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mcratchet1

Help with 9.2 code

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ok i have a 2006 mack mr688s (032711) with a concrete boom sitting on it. The truck would act like it was shut off but never cut out, the code is coming from vecu. It was happening once a month then once a week now 2X daily i checked from the batteries to power relays and everything in between and cannot find anything, the starter, alternator, engine grounds, frame grounds, the ground relay on drivers side by air filter behind little black cover its very annoying especially while pumping concrete any  other trouble shooting advice would me great thanks!!!

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Posted (edited)

If it has a night switch bypass it temporarily.

Edited by fjh

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yup

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actually i just replaced the key switch monday, problem seemed to go away until yesterday it dropped out while he was pumping

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Did you go completely through the 9-2 service bulletin point by point?

Are you Fleet, Private or Dealership?

Edited by Mack Technician

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yes, the only thing i do not have a pin tester to check relays, but the did have good scratches and fit tight

we are a small private pump company we have 7 mack trucks

I called mack for a diagram of the fuse and relay layout in the dog box but they said they cannot give me that info they are never helpful

032711 is the last 6 of vin do you have access to fuse and relay location?   

Thanks

 

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Sorry, don't have access...… Get 2 pizzas and a flat of printer paper and show up at the dealership during the nightshift. They can print out the whole thing for you off impact. Make your own diagram book.

If I owned the truck I'd be tempted to ease a few wires and grounds out of critical low amp control circuits and take control.   

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ok found high/low beam relay bad changed been running with no problems for a month now did same thing 2x today also this morning truck would not start. When i turned key only heard buzzing coming from these 4 relays. Does anybody know what these control? im guessing one has to be starter i cycle the key a few times then it cranks i checked to the wire had 11.50 but when i turned key switch dropped to 5.5 volts now truck will not start going to just start tracing wires unless someone could help a brother out 

Thanks!!!

IMG_8425 (1).jpg

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Posted (edited)

If they’re buzzing you have a short to ground on the power output of the relay(post 30’s output side).  If you have a 30 AMP relay they buzz if you try to draw more than 30 AMP through them. Protection feature. Those are more than 30 amp. Hard to read.

Edited by Mack Technician

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