DTC Troubleshooting: 21-01, 21-02
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 detecting condition of the DTC 21-01 or DTC 21-02.
  1. Turn the ignition switch to LOCK (0).
  1. Raise the vehicle, and support it with safety stands in the proper locations, and allow all four wheels to rotate freely.
  1. Connect the HDS to the data link connector (DLC).
  1. Turn off VSA by using the VSA OFF switch.
  1. Start the engine, then run the vehicle in the 4th gear (M/T), or D position (A/T).
  1. Check the VEHICLE SPEED in the DATA LIST with the HDS.
Is vehicle speed indicated?
YES -
Intermittent failure, the system is OK at this time.■
NO -
Go to Step 7 .
  1. Check for DTCs in the PGM-FI system (M/T) or A/T system (A/T) with the HDS.
Is DTC P0720 (M/T), P0721 (A/T), P0722 (A/T), or P0723 (A/T) indicated?
YES -
Troubleshoot the indicated DTC(s).■
NO -
Go to Step 8 .
  1. Start the engine and check the tachometer.
Is the tachometer working correctly?
YES -
Go to Step 10 .
NO -
Go to Step 9 .
  1. Check for DTCs in the gauge control module with the HDS.
Is DTC indicated?
YES -
Troubleshoot the indicated DTC(s).■
NO -
Update the ECM/PCM if it does not have the latest software: R20A3 engine model, K24Z3 engine model, or substitute a known-good ECM/PCM: R20A3 engine model, K24Z3 engine model, then go to Step 4 and recheck. If the ECM/PCM was updated and DTCs are not indicated, troubleshooting is complete. If the ECM/PCM was substituted and DTCs are not indicated, replace the original ECM/PCM: R20A3 engine model, K24Z3 engine model. ■
  1. Turn the ignition switch to LOCK (0).
  1. Short the SCS line with the HDS.
  1. Disconnect the EPS control unit connector D (28P) and ECM/PCM connector A (44P) or ECM/PCM connector A (49P).
  1. Check for continuity between EPS control unit connector D (28P) terminal No. 1 and ECM/PCM connector A (44P) terminal No. 36 *1 or ECM/PCM connector A (49P) terminal No. 3 *2 .
    *1: R20A3 engine model
    *2: K24Z3 engine model
Is there continuity?
YES -
Go to Step 14 .
NO -
Repair open in the wire between the EPS control unit and the ECM/PCM.■

R20A3 engine model
K24Z3 engine model