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Thread: check engine light does not work

  1. #1
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    check engine light does not work

    Hi,

    I think this is the right forum. I have a 2003 Saab 9-3 Linear (sports sedan) and the check engine light does not work. I've taken the cluster apart, and tested the led (it's good). I can plug in a scanner to the obd2 port under the dash and check for codes, but I'd like to get my light working. Electrically, this car is a nightmare. I had to rewire/replace the radio with aftermarket equipment because the radio would come on randomly and kill the battery. Also the remote start/alarm was ridiculous.

    I know this car uses a CAN bus (11-bit/500kb, I think- not sure what that means), but I have no idea where to go from here. I don't care if the led in the instrument cluster works as long as I can wire a light/led to come on whenever there is code in the system.

    I'm good with wiring, but not with programming. Whenever I try and read about data bus systems/programming I just get confused. Can someone point me in the right direction please, or direct me to someone who can even sell me a solution? I just want my check engine light to work.

    thanks

  2. #2
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    The "check engine light" is PCM controlled.

    Either the PCM went funky or your wiring did.

    You already established the LED works and you can see codes "tripped (?)"

  3. #3
    FLAC SNOtwistR's Avatar
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    Maybe its not a light tripable code. Some are next service issue (technically if you go back to dealer for service) Just a thought SNO

  4. #4
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    The reason I know it's an issue is because it failed inspection once. There was a code stored but no light. The light will not come on when the key is first turned like the others in the cluster either. I had desoldered one side of the led and tested it with the meter on diode check to verify it works. The only way I have of knowing if there is an issue is to plug in a scanner once in a while.

    Heavymetals, I'm sure the problem is with the pcm (the light is controlled by the CAN bus inside the cluster).

    SNO, I've actually done some testing to ensure the light should have been on- I unplugged the MAF sensor and started the engine (and still no light).

    This is why I'd like some sort of interface to warn me if there's an issue (like a check engine light)- even if I have to bypass factory wiring, etc. I just have no idea how to do so since the signal is over a data bus, and the solution is not just a simple wire tap. I don't mind paying someone to design/build a solution for me. Thanks for all the input- keep it coming.

  5. #5
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    Quote Originally Posted by SNOtwistR View Post
    Maybe its not a light tripable code. Some are next service issue (technically if you go back to dealer for service) Just a thought SNO
    I thought he said he put an OBD scanner to get codes so I assume it was check engine light related and that was his problem.

    If not, generate a known code.

    Disconnect a spark plug wire and that should be enough.

  6. #6
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    Quote Originally Posted by geepherder View Post
    The reason I know it's an issue is because it failed inspection once. There was a code stored but no light. The light will not come on when the key is first turned like the others in the cluster either. I had desoldered one side of the led and tested it with the meter on diode check to verify it works. The only way I have of knowing if there is an issue is to plug in a scanner once in a while.

    Heavymetals, I'm sure the problem is with the pcm (the light is controlled by the CAN bus inside the cluster).

    SNO, I've actually done some testing to ensure the light should have been on- I unplugged the MAF sensor and started the engine (and still no light).

    This is why I'd like some sort of interface to warn me if there's an issue (like a check engine light)- even if I have to bypass factory wiring, etc. I just have no idea how to do so since the signal is over a data bus, and the solution is not just a simple wire tap. I don't mind paying someone to design/build a solution for me. Thanks for all the input- keep it coming.
    The only way I know is to monitor the OBD continually with a code scanner.

    They are pretty cheap, but I would look into a spare PCM as they are pretty cheap also.

    http://www.ebay.com/itm/03-04-05-06-...3bd63d&vxp=mtr
    Last edited by heavymetals; 08-27-2013 at 04:50 PM.

  7. #7
    FLAC SNOtwistR's Avatar
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    When you unplugged the maf and plugged back in did you scan the obd2 port to see if it gave you a maf code? The reason I ask is you may not given it enough time to trip, also did you clear the old codes out and they came back or never cleared? SNO

  8. #8
    Constant Bitrate Rickk's Avatar
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    Some codes won't set a light.

    If you have a check engine light on, the light wont tell you what code. Only a reader will tell you what the code is, and only a reader will clear it.

    A reader is a good investment if you want to avoid giving tons of money to someone else. I got one for $100 bucks that does ODB2 and also ABS.

    Also, sometimes it is really hard to intentionally set a code. If they set too easily, customers would be complaining all the time. I had one bad coil in my 2000 F350. I could feel it missing severely but it wouldn't set a code. The only way I was able to diagnose it was to plug in a reader and disconnect coils one at a time until I found the one coil that had no effect on the fuel trim readings.

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