Cummins ISX CM871 Regen Temps Question

Reviving a old thread. I been looking at a friends truck... it's a 2011 with a CM871. The truck does not throw any fault codes. His DOC temperature is not increasing more then 440F. Shop installed new sensors on the doc and dpf. Prior to asking for my help, his DOC was removed and checked by a shop and DPF was cleaned. All new gaskets and clamps. He had a massive exhaust manifold leak so that was taken care of by me. His turbo also took a #### so that was replaced by me as well while I did the exhaust manifold gaskets. I cleaned his fuel doser injector and installed it with new gaskets while the down pipe was off. Shop didn't reset the doc/dpf so I did that with my insite. I also removed the exhaust back psi sensor and cleaned out the tube and sensor. His IMP sensor was covered in soot so he just bought a new one and also ordered a exhaust back pressure sensor which hasn't been installed yet. When the fan turns on the DOC temperature increases to almost 480F and as soon as the fan shuts off it goes back down to 440F. Obviously it's not reaching the 500F+ for the fuel to start dosing. No exhaust or boost leaks. Here are some of the data I wrote down during the parked regen:
DPF DIFFERENTIAL PRESSURE: 0.1hg
AFTERTREATMENT FUEL PRESSURE: 14.4psi
CRANKCASE PRESSURE: 0.1 inh20
EXHAUST GAS TEMPERATURE: 390-520F (fluctuating.. keeps jumping up and down might be a possible cause? I also saw it jump to 1000F and back down to 300-500F)
EGR DIFFERENTIAL PRESSURE: 0.2 inhg
EGR VALVE POSITION COMMANDED: 0
EGR VALVE POSITION MEASURED: 0
EXHAUST GAS PRESSURE: 94-95 inhg
INTAKE MANIFOLD PRESSURE: 6.0-6.5 inhg
PERCENT LOAD: 0
TURBO ACTUATOR POSITION COMMANDED: 96%
TURBO ACTUATOR POSITION: 96%
DPF SOOT LOAD: NORMAL
COOLANT TEMPERATURE: 209F
DOC INLET: 432F
DPF INLET: 421F
DPF OUTLET: 411F

 

Look on top of pipe between last CAC tube and intake. There will be a M6 allen head round screw in plug. Remove it. Run forced regen. The ECM will sense loss of boost and attempt to compensate with more. See if your regen temps. get to normal. Your DOC inlet is way to low. When you replaced turbo did you calibrate the actuator through Insite?

 

Yeah the actuator was calibrated pre and post install. It's also a brand new oem actuator. I'll try removing the plug. I'm starting to think I have a bad ground some where since the doc/dpf temp sensor grounds are shared with the ambient temp sensor and coolant level sensor.

 

Intake manifold pressure is too low, should be 8 or higher. Exhaust gas pressure is too low, should be about 120 or a bit higher. Turbo isn't working to create enough back pressure to load the engine. This is why the temps spike a bit when the fan comes one because that additional load is enough to increase exhaust temps slightly. Turbo speed should be 40k or higher. It is probably only about 28k. Check for any boost leaks, pressure test your air to air. Also, make sure the EGR diff pressure tubes and ports in the venturi pipe are clear. The egr valve may be leaking excessively and not detected due to plugged egr tubes. If everything checks out, you need to double check that turbo, actuator and maybe redo the install and calibrate procedure. Basically the turbo is what creates the back pressure to create the heat needed for a regen.

 

Thanks. I removed the EGR delta-p and checked the ports while I was diagnosing this issue. They were clear so I reinstalled it back on. During one of the parked regen the delta-p set a out of range on the data monitoring, but hasn't done it since then. If I can remember correctly the turbo speed was reading 38,000-39,000. I wasn't suspecting the new turbo because it was showing 98% for actual & commanded so you would think the turbo is already creating that pressure/heat that it needs too.

 

Most turbos I see are 87-92% Never 96-98 like you are seeing. Is this a genuine Reman Cummins turbo?

 

Yeah purchased through a KW dealer with a new VGT actuator.

 

Maybe double check the part number of the turbo to make sure they gave you the right one. If you have the engine serial number, I can see what it was built with.

 

79366928

I'm going to check the ECM calibrations tomorrow and flash it to the latest if the software right now is old. I don't think this will fix the issue, but it's worth a try. This has been happening for a while. Even prior to his new turbo replacement, the DOC/DPF temps would stay in the 400's and shop did suspect a bad turbo, but he didn't pull the trigger until I took the actuator off and found the actuator itself binding pretty badly and the turbo shaft was binding and not moving freely. When his soot level with the old turbo was high, the regen completed once with the temperatures in the correct range and after that its been the same even after resealing the exhaust manifold, checking the delta-p ports, cleaning sensors & pressure tubes, and replacing the turbo/actuator. The exhaust gas temperature isn't reading correctly its jumping all over the place from 300F to even 1000F and ranging around 400-600F... it doesn't hold steady or climb in small numbers... it drastically dropping and gaining. Does the ISX CM871 even have a exhaust temperature sensor?

 

I show 4955425 NX or 4309076NX for the turbo, and 4034289RX for the actuator. CPL2732.