Q: Trouble code P0607 Engine Control Module & P0138 Oxygen Sensor Circuit

Replacing an engine control module should never be a first step. There are a number of other problems that can give a PO607 trouble code. First the battery voltage should be checked, and if the engine is running, the charging system voltage should also be checked. All of the ground connections should also be inspected. By testing the voltages at the pins on the ECU connector you can determine if the connections are in good condition.

The PO138 code could also be an electrical harness problem in that a damaged sensor harness could shunt heater voltage to the sensor signal wire. So before you spend money on expensive parts that are not returnable, you should give the electrical harness a very thorough inspection. Look for damaged connectors or places where the wires have been rubbed through by contacting moving parts.

If you don’t want to take this on, YourMechanic can send a qualified technician to your home or office to properly diagnose your car’s Check Engine Light and recommend a solution.