DTC 81-51, 81-53, 81-55, 81-57: Central Processing Unit (CPU) Internal Circuit Malfunction

WARNING: This page is about a different car, the 2011 Honda Fit, 2010 Honda Fit, and 2009 Honda Fit. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information. (See General Troubleshooting Information ).

Turn the ignition switch to ON (II).
Clear the DTC with the HDS.
Turn the ignition switch to LOCK (0).
Test-drive the vehicle at 19 mph (30 km/h) or more.
NOTE: Drive the vehicle on a straight section of road, not on a lift.
Check for DTCs with the HDS.
Is DTC 81-51, 81-53, 81-55, or 81-57 indicated?

YES - Go to step 6.

NO - Intermittent failure, the system is OK at this time. Refer to intermittent failures troubleshooting (see Intermittent Failures ).
Turn the ignition switch to LOCK (0).
Disconnect the VSA modulator-control unit 36P connector (see step 3 ).
Turn the ignition switch to ON (II).

Measure the voltage between body ground and the appropriate VSA modulator-control unit 36P connector terminals (see table below).

CONNECTOR TERMINAL REFERENCE TABLE

DTC	VSA Modulator-control Unit 36P Connector Terminal
81-51	No. 23
81-53	No. 19
81-55	No. 18
81-57	No. 21

Fig 1: Measuring Voltage Between Body Ground & VSA Modulator-Control Unit 36P Connector Terminals

Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there 0.1 V or more?

YES - Repair short to power in the wire between the appropriate wheel speed sensor and the VSA modulator-control unit.

NO - Go to step 10.

Turn the ignition switch to LOCK (0).
Reconnect the VSA modulator-control unit 36P connector.

Substitute a known-good wheel speed sensor for the appropriate wheel.

CONNECTOR TERMINAL REFERENCE TABLE

DTC	Appropriate Wheel Speed Sensor
81-51	Right-front
81-53	Left-front
81-55	Right-rear
81-57	Left-rear

Test drive the vehicle at 19 mph (30 km/h) or more.
NOTE: Drive the vehicle on the road, not on a lift.
Check for DTCs with the HDS.
Is DTC 81-51, 81-53, 81-55, or 81-57 indicated?

YES - Reinstall the original wheel sensor, then go to step 14.

NO - Replace the original wheel sensor.
Update the VSA modulator-control unit if it does not have the latest software (see VSA MODULATOR-CONTROL UNIT UPDATE ).
Test-drive the vehicle at 19 mph (30 km/h) or more.
NOTE: Drive the vehicle on a straight section of road, not on a lift.
Check for DTCs with the HDS.
Is DTC 81-51, 81-53, 81-55, or 81-57 indicated?

YES - Check for loose terminals in the VSA modulator-control unit 36P connector. If the symptom/indication is still present, replace the VSA modulator-control unit (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ).

NO - If the VSA modulator-control unit was updated, troubleshooting is complete. If any other DTCs are indicated, go to the indicated DTCs troubleshooting.