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need help with OBD codes 700 1990

posted by  Joe Bonner on  Sat Jul 8 11:03 CST 2006
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last visit: Fri Jul 29 11:51 CST 2011
[RELATED]

I have a 1990 740 turbo wagon, recent work includes new clutch and clutch cylinder and replaced tranny (with used M46).

My wife had the car the other evening, and as she was accelerating to pass another car (highway speed), she noticed that the car was acting as if the transmission had dropped out of gear (although she was in OD and the OD light did not go out) and the check engine light came on.

She took it to a garage the next day to have it checked and the mechanic recommended that we replace the crank position sensor based on the following OBD codes:

2-1-4 crank shaft position sensor fault
1-3-1 ignition system RPM signal
2-3-1 Lambda sono not operating

Does this sound right? Based on what I have read in the FAQ, a faulty crank sensor is associated with a no start condition, which is not the case here.

FWIW, the mechanic cleared the light, and the same thing happened on her drive home.

Any insight would be appreciated.

Thanks.







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    need help with OBD codes 700 1990

    posted by  Chris Mullet on  Mon Jul 10 01:01 CST 2006
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    last visit: Fri Oct 24 09:08 CST 2014
    [RELATED]

    Any chance you bumped/damaged the CPS or its wiring while replacing the clutch?
    --
    Chris - 1990 740, 1973 1800ES (Non-running), 1993 Dodge Dakota (Still has a little paint left on it)








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    I'd consider replacing the CPS on GP. Reliability issue. 700 1990

    posted by  someone claiming to be JohnB on  Sun Jul 9 03:33 CST 2006 [RELATED]

    You're fortunate that the car is somewhat driveable. I'd make one more check...use the IDU to confirm the CPS signal...it's in the Bentley or maybe in the FAQ on how to do it.

    Otherwise it's possible the OD is simply slipping or kicking out of OD (check the lubricant level...I think the OD is separate from the manual trans oil. On automatics they use the same sump. The codes appear to be irrelevant to trans operation but that doesn't mean the codes aren't valid for CPS operation.

    The CPS tends to fail soft...usually difficulty with starting and then no start hard failure. CPS is relatively cheap to replace and you can do it yourself without a great deal of difficulty.








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    need help with OBD codes 700 1990

    posted by  interstition on  Sun Jul 9 02:15 CST 2006
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    last visit: Mon Apr 28 10:13 CST 2014
    [RELATED]

    By acting "as though it had dropped out of gear" do you mean the engine raced but the car kept slowing down? If so, I would think it is transmission related.

    A crank position sensor would usually cause a no-start and could cause the engine to cut out, but if the engine is running your CPS is working.
    --
    Andy in St. Paul - '91 745 213K mi, '91 745 210K, '90 744 183K, all Rex-Regina - past 240s








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      need help with OBD codes 700 1990

      posted by  Rule 308 on  Mon Jul 10 06:12 CST 2006
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      last visit: Tue May 8 09:20 CST 2012
      [RELATED]

      The oil in an M46 as well as an AW70 are common, that is to say that the overdrive units in both boxes use same lubricant as the trans that they are bolted to.

      The diagnostics on the CPS is such that it must see an interuption in the signal for it to log a code. So, if you go out to start your car and it does not start because there is NO signal from the CPS there will be no code stored. If you are rolling down the road and it gets interupted, signal goes away AND comes back, then it will log a code and turn on the CEL. The reason for this is that if it logged a code everytime the signal went away and did not come back then it would also log a code everytime someone stalled a car with a manual trans. This is the way it is explained in Volvo school anyhow. Being as you have a code in either side (A2, A6) then I would stuff an new engine speed sensor in it.

      Hope this makes sense and answers your question
      Mark







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