.
After 30 or so minutes of driving in High Range, I stop at traffic lights and put it into P (still on the High Range side) and it will decide all by itself that it wants to be in Low Range instead of High. The flashing cog wheel shows on the dash and it tries to change. If I move the gear selector to Low range it completes successfully. If I don't move it, it complains about wanting to be in Neutral if I try to select a gear and it won't drive. After moving the Gear selector to low range, the yellow cog wheel stops flashing, the red low range side lights go on permanent and I can drive in low range. However all attempts to get it back into High range fail. If I try to put it back in High Range it will show the flashing lights (cog light on dash and flashing green lights on the gear selector High side) but never complete. Then if I leave it over night and start it up the next morning - it decides it will complete the change to High ratio and until the problem rears its ugly head again will happily change between High and Low range.
The usual culprits for Hi/Lo selection problems are the Hi/Lo range motor on the transfer gear box, the XYZ switch or the Transfer range ECU. But, the motor works, the XYZ switch works (its only influence on Hi/Low range changing is sensing neutral position which it does), the ECU works. But something is not working once everything is warmed up.........and something is making it decide that it wants to be in Low ratio all of its own when I try to put it into P or in fact change the position in any way.
Another possibility that I don't see mentioned anywhere is the Hi/Lo switch in the center console but I can't find any mention of where this is or how to check it? Anyone know where this is?
The only course of action appears to be to replace each component one by one and check all the wiring until it either stops misbehaving (ridiculously expensive - into right-off amounts, nightmare to test/validate as it only happens after its been used for half an hour or so) or I exceed my life expectancy...
If I have to go the route of swapping out components which one would you advise to start with ( the ECU?).
After 30 or so minutes of driving in High Range, I stop at traffic lights and put it into P (still on the High Range side) and it will decide all by itself that it wants to be in Low Range instead of High. The flashing cog wheel shows on the dash and it tries to change. If I move the gear selector to Low range it completes successfully. If I don't move it, it complains about wanting to be in Neutral if I try to select a gear and it won't drive. After moving the Gear selector to low range, the yellow cog wheel stops flashing, the red low range side lights go on permanent and I can drive in low range. However all attempts to get it back into High range fail. If I try to put it back in High Range it will show the flashing lights (cog light on dash and flashing green lights on the gear selector High side) but never complete. Then if I leave it over night and start it up the next morning - it decides it will complete the change to High ratio and until the problem rears its ugly head again will happily change between High and Low range.
The usual culprits for Hi/Lo selection problems are the Hi/Lo range motor on the transfer gear box, the XYZ switch or the Transfer range ECU. But, the motor works, the XYZ switch works (its only influence on Hi/Low range changing is sensing neutral position which it does), the ECU works. But something is not working once everything is warmed up.........and something is making it decide that it wants to be in Low ratio all of its own when I try to put it into P or in fact change the position in any way.
Another possibility that I don't see mentioned anywhere is the Hi/Lo switch in the center console but I can't find any mention of where this is or how to check it? Anyone know where this is?
The only course of action appears to be to replace each component one by one and check all the wiring until it either stops misbehaving (ridiculously expensive - into right-off amounts, nightmare to test/validate as it only happens after its been used for half an hour or so) or I exceed my life expectancy...
If I have to go the route of swapping out components which one would you advise to start with ( the ECU?).
