isx12 cm2250 fuel pressure only builds if injector harness is disconnected
01-02-2021, (Subject: isx12 cm2250 fuel pressure only builds if injector harness is disconnected ) 
Post: #14
RE: isx12 cm2250 fuel pressure only builds if injector harness is disconnected
I am looking at the file you sent me.

It has active error codes for...

2374 - Low signal voltage detected at the exhaust gas pressure circuit. - (likely unplugged)

322 - Malfunction detected at injector 1 circuit. (bad/shorted out injector detected).

Neither of these two faults should be in the ecm at all... deleted programming or not. These Issues need to be solved and these 2 codes are not normal for even a deleted truck. The ECM is detecting something wrong with Injector #1. It is also complaining that the Exhaust Gas (Exhaust manifold pressure sensor) is unplugged or shorted out to ground.

- The exhaust gas pressure sensor is a critical sensor that helps control proper fuel-air-mix, proper cylinder pressures, and protected the engine, even if the engine has a delete on it. There is no reason whatsoever EVER to disable this sensor during delete programming ... not even if you are making some serious big HP mods .... It SHOULD NEVER BE DISABLED OR DEFEATED AND ONLY A BAD DELETE OR SOME COMPLETE MORON WHO HAS NO CLUE WHATSOEVER HOW THESE ENGINES RUN WOULD RECOMMEND OR ATTEMPT TO DISABLE IT AS SUCH!. - I can only assume it is unplugged due to some horrible delete programming that has been in that engine at some previous point. That or there is a wiring issue or the sensor is bad.

You should also check the feed line/circuit to the sensor as well when hooking it back up/replacing the sensor. The line feeding them off the manifold and thru the thermostat housing likes to clog up and give incorrect readings, never throwing any faults, but can cause all sorts of engine efficiency issues. Some bad delete shops will also unhook this feed-line out of sheer stupidity too.


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There are also a bunch of active emissions-related faults too. Here they are (basically) ...

3597 - DEF Controller Harness - (unplugged)
2771 - Engine Outlet NOx Sensor - (unplugged)
3314 - DOC Inlet Temp Sensor - (unplugged)
3317 - DPF Inlet Temp Sensor (unplugged)
3319 - DPF Outlet Temp Sensor - (unplugged)
1881 - DPF Delta-P sensor - (unplugged)
3134 - DPF Outlet Pressure Sensor - (unplugged)
3142 - SCR Inlet Temp Sensor - (unplugged)
3146 - SCR Outlet Temp Sensor - (unplugged)

- I can only assume that the entire harness for those systems has been disconnected. If so, then someone need to check Can-Buss #2 J1939 circuit and see if it is at 60 ohms because the engine harness does NOT contain the second terminating resistor on CAN2 ... but instead, it is located at the SCR controller. This means if someone unplugs the entire harness, then the terminating resistor is going to be missing. - The engine will still likely run, but can have some J1939 instability issues.

The terminating resistor on one end is located inside the Turbo Actuator. The other end is usually at the DEF controller or in the wire harness just past the main harness for it. The way I check the 2 terminating resistors is that I unplug the Turbo actuator harness and ohm out the (green and yellow wires) J1939 wires on the turbo actuator cable itself (not the engine side) to ensure it has its a proper 120-ohm terminating resistor internal to it. I then will ohm out the engine side of that connector to see if the green/yellow pair have 120-ohms on them as well (engine off and truck turned off). With 120-ohms on both sides of the plugs, connecting them back together makes for the proper 60-ohms. It can also be checked for 60-ohms at the "can2 weather-pack" engine harness connector on the drivers side when everything is plugged in properly.

- If either is missing, everything will run and likely not complain, but then there will be electrical noise and other gremlin issues.

That is my main concern after seeing all those aftertreatment related codes, as a lot of shops will unplug those harnesses and have no regard to the J1939 whatsoever ... and then the truck owner is always chasing ghosts, or the Turbo Actuator circuit board burns up every so often. This is because the one remaining resistor in the actuator attracts all the electrical and alternator noise and causes the board to go bad or loose its memory every so often due to it absorbing too much noise, etc. That or other ghost failures on the system, that seem to happen or come and go. I have seen a lot of trucks with this type of problems when someone unplugs entire SCR harnesses and does not install a terminating resistor at the end that was unplugged.


As far as the program you sent me... here is what else I see in it at a glance (looks like it was flashed back to stock programming recently) ...

- The program has an internal data log of the fuel pump actuator being faulty but but no actual active error code was being reported yet in the program you sent me yet. Just mentioning it, as you said it had related faults at one point earlier in the thread here.

- Aftertreaement system counter is counting up towards it, but it is not requesting an engine shutdown yet.

- Aftertreaement DPF missing system counter is counting up towards it, but it is not requesting an engine shutdown yet either.

- Aftertreaement Excessive soot Load system counter is counting up towards it, but it is not requesting an engine shutdown yet either.

- Urea Tank Level is reporting a -7 (negative 7) for its tank level. This is in error, likely the sensor is unplugged. No derates or shutdowns requested for it yet either that I can see.

- The Soot filter manager is sending requests to the main Aftertreatment manager for a regen to be performed due to not being able to read the DPF Delta-P sensor. The Aftertreatment mgr however is not requesting a parked regen yet though (most likely due to the other errors).

- Although not currently active, there are some records for Crank Case pressure darates being active on multiple occasions in the past. If the engine has had a delete program in it then the Crank case filter should have been drilled out or a maint. free one installed. - Having excess crank case pressure because someone is not changing filter often enough can and will cause turbo issues and failures as well as overhead cam/roller failures due to reduced oil pressure differential in the overhead valve train. This is clearly pointing towards an abused engine.

- There are also records for low oil pressure derates and oil pressure shutdowns in the engines past. This is not a common thing to see. This is clearly pointing to an abused engine.

- There are artifacts of delete programming that has been in the ecm at one point. - Backing up and restoring the the "features and parameters" in Inside when the engine was flashed back to stock programming did this. - i have seen this before plenty of times ... it is harmless, only a few odd control settings. Just thought that I would mention it, as I noticed it.

- The ecm is reporting that someone has performed an OBD2 fault-erase procedure on it. Likely some third-party software was used to clear faults. it is harmless, just thought i would mention it, as it is being reported in the program you sent me.

- DEF system is reporting dilluted DEF detected (likely from the harness being unplugged). Not causing a shutdown or derate at this time though.

- Urea injection manager is reporting errors but has not thrown codes for it yet. Likely due to harness unplugged.

- Urea manager reports that the DEF pump was trying to run during the ecm was last shut down.

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This is obviously not any sort of delete programming. It looks like someone flashed the ecm back to stock programming and that there is nothing indicating that the ecm is refusing to run the engine. - At least that is what it is showing me at a glance.

The engine, although should be showing several faults in the dash, should run and idle the engine according to what i see in the program. It should be stated though that the ecm program itself only contains a limited view of what is actually going on.


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RE: isx12 cm2250 fuel pressure only builds if injector harness is disconnected - Rawze - 01-02-2021



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