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Old 03-25-2015, 08:02 PM   #15
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Originally Posted by lanerd View Post
So exactly what is the difference between an OBD connector and a J1939 Diagnostic Plug for ECM communications besides physical characteristics?

This is from a long time ago so if I am wrong sorry.

I believe diesels use a communication system similar (if not the same) as computer network. things like shifters, gas pedals communicate on the network and when you plug into a j1939 plug your device joins the network and can see the communication between ECM and device.

ODB2 is more like, the reader probes the ECM with predetermined codes like "Hey is there a O2 sensor 1" the ECM responds "Yes" reader then asks "What is the value of O2 Sensor 1" ECM responds "2.2"

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Old 03-25-2015, 08:20 PM   #16
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Actually, the OBDII plug reads serial data stream from the engine also. It is a 16 pin plug. Large diesels use the 6 or 9 pin plug with a different protocol. They both read the data stream and decipher codes and data. Unfortunately with a large Diesel engine you can't always get a scan tool to read the information and may have to go to CAT, Cummins or a Detroit Diesel shop to read the information or purchase a scangauge tool.

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Old 03-25-2015, 08:31 PM   #17
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Old 03-27-2015, 12:14 AM   #18
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I have a ScanGauge D on my rig. Easy to install, plug and play. Gives me tons of info on all the systems. I can clear trouble codes on the fly if need be. Well worth the money, check EBay. Back to the OP. You may have a bad ground to the gauge panel. Possibly loose or corrosion.

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Old 03-27-2015, 04:54 AM   #19
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Originally Posted by ramblerrob View Post
Yellow warning light on. The light came on while driving with the generator on. All of the dash controls fluctuated wildly and then the light came on. I now believe that I have a bad relay between the coach and chassis battery. However I would like to turn the warning light off, because I don't believe that it was a true warning.
I can't speak to your year model but MH's with a BIRD circuit have a generator lockout that should prevent both battery banks from combining if the engine AND the generator are both running. Mine can throw a fault if I hold down the aux start button under those conditions because it bypasses the BIRD circuit.

If you just want to clear the fault, try turning off or disconnecting both battery banks.

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