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Thread: 06 LR3 transmission in failsafe and alternator gremlin

  1. #1

    Default 06 LR3 transmission in failsafe and alternator gremlin

    I have my Girlfriends LR3 acting up. I have been a mechanic for many years but always steered clear of European vehicles (I always considered them as low longevity quality) so I know nothing about this thing.
    She parked in the garage and the next morning when she was leaving she backed out and when she placed it in drive the transmission made a long pause and then went into fail safe mode. I was checking the codes and it has “improper gear ratio (p0731). I watched the data stream and when it is shifted into drive the gear shown on the data switches from 3rd to 2nd sometimes to 1st bounces between 2nd and 3rd and finally stays in 3rd and bumps into gear all the while the data shows gear selected as 1st. I watched the solenoid amps data and the 1st solenoid has a slow (2 to 3 seconds) increase in amps while it is deciding which gear to engage. If I start driving and get up over 30 mph I can clear the trans code and the tranny performs normally until the speed drops to where it needs to drop into 1st gear then it free spins for a few seconds and drops back into failsafe.

    Also I noticed while checking it the alternator is acting odd. While letting the engine idle the alternator was registering 13.8 volts after several seconds of idling the alternator stops charging, the light on the dash illuminates and the voltage drops to 13.2 If I slightly rev the engine the alternator re energizes and goes back to 13.8. I have never seen an alternator de energize and re energize like this.

    My first question is.....is there a module that controls both these systems and second any idea how I can diagnose what is causing this issue?

  2. #2
    Join Date
    Oct 2011
    Location
    Mountains of Western Pennsy.
    Posts
    539

    Default

    If you don't have full voltage 100% of the time the computers (yes, there's more than one) will go nuts, and do all sorts of things and throw codes. Alternator and/or battery would be the first things to check (bad wiring in the charging system would be next). You pretty much answered your own question, when you're up to speed everything seems OK.

    '99 Disco II
    '95 R.R.C. Lwb (Gone...)
    '76 Series III Hybrid 109
    '70 Rover 3500S (Gone...)

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