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Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.
DTC B2278 DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 INSPECT TORQUE SENSOR USING WDS OR EQUIVALENT 
  • Turn the ignition switch off.
  • Connect the WDS or equivalent to the DLC-2.
  • Turn the ignition switch to the ON position (engine OFF).
  • Access TRQ_SENS PID.
  • Verify that the data monitor value changes when the steering wheel is turned.

    Left: 0- -32 NM 

    Right: 0-31.75 NM 

  • Do the torque sensor signal values change in the same way?
 Yes Malfunction may be temporary. Go to step 7.
No Go to the next step.
2 INSPECT WHETHER MALFUNCTION IS CAUSED BY POOR CONNECTION OF EPS CONTROL MODULE OR PIN DEFORMATION 
  • Turn the ignition switch off.
  • Inspect connection of the EPS control module and wiring harness.
  • Disconnect the EPS control module connector.
  • Inspect whether malfunction is caused by bent or poorly connected EPS control module connector pin.
  • Are the connector connection, connector pins, and wiring harness normal?
 Yes Go to the next step.
No Repair or replace the faulty connector wiring harness, then go to Step 7.
3 INSPECT TORQUE SENSOR CIRCUIT FOR OPEN CIRCUIT 
  • Inspect for continuity between the EPS control module terminals and torque sensor terminals.
    • EPS control module terminal 3A-torque sensor terminal A
    • EPS control module terminal 3B-torque sensor terminal B
    • EPS control module terminal 3C-torque sensor terminal C
  • Is there continuity?
 Yes Go to the next step.
No Repair or replace the wiring harness for open circuit between the EPS control module and torque sensor, then go to Step 7.
4 INSPECT TORQUE SENSOR CIRCUIT FOR SHORT TO POWER 
  • Measure the voltage between the torque sensor terminals and ground.
    • Torque sensor terminal A-ground
    • Torque sensor terminal B-ground
    • Torque sensor terminal C-ground
  • Is there any B+?
 Yes Repair or replace the wiring harness for short to power between the EPS control module and torque sensor, then go to Step 7.
No Go to the next step.
5 INSPECT TORQUE SENSOR CIRCUIT FOR SHORT TO GROUND 
  • Inspect for continuity between the torque sensor terminals and ground.
    • Torque sensor terminal A-ground
    • Torque sensor terminal B-ground
    • Torque sensor terminal C-ground
  • Is there continuity?
 Yes Repair or replace the wiring harness for short to ground between the EPS control module and torque sensor, then go to the next step.
No Go to the next step.
6 INSPECT TORQUE SENSOR 
  • Turn the ignition switch off.
  • Disconnect the torque sensor connector.
  • Measure the resistance between the torque sensor terminals.
    • Terminals A-B
    • Terminals B-C

      Resistance: 12-15 ohms 

  • Is the torque sensor normal?
 Yes Go to the next step.
No Replace the steering gear and linkage, then go to Step 7.
(See STEERING GEAR AND LINKAGE REMOVAL/INSTALLATION .)
7 VERIFY TROUBLESHOOTING COMPLETED 
  • Make sure to reconnect all disconnected connectors.
  • Clear the DTC from the memory.

    (See CLEARING DTCS PROCEDURE .)

  • Turn the ignition switch off.
  • Start the engine.
  • Is the same DTC present?
 Yes Replace the EPS control module, then go to the next step.
(See EPS CONTROL MODULE REMOVAL/INSTALLATION .)
No Go to the next step.
8 VERIFY AFTER REPAIR PROCEDURE 
  • Are any other DTCs present?
 Yes Go to the applicable DTC inspection.
(See DTC TABLE .)
No DTC troubleshooting completed.
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