Electrical Power Steering (EPS) Signal Circuit Troubleshooting

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2005 Honda S2000, 2004 Honda S2000, 2003 Honda S2000, 2002 Honda S2000, and 2001 Honda S2000. However, it is still accessible from the selected car via links, so may be relevant.

Turn the ignition switch ON (II).
Measure voltage between ECM connector terminals A26 and B20.

Fig 1: Measuring Voltage Between ECM Connector Terminals A26 And B20
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Go to step 6.
2. NO - Go to step 3.
Start the engine.
Turn the steering wheel to the full lock position.
Measure voltage between ECM connector terminals A26 and B20.
Is there battery voltage briefly?
1. YES - The EPS signal is OK.
2. NO - Go to step 10.
Turn the ignition switch OFF.
Disconnect the EPS control unit 14P connector.
Turn the ignition switch ON (II).
Measure voltage between EPS control unit 14P connector terminal No. 13 and body ground.

Fig 2: Measuring Voltage Between EPS Control Unit 14P Connector Terminal No. 13 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Substitute a known-good EPS control unit and recheck.
2. NO - Repair open in the wire between the ECM (A26) and the EPS control unit.
Turn the ignition switch OFF.
Disconnect the EPS valve 14P connector.
Turn the ignition switch ON (II).
Measure voltage between EPS control unit 14P connector terminal No. 13 and body ground.

Fig 3: Measuring Voltage Between EPS Control Unit 14P Connector Terminal No. 13 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Substitute a known-good EPS control unit and recheck.
2. NO - Go to step 14.
Turn the ignition switch OFF.
Disconnect ECM connector A (32P).
Check for continuity between body ground and ECM connector terminal A26.

Fig 4: Checking Continuity Between Body Ground And ECM Connector Terminal A26
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Repair short in the wire between the ECM (A26) and the EPS control unit.
2. NO - Substitute a known-good ECM (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES ) and recheck. If the voltage is now normal, replace the original ECM (see ECM REPLACEMENT ).