DTC 21-01

DTC 21-01: Excessive change of the Vehicle Speed Signal (Regular diagnosis)

DTC 21-02: Comparison between the Vehicle Speed and the Engine Speed Signal (Regular diagnosis)

NOTE: If the MIL indicator is on, troubleshoot the PGM-FI system first. Even though the system is operating normally, the EPS indicator will come on caused by the detecting condition of DTC 21-01 or DTC 21-02.

1. Turn the ignition switch OFF.
2. Raise the vehicle, and support it with safety stands in the proper locations, and allow all wheels to rotate freely.
3. Connect the HDS to the data link connector (DLC).
4. Start the engine, test the vehicle in the D position.
5. Check the VEL in the DATA LIST with the HDS.
Is the vehicle speed indicated?
YES - The system is OK at this time.
NO - Go to step 6.

6. Check for DTCs in the A/T system with the HDS.
Is DTC P0721, or P0722 indicated?
YES - Troubleshoot the indicated DTC.
NO - Go to step 7.

7. Start the engine and check the tachometer.
Is the tachometer working correctly?
YES - Go to step 8.
NO - Troubleshoot the gauge control module (tach).

8. Turn the ignition switch OFF.
9. Disconnect PCM connector A (44P) and EPS control unit connector D (28P).





10. Check for continuity between EPS control unit connector D (28P) terminals No. 1 and PCM connector A (44P) terminals No. 36.
Is there continuity?
YES - Go to step 11.
NO - Repair open in the wire between the EPS control unit and the PCM.





11. Check for continuity between EPS control unit connector D (28P) terminals No. 15 and PCM connector A (44P) terminals No. 37.
Is there continuity?
YES - Check for loose terminals in the EPS control unit D (28P) connector, and repair if necessary. If no poor connections are found, replace the EPS control unit.
NO - Repair open in the wire between the EPS control unit and the PCM.