DEF heater circuit codes keep returning
Truck came in derate with no communication to aftertreatment module. load tested power and ground circuits to module and tested communication circuits between ECM and aftertreatment module. module was badly corroded so we replaced it with a new module from freightliner. reflashed to take it out of derate. communication was restored everything worked fine for a short period of time. then codes 3258 and 3261 set for DEF line heaters 1 and 2 circuit OPEN. followed the flow chart and unplugged the #2 DEF heater and shorted the pins together with a jumper wire and it set code 3237 for heater circuit short to power. so replaced all 3 DEF lines. Codes 3258 and 3261 returned. installed new heater relay, load tested the supply circuit, tested for a short to ground, checked pin fit at module, inline connector and at the heaters themselves. code still comes back. i back probed the heater return pin at the after treatment module and i have battery voltage when the key is on. at this point I feel like I have a bad new module.
If you short the lines together and get short to power fault wouldn’t that indicate everything to the heaters is ok and the heaters themselves need replaced. Did you ohm the heaters to make sure they arnt open.
Yes thats what the service manual said. We’re put new lines on it and no change.
Oh when you said replaced the lines I thought you meant the wires to the heaters.
If you ohm test from module in and back you might be ok I would consider loading the circuit and checking amp draw. Are you using cummins insite?
Like ground a head lamp and power it through the heater circuit? Yes we’re using insite.