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Old 01-19-2020, 12:48 AM   #1
markxengineering
 
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Default wiring harness failure details (for reference)

I had been chasing codes related to intake pressure sensor and O2 sensor for the past year. Replacing the components did not help. The problems were intermittent, and each time I checked the signals or the harness everything seemed fine. I could clear the CEL, be fine for a anywhere from 1 minute to several months, but always CEL and codes would return.

Finally, about a week ago, I stalled on the highway, luckily in a non-dangerous spot. The engine would re-start after key-off, then stall again a few minutes later. Codes at that point were as shown here (Cylinder 5 injector was the only new one)

I removed the injector cover, wiggled all the wiring I could, including harness stalk down by the fuel filter, and magically everything was fixed. But clearly I needed a new harness.

Here is the old harness, with a couple problem locations identified.




A new harness from a local Mercedes dealer was $560 or so, wholesale price, they had it next day. It would have been over $800 from dodge for the same part. Installation was time consuming, took me longer than it took some, but I'm a bit meticulous and have big hands. I'd say 1.5 complete days for me. The most difficult connector to figure out was the AC compressor. It's the only connector without a "clip" to release, you just pull/pry it straight out. I spent a while looking for the non-existing clip. The rest were all easy, just some tight spaces and making sure not to damage brittle, old plastic.

This is the only wiring failure of this type I've seen, and the only time I've had a vehicle shut off entirely for such a silly reason. IMO this contributes to the "finicky" reputation of the Sprinter- too bad they couldn't have done a better job with disabling only the failing injector circuit (much safer than engine shut off) or built a better harness in the first place. I guess this is an issue with other diesel's as well, but all my prior experience is in gasoline engines, never seen anything like this.


keywords 2030-002 2026-002 2036-001 2036-002 0205-008
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Old 01-19-2020, 02:29 PM   #2
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Default Re: wiring harness failure details (for reference)

Thanks for the information and details.

Was the green arrow area failure where the harness is cable tied in the area of the fuel filter?

T1NharnessFail01.jpg

T1NharnessFail02.jpg

T1NharnessFail03.jpg

vic
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Old 01-19-2020, 03:49 PM   #3
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Default Re: wiring harness failure details (for reference)

Sure was
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Old 01-19-2020, 04:03 PM   #4
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Default Re: wiring harness failure details (for reference)

Quote:
Originally Posted by markxengineering View Post
I had been chasing codes related to intake pressure sensor and O2 sensor for the past year. Replacing the components did not help. The problems were intermittent, and each time I checked the signals or the harness everything seemed fine. I could clear the CEL, be fine for a anywhere from 1 minute to several months, but always CEL and codes would return.

Finally, about a week ago, I stalled on the highway, luckily in a non-dangerous spot. The engine would re-start after key-off, then stall again a few minutes later. Codes at that point were as shown here (Cylinder 5 injector was the only new one)

I removed the injector cover, wiggled all the wiring I could, including harness stalk down by the fuel filter, and magically everything was fixed. But clearly I needed a new harness.

Here is the old harness, with a couple problem locations identified.




A new harness from a local Mercedes dealer was $560 or so, wholesale price, they had it next day. It would have been over $800 from dodge for the same part. Installation was time consuming, took me longer than it took some, but I'm a bit meticulous and have big hands. I'd say 1.5 complete days for me. The most difficult connector to figure out was the AC compressor. It's the only connector without a "clip" to release, you just pull/pry it straight out. I spent a while looking for the non-existing clip. The rest were all easy, just some tight spaces and making sure not to damage brittle, old plastic.

This is the only wiring failure of this type I've seen, and the only time I've had a vehicle shut off entirely for such a silly reason. IMO this contributes to the "finicky" reputation of the Sprinter- too bad they couldn't have done a better job with disabling only the failing injector circuit (much safer than engine shut off) or built a better harness in the first place. I guess this is an issue with other diesel's as well, but all my prior experience is in gasoline engines, never seen anything like this.


keywords 2030-002 2026-002 2036-001 2036-002 0205-008
The issues you have cited are quite common and we replace T1N harnesses at about one per month.
In fact we have go it down to a fine art form.
3,5 hours labor for a 2004 to 2006 model and 4,5 for a
2002 to 2003 T1N.

The reason for "finicky" as you put it is the German Auto Industry instance on using "twisted pairs" instead of shielding on certain vital circuits. That fundamental concept plus a basic philosophy of material cost, recycling and planned obsolescence (mid 90's MB platforms a typical example) all adds up to highest incidence of harness repair/replace intervention to correct driveability faults than might be regarded AS NORMAL. Noting in any diagnosis task incidences, very high resistances, and shorts, due to self abrasion of twisted pairs and environmental attack over time are often customary discoveries .

In contrast take Toyota and their harnesses made by Sumitomo being some of the BEST/Durable in the business and when you need it! Where pure computer stabilized voltage & data signal control is required on platforms like the Prius.

On Domestics the Ford principal of harnesses being manufactured to ISO 9000 standards ensure you get a lifetime durability on most stuff unless its been DIY "dicked" with.

So Ford & Toyota are top of the pile with German brands coming in as runners up in the electrical field races (excuse the pun) .(Shielding used, not twisted pairs for the most part.)
Now you know why (in part) why Linden fixes Euro based vehicles the most part .
Dennis
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Old 01-19-2020, 04:34 PM   #5
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Default Re: wiring harness failure details (for reference)

I was under the impression that an injector open circuit wouldn't cause stalling, but maybe a grounding even would? Regardless, thanks for posting.
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Old 01-20-2020, 03:19 AM   #6
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Default Re: wiring harness failure details (for reference)

I’m pretty sure it was short to ground rather than open, but easy to check by unplugging an injector next time cover is off. I don’t think it will stall but not 100% sure either.
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Old 01-20-2020, 03:04 PM   #7
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Default Re: wiring harness failure details (for reference)

Quote:
Originally Posted by markxengineering View Post
Iím pretty sure it was short to ground rather than open, but easy to check by unplugging an injector next time cover is off. I donít think it will stall but not 100% sure either.
For the OM647 engine one injector at a time can be unplugged, or open circuit and the engine will continue to run. That is not true for the OM612 engine. There is a voltage kickback between/among injector circuits which is necessary. Unplugging even one injector on the OM612 engine causes immediate shutdown.

An injector harness short across or to ground isn't an open circuit.

vic
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Old 01-20-2020, 03:25 PM   #8
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Default Re: wiring harness failure details (for reference)

Are there any preventative measures an owner can take to reduce this vulnerability?

Observing/inspecting the bundle next to the fuel filter has proven inconclusive in my case. Does the bundle typically exhibit obvious abrasion damage?

I have no driveability issues. Just looking to prevent them.
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Old 01-21-2020, 09:44 PM   #9
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Default Re: wiring harness failure details (for reference)

Cut the zip tie where the main stalk has its lowermost attachment near fuel filter. I’ll post a pic, that’s where mine wore right through the black skin then the wire insulation too.
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Old 01-22-2020, 01:50 AM   #10
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Default Re: wiring harness failure details (for reference)

The other high abrasion point is the column shaft rubbing on the harness.
Causes the van to cut out when turning a corner.
Dennis
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