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peterpete190, Auto Technician
Category: RV
Satisfied Customers: 29093
Experience:  Over 17 years diagnosing and repairing various model vehicles.
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We have a 1992 Monaco Dynasty with an Allison MD 3060

Customer Question

We have a 1992 Monaco Dynasty with an Allison MD 3060 transmission, a mechanical 6CTA 8.3 Cummins motor and a Jacobs exhaust brake. Several months ago the exhaust brake became erratic and then not operating. I have done the following:
1. Checked the throttle switch to make sure it is functioning as well as the brake
2. Changed and added a spring per Cummins.
3. Changed all of the relays in the Vehicle Interface Module (VIM).
4. Cleaned all of the connectors to the Allison ECU.
5. Checked voltages at the ECU per John at Transmission Instruments.
6. Cleaned and reconnected all grounds in the dashboard and front run panel.
7. I had some codes on the key pad.
d1 = 3500, power interrupt
d2 = 3414, power interrupt, block check sum
d3 = 2112, Throttle Position Sensor (TPS) below low
d4 = --
d5 = --
8. The power interrupts were due to a cheap screw type switch on the ground side
of the chassis battery. (Since removed)
9. Took the MoHo to an Allison repair shop which is very thorough and
professional. They installed a new TPS and we went for a test drive with their computer connected. The brake worked perfectly. I started home and tried the exhaust brake, it didn’t work. As it was after hours I continued home.
10. Took the MoHo back a couple of days later and when their computer was
hooked up for another test drive THE BRAKE WORKED PERFECTLY. The service manager and the tech had not seen this before.
11. Removed, cleaned and checked the resistance of two speed sensors on the
12. The exhaust brake will work once in a while, not much, and only after about 10 seconds after I activate the switch on the dash.
Submitted: 2 years ago.
Category: RV
Expert:  peterpete190 replied 2 years ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

My info is somewhat limited on your model here but I had seen no one else has responded and would like to see if I can help here.If at any time you feel that I cannot help with this please let me know.

If you have not checked or had checked for any damaged wiring leading to the engine and transmission sensors this needs done.I find in allot of cases damaged or shorted wiring can cause this issue here and have seen this as a common fault on allot of the bigger model vehicles.If a fault is found it will need repaired.This will also cause this to be intermittent like this here.

If this was already checked and found to be o.k. let me know so we can continue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete.

Customer: replied 2 years ago.
The sensors at the transmission and the engine have checked out as good as well as the wiring. It's come down to, why there is a delay when the brake sometimes works and why does it work perfectly when a laptop with Allison software is connected to the data port at the bottom of the dashboard?
Expert:  peterpete190 replied 2 years ago.

Unfortunately this is all of the info I have here on this myself.I will open your question up for others here to see if someone else can assist further on this as there may be others here that may have more info on what to check or do with this issue.I hope you can get this resolved with ease.No need to reply to my last post here unless it is a last resort as it will keep your question locked to me and others will not be able to view it.If you feel you want to continue to work with me on this feel free to reply at any time but keep in mind in some cases it can be difficult to fully diagnose or help repair this without seeing your vehicle.

Thanks Pete