Richard B Posted May 4, 2022 Share Posted May 4, 2022 Good afternoon. First time posting and in need of your help. I have a 2012 Mack Granite with a Cummins Engine. I have the lighting bolt on with 4 Codes. Engine Protection Torque Derate which we all know. AFT 1 DEF Line Heater 1 Circuit OEM Code 3258 SPN 4340 Current Below Normal Or open Circuit AFT 1 DEF Line Heater 2 Circuit OEM Code 3261 SPN 4342 Current Below Normal Or open Circuit AFT 1 DEF Line Heater 3 Circuit OEM Code 3425 SPN 4344 Current Below Normal Or open Circuit So far what I have checked. All heater lines were ohm and came back at 5.00 no opens. the harness was taken out and ever wire ohm back to the 86 pin connector on the Bosch Controller. All wires are good. circuit Breaker 20amp to supply def heater lines has 12v in fuse panel. The Bosch Controller has 4 12v lines in the smaller connector. the part that confused me was I pulled the 20amp breaker out and didn't loose any of the 12v pins. Don't know which pin supplies the 12v to the heaters. also are the heater relay built into the controller. this controller is mounted under the cab and not on the DEF tank.I don't have the Pinout for the connectors. Im using a snap-on Ultra pro link. if you erase the codes the come right back. they seem to be a hard fault. If you run the test on the heater lines it fails. Im at a loss and need some help. 1 Quote Link to comment Share on other sites More sharing options...
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