56-31

SRS DTC Troubleshooting: 56-31

DTC 56-31: Lost Communication With the ECM/PCM (PGM-FI system)

NOTE:

- Before doing this troubleshooting procedure, review SRS Precautions and Procedures, Technician Safety Information General Troubleshooting Information, Initial Inspection and Diagnostic Overview and Battery Terminal Disconnection and Reconnection. Procedures

- Check for any F-CAN and B-CAN communication DTCs, and troubleshoot those DTCs before doing this troubleshooting procedure.

- 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, SRS Unit Update and retest.

1. Clear the DTC memory. Initial Inspection and Diagnostic Overview

2. Turn the ignition switch to ON (II), then wait for 10 seconds.

3. Read the DTC. Initial Inspection and Diagnostic Overview

Is DTC 56-31 indicated?
YES - Go to step 4.

NO - Intermittent failure, the system is OK at this time. Go to Troubleshooting Intermittent Failures. Initial Inspection and Diagnostic Overview If another DTC is indicated, troubleshoot the DTC.


4. Turn the ignition switch to LOCK (0).

5. Turn the ignition switch to ON (II), and see if the malfunction indicator lamp (MIL) comes on and stays on.

Does the MIL stay on?
YES - Go to the MIL Circuit Troubleshooting. MIL Circuit Troubleshooting

NO - Go to step 6.


6. Turn the ignition switch to LOCK (0).

7. Disconnect the negative cable from the battery, then wait at least 3 minutes.

8. Disconnect SRS unit connector A (39P) from the SRS unit. Technician Safety Information

9. Disconnect ECM/PCM connector A (49P) from the ECM/PCM. Service and Repair

10. Measure the resistance between SRS unit connector A (39P) terminals No. 16 and No. 17, and ECM/PCM connector A (49P) terminals No. 4 and No. 3, individually. There should be less than 1.0 Ohms.

Is the resistance as specified?
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. SRS Unit Replacement

NO - Open in the left engine compartment wire harness or the dashboard wire harness; replace the faulty harness, then clear the DTC.