I had this issue a couple weeks ago. The problem ended being a stuck open thermostat and it wouldn't allow the engine to get up to operating temp. This motor can't do passive regens if its not at operating temp and it would turn on the DPF light.
It could be the maintenance required light. It is set to go on at set intervals. there is a reset procedure on our buses. I will try to look it up today. Also some Maintenance required lights can only be shut of by a dealer. I believe the ESW DPF is that way.
Thanks for the tips guys. This morning our head mechanic called the IC support line. They got them to change one of the throttle control settings to "In Cab Throttle control" as opposed to "Remote throttle control" (which it was currently setup for. We don't use remote throttle control) through the laptop. This service code was number 45001 on their program (servicemax I believe). As well, there was a short in the turbo electrical wiring that would cause a code for excessive back pressure. Everything is fixed up now, and works great.
Thanks again for the suggestions.
Pic courtesy of: "schoolbusdriver.org"
Edited by - 1983ChevroletWayne on 03/08/2014 05:39:37 AM