DTC 56-25: Lost Communication With the Gauge Control Module

Before doing this troubleshooting procedure, find out if the vehicle was in a collision. If so, verify that all the required components were replaced with new components, of the correct part number, and that they were properly installed (see COMPONENT REPLACEMENT/INSPECTION AFTER DEPLOYMENT ).
Before doing this troubleshooting procedure, review SRS Precautions and Procedures (see PRECAUTIONS AND PROCEDURES ), General Troubleshooting Information (see DTC (DIAGNOSTIC TROUBLE CODES) ), and 12 Volt Battery Terminal Disconnection and Reconnection (see 12 VOLT BATTERY TERMINAL DISCONNECTION AND RECONNECTION ).
Before replacing the SRS unit, check the SRS unit software version with the HDS. If the software version is not the latest, update the SRS unit software (see SRS UNIT UPDATE ) and retest.

Check for any F-CAN and B-CAN communication DTCs with the HDS.
Are there any communication DTCs?

YES - Go to the appropriate DTC troubleshooting.

NO - Go to 2
Release the parking brake, turn the ignition switch to ON (II), and see if the brake system indicator comes on for 2 seconds and then goes off.
Does the brake system indicator come on and then go off after 2 second?

YES - Go to 3

NO - Faulty gauge control module. Do the gauge control module self-diagnostic function (see SELF-DIAGNOSTIC FUNCTION ), and retest. If the gauge control module fails the self-diagnosis, replace the gauge control module (see GAUGE CONTROL MODULE REPLACEMENT ), then clear the DTC, and retest. If the DTC is still present, replace the SRS unit (see SRS UNIT REPLACEMENT ).
Clear the DTCs with the HDS (see HOW TO CLEAR DTCS ).
Turn the ignition switch to ON (II), then wait for 10 seconds.
Check for DTCs with the HDS (see HOW TO CLEAR DTCS ).
Is DTC 56-25 indicated?

YES - Go to 6

NO - Intermittent failure, the system is OK at this time. Go to Troubleshooting Intermittent Failures (see TROUBLESHOOTING INTERMITTENT FAILURES ). If another DTC is indicated, troubleshoot the DTC.
Turn the ignition switch to LOCK (0).
Disconnect the negative cable from the 12 volt battery, then wait at least 3 minutes.
Disconnect SRS unit connector A (39P) from the SRS unit (see 11).
Disconnect gauge control module 32P connector (see GAUGE CONTROL MODULE REPLACEMENT ).
Check for continuity between SRS unit connector A (39P) terminal No. 6 and gauge control module 32P connector terminal No. 19, and between SRS unit connector A (39P) terminal No. 7 and gauge control module 32P connector terminal No. 20.

Fig 1: Checking For Continuity Between SRS Unit Connector A (39P) Terminal No. 6 And Gauge Control Module 32P Connector Terminal No. 19, And Between SRS Unit Connector A (39P) Terminal No. 7 And Gauge Control Module 32P Connector Terminal No. 20
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Faulty SRS unit or poor connection at SRS unit connector A (39P) and the SRS unit. Check the connection between the connector and the SRS unit. If the connection is OK, replace the SRS unit (see SRS UNIT REPLACEMENT ). If the DTC does not clear, replace the dashboard wire harness.

NO - Open in the harness between SRS unit connector A (39P) terminal No. 6 and gauge control module 32P connector terminal No. 19, or between the SRS unit connector A (39P) terminal No. 7 and gauge control module 32P connector terminal No. 20; replace the dashboard wire harness, then clear the DTC.