Spartan Chassis DEF Failure, looking for a new wiring harness

[McGruer]

I recently purchased a 2013 Entegra Coach, Aspire 42DEQ which is on a Spartan Chassis with Cummins 450 diesel engine. After about 1,000 miles I had an engine failure code SPN 3362 FMI 31, Aftertreatment 1 DEF Dosing Unit failure. We changed the Dosing Unity and got a new code showing low voltage indicating a short in the wiring harness. After troubleshooting we found that one of the pins in the wiring harness might be lose and causing the short. I have been searching for a new wiring harness. Does anyone know of a place where I can start searching for a new DEF wiring harness?

[757driver]

Originally Posted by McGruer

I recently purchased a 2013 Entegra Coach, Aspire 42DEQ which is on a Spartan Chassis with Cummins 450 diesel engine. After about 1,000 miles I had an engine failure code SPN 3362 FMI 31, Aftertreatment 1 DEF Dosing Unit failure. We changed the Dosing Unity and got a new code showing low voltage indicating a short in the wiring harness. After troubleshooting we found that one of the pins in the wiring harness might be lose and causing the short. I have been searching for a new wiring harness. Does anyone know of a place where I can start searching for a new DEF wiring harness?

I would start with Spartan, they are the ones that built the chassis and installed that harness so they should be able to help you source a new one.

[mackwrench]

The connectors/pins are serviceable. Pins can be removed from the connector and replaced without removing the harness. Depending on the type of pins, a few special tools are needed to remove the pins from connectors.

Can you post a picture of said connection? Also google / YouTube the replacement procedure.

[McGruer]

Originally Posted by mackwrench

The connectors/pins are serviceable. Pins can be removed from the connector and replaced without removing the harness. Depending on the type of pins, a few special tools are needed to remove the pins from connectors.

Can you post a picture of said connection? Also google / YouTube the replacement procedure.

Thank you for the response. The mechanic has the tool to replace the pins but, believes that it isn't just the pins. They replaced the pins and the low voltage error code still existed. They believe that there is a short in the harness and believe that they have isolated the wire that may be shorted. Right now they are going to run a new wire in place of the wire showing low resistance. I went in to talk to the Cummins dealer in San Diego and they were extremely helpful. They said that the wiring harness was not a Cummins part but, started researching who installed it in my RV. Spartan was no help as he was just passed on from one department to another. After 45 minutes he said go ahead with the wire fix and he will continue researching. He did say that the wire was a band aid fix to a more serious problem. Replacing the wiring harness would be harness would help locate where the short is and insure the we don't have another short. I am hoping that the mechanic will be giving me good news tomorrow with the new wire.

Entrgra Couch is working on getting the information to I need but, it is taking time was we are working through messaging posts.

[Dav L]

The normal way to isolate is to test sections of the wire to isolate where the issue is. Once found, it's easy to fix.
Look at the schematic to see if there are any connectors / splices along it's path. That's the first place to look for disconnects.
Look at the harness for rub spots. And for spots that might have been stretched.

Not sure what "band aid fix" means. And because one wire in a harness is pinched / broken, not super good odds another is. But a physical inspection of the entire harness should point that out.

More likely it's at the ends near the connector. The extraction tools are readily available on amazon / ebay. Good for any RV tool box.

[McGruer]

Originally Posted by Dav L

The normal way to isolate is to test sections of the wire to isolate where the issue is. Once found, it's easy to fix.
Look at the schematic to see if there are any connectors / splices along it's path. That's the first place to look for disconnects.
Look at the harness for rub spots. And for spots that might have been stretched.

Not sure what "band aid fix" means. And because one wire in a harness is pinched / broken, not super good odds another is. But a physical inspection of the entire harness should point that out.

More likely it's at the ends near the connector. The extraction tools are readily available on amazon / ebay. Good for any RV tool box.

Just spoke with the mechanic. Very frustrating. They bypassed to suspected wire and the low voltage condition still existed. They said that the wiring harness is intertwined with other connections and seemed to think it would be difficult to remove the entire wiring harness. Not sure about that but, it seems like that is t he next step. The owner of the repair facility did speak with someone at Spartan and they said that it would take 12 to 14 weeks to rebuild a wiring harness. I'm going to try to reconnect with Spartan to see how accurate that is. very frustrating because we just moved into the RV fulltime in June.

[mackwrench]

I'm probably of no help, but the ECM is supplied by Cummins. That means the harness really ain't that special to your coach, only length to after treatment may matter. The connection at ECM and any sensors are same on most all those engines. ....The diagnostics are same..

Cummins has a breakout box that is plugged into the harness to check for and locate open/shorts in the harness.

Also are you sure you the circuit in question really has low voltage? Many control circuits will be low (5V) voltage or even supply ground based on sensor resistance. I ask this because in your post, you say tech had wire with "low resistance" ....not open (cut) not high resistance (short to ground)...

My saying this is are you sure the shop is capable of this level of diagnosis. How are they measuring the "voltage"?

Easy to get in a peeing contest between Cummins, the chassis mfg, the coach mfg and your repair shop....be careful you'll have 10k of diagnostic time in a 30 min repair.

Just a wag, but I'd make double sure the engine to chassis ground is good, and checked with a Ohm meter., Then unplug the harness at both ends, including sensors, check continuity for every wire in harness, takes a lot of patience to diagnose wiring, even more when you can't see all the harness.

Good luck, keep us posted.

[Dav L]

Yup, what mackwrench said.

You have an unqualified mechanic. He / she isn't a diagnostician.
They easily could have checked for continuity on the wire before replacing it.

Do they have the wiring schematic? If not, then you are paying for the poke and hope.

Do YOU have the schematic for your rig? Vital.

Get the rig out of there or insist on a true "A" diagnostic tech be assigned to work on it. Sounds like they have a C tech working on it.

This isn't rocket science if they have the schematic and IF they understand the circuit function.

BTW, loose connectors almost never cause a short. They cause Opens.

Next they will be suggesting to remove the radiator cap and roll a new RV in and put the cap on it and call it fixed...

[McGruer]

Originally Posted by mackwrench

I'm probably of no help, but the ECM is supplied by Cummins. That means the harness really ain't that special to your coach, only length to after treatment may matter. The connection at ECM and any sensors are same on most all those engines. ....The diagnostics are same..

Cummins has a breakout box that is plugged into the harness to check for and locate open/shorts in the harness.

Also are you sure you the circuit in question really has low voltage? Many control circuits will be low (5V) voltage or even supply ground based on sensor resistance. I ask this because in your post, you say tech had wire with "low resistance" ....not open (cut) not high resistance (short to ground)...

My saying this is are you sure the shop is capable of this level of diagnosis. How are they measuring the "voltage"?

Easy to get in a peeing contest between Cummins, the chassis mfg, the coach mfg and your repair shop....be careful you'll have 10k of diagnostic time in a 30 min repair.

Just a wag, but I'd make double sure the engine to chassis ground is good, and checked with a Ohm meter., Then unplug the harness at both ends, including sensors, check continuity for every wire in harness, takes a lot of patience to diagnose wiring, even more when you can't see all the harness.

Good luck, keep us posted.

I am a total loss with this. I was a backyard mechanic a long time ago but today with computers, onboard diagnostics, and sensors I am in a fog.

I spoke to Cummins and they said they have no part number for the ECM/DEF wiring harness. The mechanic that I spoke to said that wiring is provided by Spartan. As of Friday, Spartan has a tech that will be contacting the repair facility to assist. We'll see where that goes.

I suspect that you're correct about the mechanic. This is above their skills. The responses that I am getting are not consistent with what I am getting from my research. It sounds like they are doing a hunt and peck kind of diagnosis.

I suppose that is what happens when you breakdown near a small town on the freeway. Eloy, AZ is a small gas-stop along the I-10 and although this shop seems to have a lot of business it doesn't seem like they get much of this kind of work.

I will take any advice I can get to understand and be better involved as this process continues. Right now the shop is telling me that their contact with Cummins/Spartan is saying it will take 12 to 14 weeks to get a replacement wiring harness. They replaced the suspected wire in the wiring harness and the check engine condition still exists.

[McGruer]

Originally Posted by Dav L

Yup, what mackwrench said.

You have an unqualified mechanic. He / she isn't a diagnostician.
They easily could have checked for continuity on the wire before replacing it.

Do they have the wiring schematic? If not, then you are paying for the poke and hope.

Do YOU have the schematic for your rig? Vital.

Get the rig out of there or insist on a true "A" diagnostic tech be assigned to work on it. Sounds like they have a C tech working on it.

This isn't rocket science if they have the schematic and IF they understand the circuit function.

BTW, loose connectors almost never cause a short. They cause Opens.

Next they will be suggesting to remove the radiator cap and roll a new RV in and put the cap on it and call it fixed...

I have the schematic for the chassis but, not for the rig. I will search to find one. I'm not sure that I am working with the best but, that is what you get when you breakdown on the freeway between big cities. The shop is in a one offramp city between Tucson and Phoenix. That is where I was towed. Now I have to look into possibly moving/towing the rig to a qualified shop, paying for the work they have done so far.

[darjacob]

I had much the same problem. Took it to Cummins and they "overlaid" several wires over the harness. that means they ran new wires and tied them to the original harness. Solved the problem.

[Dav L]

I sure am hoping that in a month they were able to trace the wires, fix the break and get the OP back on the road.

OP - what ended up happening?

[Jburklo]

McGruer

Any update. Also what code did you receive? I have been having a similar problem and have been intermittently receiving the SPN3610 FMI4 code. Did not cause a de-rate and I was able to drive another 300 miles. I talked to Cummins and they suggested the same harness but also said it was a Spartan harness. I was getting ready to start the harness search and just found your post. Additionally you might check Cummins. They recently had and still do have a technical service fix on the DPF/SCR. I had mine replaced but after about 1000 miles the dreaded Spn3610 came on again.

Please let us know the use pdate. Hopefully it’s fixed and you can share the fix.

Regard.