UD Medium Duty No Power Check Engine Lamp On

Michael Mobile Technician Clinton, Utah Posted   Latest   Edited  
Case Study
Driveability
Network Communications
2007 UD 2600 7.7L (8 J08E-TE)
U0073 — Control Module Communication Bus "A" Off

Over the weekend I was asked to look at a UD tow truck. The driver stated that the truck lacked power on the highway and was sluggish in the city. I connected the TEXA tool to the truck and read the trouble codes. The code presented was U0073. diag​.​net/file/f128znr19…

The generic code stating that CAN channel A is offline could send you down a rabbit hole. The proper definition states that there is a lack of communication between the VGT (Turbocharger Control Module) and the Engine ECU. I found this in a document about the 8JOE engine. 

service-engine​.​com​.​ua/webroot/pdf/HI…​.​pdf

It was also convenient there was a diagram showing the controller and how it connects to the Engine ECU. I was able to disconnect the VGT controller. I checked for power, ground and CAN Hi / Lo. Both CAN signals were there with a nice square wave. The other connectors had battery voltage and ground. After reconnecting I tried to move VGT with bi-directional controls. There was no response. I condemned the VGT controller.

-Mike 

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Rex Technical Support Specialist
Alliance, Ohio
Rex Default
 

Your thoughts on the TEXA tool? Down the road I am looking at one. Mainly for the Hino's UD's ISUZU's.

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Ron, I was one of the first adopters of the TEXA tool several years ago. I became a dealer when I learned that the same pass-through device was used for anything from a motorcycle to Class 8 Truck. They have come a long way since then. Back in the day I had to take the salesman's walk of shame often when doing an on-site demo. Nowadays that does not happen too often. I personally know the…

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Michael Diagnostician
Champaign, Illinois
Michael Default
 

Hi Mike did you notice what the can was doing on the scope when you had the Vgt plugged in? Did you scope the power and ground and have current of the actuator as well?

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Hey Michael, That would have been some good follow through. My thought was that if it had a clean signal to the module, power and ground the module was toast. I have had several of these UD trucks with bad controllers. There is always a chance for high resistance in a wire. We don't have near the wiring issues here that you see in the rust belt.

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