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2012 Isuzu nqr has codes u029d loss comm. with nox #1 /

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u029e loss comm with nox...
2012 Isuzu nqr has codes u029d loss comm. with nox #1 / u029e loss comm with nox # 2/ p1464 main relay performance / p0707 transmission range switch low voltage. none of them are current, truck has no drivability issues any help would be great
Submitted: 4 months ago.Category: Medium and Heavy Trucks
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3/20/2018
Technician: Jeremy, Certified Truck/Bus Technician replied 4 months ago
Jeremy
Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3,858
Experience: ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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My name is ***** ***** I will assist you with your question today.

I'm an independent contractor and I don't get paid until a rating has been made.

We can go back and forth as needed to help resolve the issue you are having. Follow-ups are free after ratings, so rate with confidence!

Are you just needing the code meaning? If these are not causing issues and old codes, reset the memory. These do stay in the system and will reset themselves is why they are old codes. The communication loss codes would derate the engine if they were active. The only one that wouldn't cause a derate is the p1464, but the rest will if active recently. Those 2 u codes would have the check engine light on and the regen light on if they were active recently. With both of them active, the NOx wouldn't read at all and the regen wouldn't run. They may be old codes that were not cleared.

If you want the code info, I can pull and list it for you if needed.

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Customer reply replied 4 months ago
ok I can send you any live data you need. the codes are history and not active and no check engine light on however this is the second visit to shop and cel does come on intermitantly and power down intermitanly so I am hesitant on clearing cause I already tried this and they came back. Jeremy as you know I will tip you very well if you stay with me and guide me through. I am using a factory idss program. just not sure how to proceed also that last code the temp range low voltage I need to deal with .
Technician: Jeremy, Certified Truck/Bus Technician replied 4 months ago

Are they the same codes when the vehicle returns?

On the p0707, if that is a nuisance, replace that switch first. It does come and go intermittently. That one will definitely do that to you. The second one that does that is that stupid fluid pressure switch. It gets little pieces of metal in there and it will trigger that inhibit. Most times, it is that switch on the side of the transmission that will cause it. I would check it first since it will kick the CEL and cut the power out.

On the others coming back, check for voltage shorts at the battery connections before moving on. That p1464 does power the DEF system. That one you will want to follow the troubleshooting tree for I believe it will have you check the ground first since it is a common Isuzu issue with it. Then it will have you check the pins for the module. That p1464 will cause the other 2, but if it is intermittent, it will be the ground or the harness pins most likely. I have only run into that code being one of those 2 spots.

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Customer reply replied 4 months ago
When you say ground do you mean battery ground or for the module its self? Since I see it has 3 grounds coming out of the harness that goes to the module and they are bolted to the frame. Also I checked the module connectors and didn't find any corrosion. I also checked for continuity to chassis ground at the module connector pins 1,2,3, and 4 and had 0 ohms.
Technician: Jeremy, Certified Truck/Bus Technician replied 4 months ago

The module itself. It will act up at the ground connection on the frame. I remove the nut, clean, and put back on, then paint over.

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Customer reply replied 4 months ago
ok I have full communication with this truck however it is actively derated to 5 mph. the "exh. system" red is illuminated in the mid in center of cluster but idss shows no history codes and no current anything. the amber low def light is flashing very fast also. however the def is almost full and when I view live data it is also showing full. not sure were to go its odd I have no codes and no engine light. maybe there is a fuse or something im stuck
Technician: Jeremy, Certified Truck/Bus Technician replied 4 months ago

Can you see the connection to the Aftertreatment module? Tha almost sounds like the aftertreatment module is having power on issues or the module is shot. I think there is even a TSB on that, but I can't see the TSBs from here. That will be a dealer that would ned to list them out.

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Customer reply replied 4 months ago
I can see the module I suppose I can see the connection also, i tried doing a def injector leak test it passed i did a manual regeneration it worked just cant seem to get this light to clear even for a second, the truck dint come in for this there was no exhaust ight on it just seemed to happen.
Technician: Jeremy, Certified Truck/Bus Technician replied 4 months ago

That is really odd to have the light with no issues.

Was the truck test driven yet to get it to self test at the 20 mph? That may be the missing step for it.

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Customer reply replied 4 months ago
ya that's a problem as it wont go faster than 5 mph
Customer reply replied 4 months ago
ok Jeremy problem solved, as it turned out my tech had crossed some wires in the dash, removed dash put wires were they belonged re hooked up lap top and now it had more problems than a math book, (wich I was hoping for) so I cleared them all and all is good test drove 30 miles no issues thank you for staying with me
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