Check Engine Light, No Codes

Discussion in 'General Motoring' started by JRE, May 5, 2007.

  1. JRE

    JRE Guest

    OK, this is a puzzler.

    The CEL is on in my 1995 850 (non-turbo). It comes on about 5 seconds
    after the car is started and remains on. There are NO codes. The only
    blink code is the "I'm OK and there are no other codes" code. My OBD
    scanner shows no codes or pending codes. Pretty sure it's not the gas
    cap, FWIW.

    I've seen lots of odd automotive things, but never a CEL with no codes!

    Any ideas?

    JRE, May 5, 2007
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  2. The CEL is just a powered bulb grounded through the PCM. While there
    are DTC's which will not show up on a generic code reader or in the
    blink sequence, they are pretty much limited to internal PCM logic
    issues. Your Volvo dealer can extract them if you're curious. More
    likely you have a ground fault somewhere in the dash circuits.
    pathayes81946, May 6, 2007
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  3. JRE

    JRE Guest

    This turned out to be a transmission code. No clue why my scanner and
    the blink codes wouldn't show it, since it's a generic OBDII code.
    P0715, transmission speed sensor. The code's reset for now and I'll
    plan to do the resistance check this weekend.
    JRE, May 8, 2007
  4. JRE

    Glenn Klein Guest

    The reason is that the OBD2 reader just reads the engine control module
    so as in your case the DTC was set in the transmission control module as
    the other poster stated the dealer is able to read out all systems in
    the car with the Volvo System Tester (VST) this is made to read all systems
    Glenn Klein, May 9, 2007
  5. I have a similar issue on my 1995 850, the CEL light is stuck on and
    my code reader doesn't show any code consistently. Occasionally I get
    a P0755 to come out (something about a transmission selenoid) but then
    it goes away.

    Let me know what you find.

    Mark from Geneva, May 14, 2007
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