late 2007 6.7 problems
 

I bought this truck a short while ago for a trailerpuller since my old Chevy 6.5TD was not adequate in the Rockies on the last trip we took. Bought it for the engine, hate it now for the same reason. Good price, ran fine, estate sale so no answers to service questions. Check engine light was on, said they had it at dealer "no problem".
Tried to read codes by on/off technique after studying this forum-did not work. Got code reader and hooked it up today-here is list of codes:
U010C-unknown
P003A-turbo boost exceeded learning point
P2141-EGR throttle control circ A low
P0102-Mass flow A circ. low
P0487-EGR throttle control circ A/open
P2A00-O2 sensor circ range/perf bank 1 sensor 1
P2A01-O2 sensor circ range/perf bank 1 sensor 2
P040D-EGR temp sensor A circ Hi

THis was after taking a trip pulling travel trailer. Truck would run fine for a while, then run rough, no smoke, nothing unusual on guages or indicator lights. On the way home got 90% message on overhead display, also "service needed". Has not shown 90% message again. I was planning on doing delete and mild tune on this truck, but now am just trying to get some idea of what is going on so I can figure out what to do next. At least my old Chevy and farm tractors were pretty simple to diagnose, and have never had this sort of problem with them.
Any and all help will be much appreciated.
Thanks,
PR

You could have a turbo actuator issue, on your year and model it is non serviceable which means turbo replace may be required. Follow diagnostics for U010C code, try disconnecting turbo actuator and clearing codes, do codes return? Refer to diagnostic test for that code first.

Thanks for the reply. The turbo seems to work OK-I get boost, engine brake seems to work, used it when pulling trailer. I looked at turbo prices and they were quite a shock, compared to the last time I had to replace one. Is there a way to check actuator operation? I thought I read that a while back but could not find it today.
Thanks,
PR

Do the diagnostic first before you start looking for a new turbo. The actuators are replaceable but the problem is it's hard to find a good aftermarket one and then finding someone to calibrate it for you.

I do know of a place in Texas you can send the turbo to to have the actuator replaced but some have had mixed results.

There's alot of open circuit codes that can mean wiring issues.
Have you checked out all the emissions equipment yet just to see if it's all there? You can check this out for reference: 6.7L Cummins Emissions System Explained and for the egr: https://www.dieseltruckresource.com/...-right-273345/
Let us know if it's all there.

I crawled under truck and verified that sensors on exhaust system are installed and plugged in. Same for EGR devices on intake. I cleared faults and had 4 come back, U010C, P2141, P0102 and P0487. Those seem to come back immediately without starting engine. I was planning to delete the whole mess anyway, will deal with turbo after that.
Thanks,
PR

102 (maf sensor circuit low) and 2141 (egr air flow throttle control circuit low) are both circuit low codes so there's a short in the main harness that goes to them. 487 (egr Airflow Throttle Control Circuit A Open )( it's really the throttle control valve) sounds like there's a broken wire in the harness. The harness splits and goes to both locations but a short somewhere in the harness can drag down the sensor voltages.

For diagnostic tests and connector drawings for the codes you can go here and download the service manual in the article section at CarboniteCummins - Home

The Mass Air Flow Sensor, EGR Airflow Control Valve and Turbocharger Actuator get a 12V power supply from the Smart Power Relay. Disconnect one component at a time until you find the one that is shorted. The turbo actuator would be my guess, disconnect it and clear codes. If no other codes return except turbo code you found your problem.

Gentlemen I appreciate your patience and information. After printing out relevant pages of service manual I understood what you meant by the common feed from the "smart power relay. I finally found that on my truck, this is fuse #37. I have replaced the fuse and all the faults cleared except U10C, so at least I can focus on the turbo actuator. Is it possible to remove cover of actuator and check driven gear/arm for binding? And if I have to replace turbo, what has to be calibrated?
Thanks again,
PR

2007 model year do not have turbo actuator replacement. Complete turbo will need to be replaced. No calibration needed with new turbo since it comes with actuator already installed and calibration is not required. If you buy a REMAN make sure it has a cleaning port.

Thanks for the info-it's been quite a learning experience! Guess I will start looking for a turbo.
PR

A year ago they were $1100 from Pensacola Diesel. Rebuilt with new actuator.

A few questions about the turbo situation:
Turbo seems to be functioning normally-good boost, good engine braking. 1. Besides fault code, what is actually going on with turbo assembly?
2. What will happen?
3. When this gets replaced, can it be replaced with a unit from a later year that has a repairable/replaceable actuator?
PR

It does sound like the actuator is bad or at least there's a wiring short in the harness so make sure you do the wiring checks in the diagnostic (if there are any) before replacing the turbo.

If there's an issue with the actuator/wiring then the turbo isn't delivering the desired boost when it happens. This is probably what happened when you got the dpf 90% message since with too much or too little air you will get poor combustion and creat a lot of soot and fill the dpf.

If it continues to malfunction then you will fill/plug the dpf. Worst case scenario is it will stop functioning.
Both of these cases will strand you somewhere you don't want to be.

Yes you can (and will) replace it with a newer model that has all the upgrades they've done over the last 7 years.

DPF will soon not be relevant, it is going to disappear.
I have a few more questions, I have been around and replaced turbos for many years, but none of them had wires going to them, only oil and sometimes coolant, so I am hoping to get a better understanding of how these work.
I have checked for voltage at connector, had 10.? at plug-not quite what troubleshooting guide called for, but truck had been sitting with key on for quite a while. I did not have the nerve to try to find the plug going to the ECM and pull it, so have not checked communication lines yet. What signal is the ECM getting or not getting to generate the 10C fault?
What is the actual moving portion of the turbo, and what is it's function? (I was under the impression that it controlled back pressure for engine braking.)
Thanks,
PR

The service manual has a great section on testing the turbo with connector diagrams and what to expect for resistance and voltage etc. It's a great resource.

For the basic function go here: Holset's Variable Geometry Turbos.