Data Link Troubleshooting

[Naatv1]

2006 Monaco Signature Castle IV ISX600

Hoping someone here can point me in the right direction on my 2006 Monaco Signature that is having some sort of Data Link Issues.

I will try and explain what is going on to the best of my knowledge and see if anyone can help me. The other day I replaced both fuel filters opened up my Rear Run Box switched the switch to rear and started up the coach. Everything checked out fine so I cleaned up my mess and switched the rear start switch back to front. I then went up to the drivers cockpit and started the engine, at this point is when I noticed multiple issues. As soon as I started the coach I noticed that almost all of the gauges except the fuel level gauge and the air pressure gauges continue to "sweep" back and forth indefinitely. I also noticed a Check Engine Light, Check Transmission Light, ABS light, and my transmission shift pad is illuminated with 2 x's. I noticed that the speedo gauge is reading ECU Comm Err and Trans Comm Err. My Vorad is saying fault, also i noticed that there is no warning buzzer while the air pressure is building up to 50psi. Engine seems to start and run fine but I all my dash cluster is a mess.

Now through some diagnostics I found my rear run PCB had a diode that was missing and a ton of corrosion. I have since replaced the board and it has not solved any of my issues.

Through more diag thanks to some IRV2 members I have found an issue with my Data Link voltage values. I am getting an incorrect value when measuring values between A and C (.8v) as well as A and D (.7v) out of the diag connector. These numbers should be A and C (2.6v) A and D (2.3v) Now when I disconnect my engine ECU that is mounted on the side of the engine the values go back to where they belong. This makes me assume that the engine ECU is faulty, agree?

If the engine ECU is faulty can I order a used one from a junkyard/ebay/etc and plug it in as long as the P/N matches? My P/N 3684009

Any insight on this matter would be greatly appreciated.

Branden

[jacwjames]

Did you try cycling the Front/Rear remote switch a couple times?



I had a similar issue in that my rig wouldn't start and found that I had not seated the switch hard enough. After going through trouble shooting steps a couple times I cycled the switch making sure it was pushed completely in to the front and it solved my problem.

[Naatv1]

Originally Posted by jacwjames

Did you try cycling the Front/Rear remote switch a couple times?



I had a similar issue in that my rig wouldn't start and found that I had not seated the switch hard enough. After going through trouble shooting steps a couple times I cycled the switch making sure it was pushed completely in to the front and it solved my problem.

Yeah Ive tried that multiple times as well as replaced that board

[Wtbuck12]

Following.

[hypoxia]

Since you seem comfortable removing the ECU, I recommend you take it to Cummins or any shop with Cummins Insite to copy the program. NO one including Cummins has any idea of the programming that the now defunct Monaco put in it. It is a serious issue as it includes rear axle ratios, how the speed is transmitted etc. I have a Chinese Insite knockoff copy and you might consider getting one. With Cummins Insite you can see everything a Cummins tech can as well as copying your ECM program to a file. https://www.ebay.com/itm/Cummins-INL...IAAOSwIJlZ9U~7

[Naatv1]

Originally Posted by hypoxia

Since you seem comfortable removing the ECU, I recommend you take it to Cummins or any shop with Cummins Insite to copy the program. NO one including Cummins has any idea of the programming that the now defunct Monaco put in it. It is a serious issue as it includes rear axle ratios, how the speed is transmitted etc. I have a Chinese Insite knockoff copy and you might consider getting one. With Cummins Insite you can see everything a Cummins tech can as well as copying your ECM program to a file. https://www.ebay.com/itm/Cummins-INL...IAAOSwIJlZ9U~7

Thanks for the link, and yes very comfortable with removing the ECU. I have been an auto tech for over 15 years, the over the road diesel stuff is a little foreign to me but I'm having to learn it quickly.

If i buy a good used ECU off of say eBay etc, can I have the important info removed from my current ECU and transferred to the "new" used ECU? Or if there is a better option, Im all ears.

Thank you

[slemnah]

I think before condemning the ecm you should find a wiring diagram and see what else is on that data line. You may have another module taking it down. I would find all the modules and disconnect the:m to see if your voltages go back up.

[Naatv1]

Originally Posted by slemnah

I think before condemning the ecm you should find a wiring diagram and see what else is on that data line. You may have another module taking it down. I would find all the modules and disconnect the:m to see if your voltages go back up.

I can try that as well, should be pretty straight forward by unplugging the TCM, ABS, and VORAD modules. If unplugging them doesn't raise the voltage then I can focus on ECM again, correct?

[moisheh]

Data link pronlems can be a nightmare. Start eith cleaning all battery vonnrctions. Posts and connectors should be shiney? Find all the chassis ground connections and clean them. Are your batteries healthy. There are a bunch of Deutsch connectors for the J1939 comdata system. Sometimes a loose or corroded pin in those connectors can cause problems. One owner had a corroded fuse for the ECM on the rear run bay. Some Monacos have had problrms with bad connections in the drivers armrest. Some of those wires go to your dash readout . If you susprct thr switch for frint and rear start can it be bypassed. The wires for the Deutsch connrctors are very small? Maybe 20 ga. So low voltage can cause problems. Unlike otr trucks the wiring for the data sytem is very long. MH’s should have a better design. Hope this helps.

[moisheh]

Btw.There are some connectors and computer modules in the ceiling of one of your bays. I think the abs and maybe the Allison . Not sure.

[RVingNow]

Once you remove the abs tcm, ecu and any other module, you can measure the resistance of the bus backbone. No power can be applied for this measurement. The bus is terminated with 120 ohm resisters on each end. Measuring from a module connector (say ecu ) you should see 60 ohms, that's two 120 ohm resisters in parallel. If you find the end of the data bus a and remove the terminator the measurement should be 120.

If the measurement is off be more than a couple ohms, there's a wiring issue. Usually it's a bad connector or corrosion. Good luck

[slemnah]

Originally Posted by Naatv1

I can try that as well, should be pretty straight forward by unplugging the TCM, ABS, and VORAD modules. If unplugging them doesn't raise the voltage then I can focus on ECM again, correct?

Yes, that would be my thought.

[hypoxia]

Originally Posted by Naatv1

If i buy a good used ECU off of say eBay etc, can I have the important info removed from my current ECU and transferred to the "new" used ECU? Or if there is a better option, Im all ears.

I think so, you would need to copy the ISO file from yours and transfer it. There is some programming in the RAM of the ECU, I do not know if it is the same in all ECU's with the same part number.

Moisheh makes some good points, there are those boxes in the ceiling of my second bay.

I had some intermittent Vorad, cruise control and data problems a few years ago. I reseated a bunch of connectors & terminating resistors, replaced the clock spring, etc.. Eventually, in Mexico, I lost some DC power. I removed all of the boards in the front run bay & cleaned the corrosion. That fixed my DC power problem and oddly enough all of my intermittent problems went away.

[Naatv1]

Originally Posted by RVingNow

Once you remove the abs tcm, ecu and any other module, you can measure the resistance of the bus backbone. No power can be applied for this measurement. The bus is terminated with 120 ohm resisters on each end. Measuring from a module connector (say ecu ) you should see 60 ohms, that's two 120 ohm resisters in parallel. If you find the end of the data bus a and remove the terminator the measurement should be 120.

If the measurement is off be more than a couple ohms, there's a wiring issue. Usually it's a bad connector or corrosion. Good luck

Ive done this test and have confirmed that the resistance is in fact 60 ohms at each of the diag connectors in the front and the rear. I moved on to the next test which is the voltage test and that is the one i am failing with my engine ECU plugged in. As soon as I unplug the pigtail that leads into the engine ECU my voltage comes back into spec.

https://static.nhtsa.gov/odi/tsbs/20...51506-9999.pdf