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Check Engine Light 700 90

The check engine light just came on in my 90 740 (159k). I had heard thru the board that loose fuel cap can cause this. I checked the cap-it's on correctly. Any other easy possibilities? Thanks!








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    Re: Check Engine Light 700 90

    The first thing to do when you get a Check Engine light is to retrieve the trouble codes from the computers and post your findings here. Lots of people have the factory manuals and will be able to tell you what they mean.

    If you don't know how to pull the codes let us know and we'll tell you how.








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      Re: Check Engine Light 700 90

      Brian,

      Thanks for your response. No, I do not know how to retrieve the trouble codes from the ECU. Any help would be appreciated!








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        Re: Check Engine Light 700 90

        There is a small (about 1"x2") black plastic box under the hood called the DLC (Data Link Connector), located on the driver's side fenderwall, between the strut and the firewall. That is where it is on my 240, yours should be similar.

        The top of the box lifts up to reveal 6 small holes (sockets), two of which have a female electrical connector inside (should be marked #2 and #6), a pushbutton and a red LED. Connector #2 is for the LH-Jetronic computer, and #6 is for the EZ-116 ignition computer. Each computer stores its own set of trouble codes, so you have to follow this procedure to read the codes out for each computer separately.

        /*********************************************************************/

        There should also be a small wire, the end of which is stored in a pocket inside the lid. Remove that wire from the pocket and place it in socket #2.

        Turn the ignition on. The LED on the DLC should not be on, or at the most it may be very dim. If it is on brightly the computer is probably hopelessly lost.

        Press the pushbutton for at least 1 second but less than 3. Note that the LED should illuminate when the button is pressed. This initiates the trouble code display sequence.

        All trouble codes are a combination of three numbers. A couple of seconds after the display was initiated with the pushbutton, the computer will reply by flashing the LED in three groups of pulses. For example, the "I'm okay" code is "1-1-1", and a missing signal detected by the ignition computer is "1-4-4". So, to show a "1-4-4" code, the computer would flash the LED once, pause a second, flash the LED four times, pause again, and flash the LED four more times for the last digit.

        If more than one trouble code is stored, the sequence will repeat itself until all the stored fault codes have been displayed. Note that you will always read at least one code, even if it is the "I'm okay" 1-1-1.

        Turn the ignition off.

        /*********************************************************************/

        Repeat the same procedure with the wire in socket #6. Don't be afraid to try the procedure a few times until you are comfortable with it. It might take a few tries at first to interpret the display.

        Tell us what you get and we'll tell you what they mean.

        Then we'll tell you how to delete the codes from the computer(s)!









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          Re: Check Engine Light 700 90

          Brian,

          The trouble codes are as follows: Socket #2 is 221, Socket #6 is 111.









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            Re: Check Engine Light 700 90

            Bob,

            I don't have my manual in from of me at this moment, but the 700 FAQ (at http://brickboard.com/FAQ/700-900/Engine-Codes1.shtml) has this to say about an LH 2-2-1:

            -----------------------------------------------------

            Fault Condition:

            Fuel trim (lambda control) too lean at part load

            Causes of Fault:

            Lean; air leak; low fuel pressure; bad AMM

            Symtoms:

            Engine stops when starting from cold; high fuel use

            -----------------------------------------------------

            It's not much, but it gives you a start. I can check my manual tonight and let you know what else it has to say.

            Cheers.








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    Re: Check Engine Light 700 90

    I wish it was so simple. There are lots of things that can cause that check engine to come on. I've been there and spent the money .

    good luck







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