Code 1894 Now what?

[tree98]

(01-28-2020 )Lonestar10 Wrote:  he uses a 3.6amp headlight and probes in and sees if it lights up. a test light is only something like 350-700 miliamps and is much easier for a circuit to light up.

Uni taught me this trick too. Something I never thought of but makes perfect sense. I was using a meter though not just a light but same principal.

[Moose]

(01-29-2020 )farmer70 Wrote:  So it can be inactive and everything will work ok? But if it is something really serious it will stay active?

That is correct. When it's active, it's just that, an active fault or problem with the system. If the problem is intermittent, a hiccup or a moment of bad communication on the truck's part you will have the MIL lamp intermittently turning on and off and instances of high inactive counts in the fault code history.

(01-29-2020 )farmer70 Wrote:  That code about the DEF unit was weird because it was full of DEF truck was bumped up to about 1100 rpm and out of nowhere the DEF light inside the DEF gauge comes on, the message center screen says DE RATE eminent. It was cold that night I wonder if it had something to do with that?

That you only have one count each of 3497 & 3559, I'd dismiss that as a momentary loss of B+ power to the aftertreatment system. (loose connection, bad relay, etc.) The 1894 could become an issue but as said above I'd start with the wiring and connections before condemning something way more expensive and should be checked anyway including the CECU inside the dash. The 4289 could be related as Paccar multiplexes the throttle signal through the CECU.

[JimT]

(01-29-2020 )farmer70 Wrote:  So it can be inactive and everything will work ok? But if it is something really serious it will stay active? That code about the DEF unit was weird because it was full of DEF truck was bumped up to about 1100 rpm and out of nowhere the DEF light inside the DEF gauge comes on, the message center screen says DE RATE eminent. It was cold that night I wonder if it had something to do with that?

So when the engine computer (ECM) detects a problem it sets a fault code. As long as the problem is still being detected it is considered an "active" fault. When the problem is no longer detected it becomes an "inactive fault". The ECM keeps track of how many times these faults are triggered and a lot of information about the engine at the time of the fault. The dashboard display only shows "active" faults. But all faults, active or not, are stored in the ECM until manually cleared with a program such as Insite.

Everything the ECM knows about the engine and related systems is based on electrical signals from various sensors. So, when the ECM detects a fault there are 4 possible reasons:
1) the component being monitored is malfunctioning.
2) The sensor is malfunctioning .
3) the signal from the sensor to the ECM is being interrupted and/or changed.
4) The ECM is malfunctioning.

#1 and #2 are equally likely to be a problem and in some cases #1 and #2 are the same physical part. #3 would be the next likely candidate. And finally, in rare cases #4 could be the actual issue, although it's not likely.

So, in the case of the DEF level this would mean:
1) The fluid level in the tank has dropped too low.
2) The sensor that measures/reports the fluid level is no good.
3) There's a problem with the wires between the sensor and the ECM OR between the power supply and the sensor.
4) The ECM is malfunctioning.

You said the tank was full, so #1 can be eliminated. #2 would be you next suspect. However based on your descriptions of events, #3 should be investigated as a possible suspect.

In any case, the troubleshooting steps in insite/quickserve will help you to go through and investigate the issues in a logical fashion and they usually explain how to perform the different tests so no prior experience is required (just like most "techs" at the repair shops).

You're on the right track, you have the information you need to start troubleshooting the problem(s). Now it's up to you to either do the work yourself (always the best option) or find a competent shop that you can pay lots of money to do it for you (not the best option, but we all have limits to our abilities). If you do go with a shop doing the work, then take some time and find a GOOD shop that will actually do the proper troubleshooting BEFORE replacing any parts. Some shops will see that code for the turbo and tell you you need a new turbo. But your problem could be as simple as a corroded ground wire or a wire that has rubbed through and is shorting out occasionally.

[Rawze]

just need to keep in mind,

turbo 'popping' and voilent reversing of the impeller is NOT AN ELECTRICAL ISSUE!!!!!

http://rawze.com/forums/showthread.php?t...4#pid49254