ECT4 Check SIGRTN Circuit

- Key OFF.

- Disconnect the engine coolant temperature sensor connector.

- Install Rotunda Breakout Box 007-00033, or equivalent with Rotunda Breakout Box Adapter 007-00053 (leave the PCM disconnected).

- Measure the resistance between SIGRTN BOB Pin 46 and the SIGRTN wire at the engine coolant temperature sensor connector.

- Is the resistance less than 5 ohms?

YES -- SERVICE the ECT wire to PCM.

NO -- SERVICE the SIGRTN wire to the PCM.