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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 4856
Experience:  Owner at DJ Wilson
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We have 2 mitsu with the same code P1421 and P1422 and we

Customer Question

we have 2 mitsu with the same code P1421 and P1422 and we had the DPF filters baked and cleaned at dealer , installed them and still have codes
Submitted: 11 months ago.
Category: Medium and Heavy Trucks
Expert:  Wayne replied 11 months ago.

Hi I'm Wayne

I will help you with this

Code P 1421 is clogged or dirty Catalyst (muffler)
Code P 1422 is Temp. Sensor Has Failed ( this is exhaust manifold, or muffler pipe
This will set off engine warning Light, Poor acceleration
and no power

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Customer: replied 11 months ago.
According to manual both of those codes are clogged dpf filters 1421 is for clogged and 1422 is severe and as i said we had them cleaned and baked at dealer and code is still there
Expert:  Wayne replied 11 months ago.


Manual yes and No

it is basic info as you are finding out

I suggest you replace the Temp sensor

this will solve your your issue

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Customer: replied 11 months ago.
OK which one each system has 3 temp sensors, and when we have the computer hooked to it before we start it (them ) the computer will read 2 temperatures and when the truck is started we can watch the temperature raise and using a temp gun they pretty much mimmick the temp the computer readings. There are 3 sensors and 2 readings forward and middle the rear does not read when we unplug it none of the temperatures change
Expert:  Wayne replied 11 months ago.

Thank you for that

it would be the rear one


Customer: replied 11 months ago.
replaced rear sensor fault still there
Expert:  Wayne replied 11 months ago.


That should have cleared it

I am going to opt-out and send back to the board for another

expert, don't reply or rate me as that will lock the question back to me

Sorry I could not help you

Expert:  Daniel Wilson replied 11 months ago.

Hi Gregory, Its Dan. If the DPF is serviced and the sensors and harness are confirmed good the next step is to have the ECM reflashed/reprogrammed with the most current updates which will also reset the system and then see if the faults return indicating there is still an actual problem. Sometimes a software update/reflash is needed to reset the system. Let me know

Customer: replied 11 months ago.
i guess everything we did was for nothing and a waste of money it still has to go to the dealer
Expert:  Daniel Wilson replied 11 months ago.

Hi Gregory, This site is for informational purposes. We are here to help answer your questions. We are not employees of the site but users of the site just like you are. Your deposit sits with the site not the experts answering your questions or taking the time to try to help you. neither of us got paid a dime for our time helping you. Experts get a percentage on positive feedback and accepted answers so when there is no rating the experts do not get paid. My answer is what needs to be done if you have confirmed your repairs are complete but the ECM is not resetting on its own after an attempted Regeneration. Your question history and rating history remains with the site for all experts to see and I do know that there are some on the site that got some great help and technical info from experts but have a long history of never rating and they over time have a tough time getting the experts to spend the time to help them. It is a great tool to have when you can access many years of experience a knowledge on the site at a lot less than an hours diagnostic charge at a shop. Either way. No one has been paid here and your deposit is with the site. Good luck to you sir.

Customer: replied 11 months ago.
ECM was re flashed at dealer on one of the trucks , still has same code we have truck back now, all 3 temperature sensors have been replaced, DPF has been baked cleaned and tested. We are now looking into the wiring , still has clogged DPF code I know Wayne said it was temperature sensor so we changed all three eventually we are thinking it has to with the the sensors that measure the back pressure and not the temperature do you have any information on the pressure sensors such as ohm readings we should have for good sensors compared to bad sensors we do not want to buy all of the pressure sensors if they are not bad like we did with the temp sensors, we have had this truck in and out of the shop for 3 weeks and are losing money and possibly a customer if we do not get it fixed soon . We will have to eat the temp sensors and the dealers cost to regen it but it is better than losing a customer. Do you know of a diagnostic computer that will let us get into the sensors on a mitsu we have the snap on pro link ultra it will only read OBD11 on mitsu it will let us get into Isuzu but not Mitsu. I am trying to find out if the MUT111 would let us manually regen and get into the sensors so we would be able to isolate the problem instead of throwing darts at it very frustrating thanks for any help you can give
Customer: replied 11 months ago.
were you able to find out what we should have for resistance in the sensors for the def?
Expert:  Daniel Wilson replied 11 months ago.

What is the full chassis model and engine make and model? Ill have to see if my books have that information. Experts arent employees of the site so I will have to check in between jobs as time allows. I help on here evenings, in between jobs, some weekends as time allows.

Expert:  Daniel Wilson replied 11 months ago.

Hi Did you get this resolved?

Customer: replied 11 months ago.
Truck sn JL6HLM1E981K013008

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