JoeH

2-3 intake air sensor 4-1 vehicle speed sensor (you have trans codes, so this will likely be linked to whatever is going on there) 1-4 ambient air temp sensor To verify EECU power, there's a bolt holding the wiring harness to the engine lock below the EECU. Takes a 10mm socket. Remove that to create enough slack to undo the 2 plugs into the EECU. They're pretty odd how they unlatch, the end the wires come into needs to lift waaay out once you undo the retainer lever. On the bottom plug, pins 10, 22, and 41 should have 12v power sourced from one of the 4 big relays hanging next to the VECU in the dash. You are probably fine on power to those terminals, I see you have a CB in the #40 slot now.

Sounds like you are moving in the right direction. Loose circuit breaker connections can be squeezed to firm them up. There's a "patch" repair to backfeed clean power into the EECU. Without looking at your truck in person I can't know for sure if your EECU is actually getting power. I didn't see a breaker in CB-40, which should be the power to three 12v power pins on the EECU plugs. Truck can crank but won't start if the EECU doesn't get power. If I read correctly, you're working with one battery. It will take 2-3 batteries to start this thing. If the voltage to the EECU drops to 7 (going off memory) the EECU will power off until the voltage normalizes. The draw on one battery trying to start this thing is significant. Trans codes can be pulled as follows: press up/down arrows together, hold for a few seconds. Display will say "d1" then a 4 digit code. Press Mode to move to next 4 digit code. I believe it has 4 code slots? Each one listed as "d1", "d2" etc. Once you get to "dX -" you are to the end of the active code faults. These are Allison codes, so you will have to sift through Allison data to find what they mean.

1999 and 2000 had the engine ECU under the turbo. 2001 saw the switch to driver side, which was a good move. I don't know enough to know if the diagrams would match or not. But his truck is 1 year newer than mine so hopefully they're close enough! Mines an ai350 to his ai300. Same trans!

You seem to be hitting the wall I climbed 2 weeks ago!

Here is the schematic for the Clean Power. You should see the numbers 343A 2.0 and 336A 2.0 on the wires in the plug in the grille I'm referring to.

I made the mistake of deleting these during our frame job because I assumed they were for the trash body. You may have done similar, or someone else did prior. If you don't know which plug in the grille I'm talking about I can get a picture tomorrow.

Also on the trans keypad there should be a 20 amp fuse and + and - wires that run from a battery to a plug in the radiator grill. These wires supply "clean power" (power that is has no voltage fluctuations from other systems sharing power feed) directly from the battery. Clean power comes through that 20a fuse then should go straight to fuse #65 which is 10a.

I don't think there's a VMAC4? Correct me if I'm wrong? Yours should be a VMAC III.

All the way towards the driver seat in the row "above" those three breakers.

You don't even have #40 installed. It should be a 25 amp Mini fuse or breaker.

You should be able to figure out Who is Who from these pictures.

https://www.diesellaptops.com/products/diesel-explorer Also download this onto a laptop while it's still free, and when you can stomach the cost buy their $683 Diesel Link Adapter so you can plug into the truck. You can see if all the computers are powering up and communicating. For us, it wasn't listing the Engine ECU, which ultimately was because it wasn't powering up due to fuse connectors for #40 were loose.

I had same issue on mine, fuse #40 was loose. # says CB-40 (Circuit Breaker)

Quality worse than I expected.

Here's the diagram for the 2003 we have been working on. Bergeys had to put in a service request directly to Mack to get this diagram for me. Top rate dealer! Look at fuse #40, check that the fuse is in there good and tight. Also you need to run Blink Code Diagnostics. Key On Engine Off (you can run it with engine running but you aren't there yet), hold the cruise control button (I forget which one) down til the Lightning Bolt goes out. It will then blink out a 2 digit code. Count the flashes. When that code is done the light will come back on and stay on. Press cruise again to display next trouble code. Repeat until it continues to display numbers it's already put out. Tell us what the codes are, so we can look them up for you. Also buy yourself Mack Manual 8-211, that's the VMAC III diagnostics book. It's a must have!

There is one thing it CANT be: Cheap!

This truck is a breeze to work on. First time we have had a transmission out and back in in one day. Old seal spun in the flywheel housing. We could move it by hand. New seal has Bearing Mount Loctite, and is recessed 1/4 inch per spec in our handy shop manual. Thanks Mark! Only frustration is this thing was supposed to be in Iowa yesterday. This snow storm coming in across the Midwest to new england later this week means the truck won't be in Iowa til Monday or Tuesday, barring any other roadblocks.

Was supposed to leave yesterday, but Illinois apparently doesn't sell trip permits, so we have to reroute an additional 500 miles to go around it, and we found a rear main seal leak so we have to pull the trans off today to replace seal.

Dumb question, you aren't driving around with the PTO on right?

Yea. Mack trucks only draw from one tank. Usually passenger side. Crossover line allows fuel between the 2 tanks to self level. I drove a Peterbilt (Poorlybuilt) that had a switch.... You could suck from one tank and return to the other? Seemed kind of dumb to me. But what do I know?

"If I do not have an IFTA license and have a qualified motor vehicle traveling interstate what do I need to do?" OUr truck doesn't "qualify" it's PA only. Need a trip permit to "qualify"

Need to drive our 03 Mack MR688 from PA to Iowa. JJ Keller can sell me a trip/fuel permit for every state but Illinois. WTF? Does Illinois sell trip permits? Our truck/DOT # is set up for "Intrastate only" in Pennsylvania. Is there any legal way to drive through Illinois or do we have to detour through Kentucky and Missouri to get to Iowa?

Curious, how much did the harness set you back? We just bought a 2003 AI350. Harness seems ok... For now....

Hell, Mack should add the wiring harness to the filter tune up kit! "Change your wiring harness with every oil change!" Make your truck run like new again!