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2000 Mack RD688s Electronic Malfunction Light Stays on with ignition off

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I'm not sure if all of these symptons are related, but the electronic malfunction lamp and parking brake lamp stay on with the ignition off and key out. Retrieved a trouble code of 6-4 from Electronic Malfunction lamp. Recieved a touble code of 7-3 from the ABS Light. Truck starts/runs/drives normal. Any insight would be much appreciated!!

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The elec. malfunction light in my RD has been coming on every day also, but the truck runs fine. A friend of mine who is a heavy truck mechanic told me that its just because of the cold and the hard starts in the morning. It does go off after about two hours of driving. sorry not much help.

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The 6-4 fault is j1939 serial data line. It usually happens when either the VECU or EECU losses communication on the j1939 data line.

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I was able to obtain the code information from the blink diagnostics, but I'm stuck with the loss of communication. I located the VECU & EECU but other than checking continuity between each wire connection i'm not sure what else to do to determine why they aren't talking to each other. Any thoughts?

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Is the shutdown engine light also lit? All the way on the left side of the dash by volt and oil pressure gauges.

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no shut down lights doesn't come on. ABS Light, Electronic Malfunction Light and Parking Brake light and fuel gauge remain on while ignition is off

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I would check your ignition switch. The fuel gauge being powered up shouldnt go through either ecm or vecu. It should not be powered up with the key off. Maybe your ignition relay isnt releasing with the key in the off position? Your parkbrake and check engine light should come on and stay on when you turn your key to on with the engine not running.ABS light i'm not sure of. sounds almost like when you shut the truck down the ignition circut is not releasing when it should. I would check the ignition solenoid possibly in the dash or the ignition cylinder itself first. going to need to trace power starting at the key when the key is in the off position.

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