P0705/P0708 TRS errors, not TRS?

Lincoln Mark VIII

  1. Bangster

    Bangster Dedicated LVC Member

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    So I have been fighting with a couple of codes, and the dash not showing what gear I am in, inability to manually select second, and message center message of gear select err (and blinking OS light with check transmission in message center).

    2 codes I got are p0705 and p0708:
    P0705 - Transmission Range Sensor Circuit Malfunction (PRNDL input)
    P0708 - Transmission Range Sensor Circuit High Input

    I ordered a TRS/MLPS/Neutral Safety Switch (first one was wrong, for early cars), and replaced it (not without tearing up my hand, why is nothing easy?). Still have the same issue.

    All the pins seemed to be okay in the connector to the TRS, and I didn't see any issues with the other connectors (that are attached to the transmission crossmember). They were really greasy, I degreased the whole mount and blew it all out with compressed air, I didn't tear into the harness itself, the plastic bundle and everything is still intact. I did unhook the connectors from the cross member and pull them apart and clean then with contact cleaner.

    It wasn't the easiest thing I have ever done, I am sure most people here can R & R the entire transmission in the time it took me to get it hooked back up. I also found some very sharp metal and made my hand swell up like a balloon.

    Any other common failure points for this?

    24668644819_699cd5167b_b.jpg
     
  2. Bangster

    Bangster Dedicated LVC Member

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    FINALLY was able to dedicate enough time to solve this, instead of 10 minutes here and there. Searched a little more and found on the Mark VIII it is frequently the ECU that is bad, and found a TSB on it. 32 bucks for an ECU and still happened (thought maybe that is why car was in junk yard, it was otherwise pretty damage free).

    For the 10th time I pulled the wiring connectors apart, cleaned them with contact cleaner, and used some dielectric grease. This time I also completely degreased the wiring harness (unwrapped), connectors, transmission mount and crossmember, linkage, pan, case, (with purple lightning and a brush and a gloved hand, followed by rinsing and warning up, then foaming degreaser and a rinse), and so far in 4 trips with lots of manual shifting, it isn't failing anymore, no pending code(s), no blinking OD light, no gear selector error, and I can manually select Second gear (this is secondary to actually passing emissions, but it was a drivability concern).

    http://www.stangnet.com/images/stories/docs/sn95_TSBs/98-23-12.pdf
     
    Last edited: May 22, 2016
  3. Bangster

    Bangster Dedicated LVC Member

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    It doesn't set the CEL, but now I have a p0712 (which I can only get from my XCal-II, cheap bluetooth and wired elmscan don't read it), which I have had for most of the time owning the vehicle, even after replacing the TFT and cleaning up the harness and connectors. I know it isn't overheating as it happens at cold start. I guess I need to dig into the harness more, maybe try to get one from the junk yard while they still have a Mark VIII (as every other 4r70w car has the harness off the back the engine, down the transmission from the front, not through the body/tunnel at the back of the transmission).
    26998374320_414d66280b_b.jpg

    And my favorite code of all, I think this is the cause of my poor performance:
    27274168065_289fee1199_b.jpg

    For whatever reason I get 10-12 codes every time I take it in for emissions testing, even with the 97 ECU in (it has a 98 in it now), and it runs poorly until I let it cool off and do a cold start.
    26998385270_83643fc4b1_b.jpg
     

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