Service DEF, Regen Required... Just Kidding??
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by DieselDisciple, Jan 22, 2021.
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Thanks everybody for the replies. I will be looking it over really well on my 34. Maybe I can find an obvious problem ... will post updates.
DJMech Thanks this. -
DieselDisciple Thanks this.
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DieselDisciple Thanks this.
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The symptoms you are describing, where it asks for a regen and threatens to derate, gives a bogus Nox code and then all of a sudden goes away, is a wiring harness problem. Cut and dry.
If you bring up the soot level gauge on the dash, where it says "A 2 3 4", the level will be between the 2 and 3, which is about 130% plugged when you look at the value with Premium Tech Tool. Then, as you're driving down the road it will all of a sudden turn off the regen light and the soot level will drop to 50% or less. This is because the wiring harness makes the connection again.
I'd suspect that along with that Nox code, there are also CAN bus "data erratic" codes.
Every inch of the wiring harness needs to be inspected where it rubs up against any metal or is attached with a zip tie to a metal bracket. Then if no obvious chafing damage is found, unplug absolutely every single wiring connector you can get your hands on (after disconnecting the batteries), inspect for corrosion, apply a bit of silicone spray to them and reconnect. Pay particular attention to all the connectors and wiring around the DPF. Those wires live in hell.
Also with Nox codes, you mentioned you just got that truck? That particular code might be from old DEF. Let it run down pretty low and then refill it with fresh DEF.D.Tibbitt, TokyoJoe and DieselDisciple Thank this. -
As far as def goes I have run it down to empty and refilled it already thinking the same thing.
I'm off to check wiring, connectors, sensors etc. Thanks everybody for the replies. Here we go... -
Ok... checked every wire and cleaned every connector I could find. Didn't find any chaffing. Removed and inspected NOx sensors, they are remarkably clean, no carbon buildup. Thats a good sign. I know they could still have internal failures but I don't think that is the issue. I also checked connections for DPF pressure sensor and tubes. Tubes are clear and connections are clean. No chaffing.
Didn't see any exhaust leaks anywhere. Good sign. Also pulled the turbo-CAC pipe to view inside as it looked like I had some oil around the boots. Its clean as a whistle. Whew. I thought it would be but checked anyways.
I checked for bad connections and chaffing around batteries (plus the little wires with fuses) and ecm. Cleaned em all but everything looks good.
I also removed the def doser to see if there was any buildup on it or internally. Its also pretty clean.
I hope messing with all the electrical connections did the trick. Hope it'll run well for me until I can get to somebody who can read a Volvo.
Anything I missed? -
D.Tibbitt Thanks this.
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If you repair it correct only 1 time though he isn't going to have more problems in the future. Who wants to keep unplugging it and plugging it back in?
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