We had a customer come in to us today complaining that the dash lights are calling for the driver to do a parked DPF regeneration but the truck wont let him do it. The driver places the truck on a surface away from potential fire hazards, sets the park brake, insures the cruise and engine brake switches are in the off position then holds the “Regen” button like hes supposed to… problem is, the light on the button just flashes and nothing happens.
In this instance, the driver did everything correctly but the truck wasnt responding. Usually when the “Regen” button flashes, its an indicator to the driver that a condition isn’t met. The ECM runs numerous checks on the condition of switches it requires to initiate a parked Regen. Cruise control, Engine Brakes, Park brake, clutch pedal, throttle pedal, brake pedal, transmission neutral switch and DPF soot load need to be working and reading the condition the ECM requires to initiate the process. If anyone of these conditions are not met, the truck will not cooperate.
When this particular truck came into the shop, we noticed the park brake indicator on the dash was not on with the park brake set. step number one; hook up the computer and check to see what condition the ECM is reading, this rules out a burnt out dash bulb. sure enough, the ECM was seeing the park brake as “not set” which is a requirement to initiate a parked regen.
at this point, were hot on the heels of the problem.
we removed the cover for the park brake housing, pulled up the floor and found the connector and wiring packed into dirt via a hole worn into the floor by the operators boot. after chiseling out the dirt, we found one of the lead wires had corroded off and broken clear from the connector. We removed the magnetic switch, tested it, then rewired a proper connection. Success! the park brake light is now on. After reassembling the components we removed, the truck was moved out of the shop and initiated a parked regen to clear the dash lights.
A simple thing like the ECM not seeing the park brakes position can cause a lot of expensive down time. Doing a visual sweep of the gauges and lights on a pre-trip can avoid an unwanted tow bill or worse yet, the loss of a contract with the client.
