CM870 ghost derate

[Rawze]

(09-21-2022 )ads1 Wrote:  Update: I’ve acquired Insite and it’s showing me something I could not see with my generic scanner. Turbo compressor Inlet Air Temp is at 59 degrees F and I replaced the sensor and same thing. Also, turbo compressor outlet air temp (calculated) shows 406 degrees F even when truck is cold. Does anyone know what could cause this? Is it possible someone has “egr deleted” this truck? I can perform a egr test and the valve opens and closes fine.

those sound like symptoms of a typical bad delete perhaps.

Start by taking the truck to the OEM stealers$it and have the correct program flashed into it that belongs to the engine according to its ser#. A CM870 will not shut down if it has been deleted.. it will only have a CEL light on + a boost derate but not a power derate.



Also.. you may simply be chasing a ghost any ways. There may actually be noting wrong, as some programs for the ISX are set to only give you full power/torque for a short period of time (30 seconds to 1 minute).. and then back itself off. It is called the 'Smart Torque" feature, and many engines came with this setting permanently turned on.

if there is an actual derate then you need to watch the life fuel flow (mg/stroke) in Insite + the engine state parameter, plus the turbo rpm + boost pressure and see how it fairs out as it starts falling off.

Also: the ISX will hold fuel back if the boost is wonky .. and those CM870's are notorious for wonky boost .. especially if it has a bad delete program in it.. or if the boost controller is starting to go bad.. or if the turbo arm is starting to hang up on it.

Also, If the EGR is still active on it then it could be the EGR valve acting up, causing power loss.


Also, if the truck is old then the exhaust back-pressure sensor siccuit might be clogged up that runs thru the thermostat housing. They are notorious for this and it makes the turbo act wonky... leading to efficiency losses and power issues.


-=== Ie.. take you pick and start working thru the list.