P0720

DTC P0720: Problem in Countershaft Speed Sensor Circuit

NOTE: Record all freeze data before you troubleshoot.

1. Check the countershaft speed sensor installation.
Is the countershaft speed sensor installed properly?
YES - Go to step 2.
NO - Reinstall and recheck.
2. Disconnect the 2P connector from the countershaft speed sensor.





3. GMeasure countershaft speed sensor resistance at the sensor connector.
Is the resistance 400 - 600 ohms?
YES - Go to step 4.
NO - Replace the countershaft speed sensor.
4. Disconnect the D (16P) connector from the PCM.





5. Check for continuity between body ground and the D10 terminal and D16 terminal individually.
Is there continuity?
YES - Repair short to ground in the wires between the D10 and D16 terminals and the countershaft speed sensor.
NO - Go to step 6.
6. Connect the countershaft speed sensor connector.





7. Measure the resistance between the D10 and D16 terminals.
GIs the resistance 400 - 600 ohms?
YES - Check for loose terminal fit in the PCM connectors. If necessary, substitute a known-good PCM and recheck.
NO - Repair loose terminal or open in the wires between the D10 and D16 terminals and the countershaft speed sensor.