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I have a mack ch600 1996 model . I have a light that comes on listing a electronic malfunction also a shut down light appears. They come on a while then go out may stay on all day or just a few seconds. I have noticed that the tac begins to jump and not hold steady at the rpm the engine is running. Soon as the lights go out the tac starts working like it should. This truck is a all mack running gear. I had it at mack but they have not been any help. They could not get the lights on while it was there. I do not know how to pull up a code myself. Can anyone help me track down my problem.

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i dont know if it works on the 96 but the 2000 model we have you turn your cruise control off and with the key on and a malfunction light on press and hold the set button on the cruise control when the light goes out let off it the light will begin to blink count the blinks then there will be a pause and it will blink again so it may blink 4 times then 2 thats a code 4-2 after that press the set again if and count if you get the same you have just that code if multiple codes just keep reading until you get to the original one.

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  • 3 weeks later...
  • 2 weeks later...

Only 3 things will cause an engine shut down light to come on-1) coolant temp, 2) coolant level, 3) oil pressure. The reason for the tach jumping around may be an engine position sensor issue. The sensor is located below the starter on the driver side of the flywheel housing. Measure the resistance of the sensor, it should be between 200-300 ohms. Also measure resistance from pin A and pin B to ground, it should be an open circuit-any continuity then replace the sensor. If all looks good so far then check sensor adjustment, turn the sensor all the way in until it contacts the flywheel then back the sensor out one full turn.

If you are still having issues then it could be an intermittent open circuit, short to ground/positive. Its hard to tell without knowing the fault FMI

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