[Newell 381]

1994 or 1995 Coach# 381, Series 60 DDEC III, Allison HT741

Hello all, last night my family and I were about 20 miles from home, and we hit a dip in the road (I knew it was there and slowed down to about 55mph). After passing thru the dip, the cruise control shut off, the low coolant light flashed, and the coach immediately began losing power, I thing the engine was actually shutting down, because a few seconds later, I lost power steering and was able to fight it to the shoulder of the freeway. Now long story short, we towed it home, pulling it with a heavy duty tow strap with my F-150.

Problem: Engine spins over but will not fire off, Trans Check (Amber) stays on, cant get it to flash codes when holding the Trans Check switch. I check the flash codes on the Engine ECM and got (Red Light) code 25 and (Amber Light) 54, 46, and 43. We have the coach home now so my family and it are out of danger, only now I cant move it without towing it. Any help is appreciated. I'am a Heavy diesel mechanic by education so I have a little bit of knowledge but this problem has me stumped.

[Fulltiming]

The code 43 should be low coolant. The code 46 should be battery voltage low. Code 54 should be speed sensor fault. Code 25 interestingly enough is no codes.

Since the faults seem to be tied to the passing through the dip, I would be checking the connections at the DDEC unit and the Transmission ECU.

[rheavn]

Check grounds.

[Newell 381]

I checked all the connections going into the Engine and Transmission ECMs, I sprayed them down with contact cleaner and re-inserted them. Took all the grounds loose I could find, wire brushed them down and re-attached them. Still no luck on getting the engine to start and the orange “Check Trans” light is still on.

[Fulltiming]

You may have to resolve the Transmission issue before the engine will start. If the transmission ecm wiring is OK, it should be able to be diagnosed.

[Yort]

Low voltage can cause odd things to happen. What is the condition of the batteries?

[dannymarilyn]

Remember if you have an Allison transmission, there is an interlock to prevent you from shutting the engine off until the transmission is in neutral. If somehow the engine was killed while the transmission was in gear, that might be a possible no start problem. At least that is how ours is wired.

Good luck!
Danny
1991 # 277 8V92 w/Allison transmission

[Richard]

You may want to flash the codes on the Allison to see what it’s ECM thinks is wrong.

[Newell 381]

I tried flashing the transmission codes but nothing happens. Is there a different procedure for the trans other than holding the switch down?

[Fulltiming]

Assuming you have an Allison MH 3000 transmission.

https://rvtechlibrary.com/transmissions/...rators.pdf

See starting page 60.

Per the Allison 3000_4000 Operators Manual:
Diagnostic Code Display Procedure
Pushbutton Shift Selector.
Bring vehicle to a stop at a safe location
Apply parking brake
To Display Stored Codes:
1. Simultaneously press the up and down arrow buttons once to access the Oil Level Display Mode - press the buttons a second time to access the Diagnostic Display Mode
2. Observe the digital display for codes.
- Diagnostic codes will appear one digit at a time on WTEC III pushbutton or lever shift selectors.
- Diagnostic codes will appear two characters at a time on Allison 4th Generation Controls pushbutton or lever shift selectors.
3. Press the MODE button to see the next code - repeat for subsequent codes.

Pages 65-72 lists Codes