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EPS 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)
  • If the MIL stays on, or the D indicator blinks at the same time as DTC 21-01 or DTC 21-02 is indicated, troubleshoot the PGM-FI system or A/T model: automatic transmission system, then recheck for DTC 21-01 or DTC 21-02.
  • 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.
  • The ABS indicator may come on during this troubleshoot. If so, clear the DTC related to the ABS.
  1. Turn the ignition switch to LOCK (0).
  1. Connect the HDS to the data link connector (DLC).
  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 EPS DATA LIST with the HDS.
Is 0 km/h (0 mph) indicated?
Go to Step 6 .
NO -
Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the ECM/PCM and the EPS control unit.■
  1. Turn the ignition switch to LOCK (0).
  1. Start the engine and check the tachometer.
Is the tachometer working correctly?
Go to Step 8 .
NO -
  1. Turn the ignition switch to LOCK (0).
  1. Short the SCS line with the HDS.
  1. Disconnect the ECM/PCM connector A (49P) and EPS control unit connector C (16P).
  1. Check for continuity between EPS control unit connector C (16P) terminal and ECM/PCM connector A (49P) terminal individually.
    EPS Control Unit Connector C (16P) Terminal
    ECM/PCM Connector A (49P) Terminal

Is there continuity?
Check for loose terminals in the EPS control unit connectors, 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 ECM/PCM.■