56-21

SRS DTC Troubleshooting: 56-21

DTC 56-21:

Lost Communication with the PCM (PGM-FI system)

NOTE: Before doing this troubleshooting procedure, review SRS Precautions and Procedures Service and Repair, General Troubleshooting Information Reading and Clearing Diagnostic Trouble Codes, and Battery Terminal Disconnection and Reconnection Procedures.

1. Turn the ignition switch to ON (II), and see if the other indicators come on (brake system, etc.).

Do the other indicators come on?

YES -

Go to step 2.

NO -

Go to the gauge control module Self-diagnostic Function Initial Inspection and Diagnostic Overview.�

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

3. Turn the ignition switch ON (II), and see if the MIL come on.

Does the MIL come on?

YES -

Go to step 4.

NO -

Go to the PGM-FI System troubleshooting MIL Circuit Troubleshooting.�

4. Clear the DTC memory Reading and Clearing Diagnostic Trouble Codes.

5. Turn the ignition switch to LOCK (0) and wait for 10 seconds.

6. Turn the ignition switch to ON (II) and wait for 10 seconds.

7. Read the DTC Reading and Clearing Diagnostic Trouble Codes.

Does the SRS indicator stay on, and is DTC 56-21 indicated?

YES -

Go to step 8.

NO -

Intermittent failure, system is OK at this time. Go to Troubleshooting Intermittent Failures Reading and Clearing Diagnostic Trouble Codes. If another DTC is indicated, troubleshoot the DTC.�

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

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

10. Disconnect SRS unit connector A (28P) from the SRS unit Service and Repair.

11. Jump the SCS line with the HDS Initial Inspection and Diagnostic Overview.

12. Disconnect PCM connector A (49P) from the PCM.

13. Check for continuity between SRS unit connector A (39P) terminal No. 11 and PCM connector A (49P) terminal No. 48, and between SRS unit connector A (39P) terminal No. 12 and PCM connector A (49P) terminal No. 49.





Is there continuity?

YES -

Faulty SRS unit or poor connection at SRS unit connector A (28P) and the SRS unit. Check the connection; if the connection is OK, replace the SRS unit SRS Unit Replacement.�

NO -

Open in the dashboard wire harness or engine compartment wire harness, connector E (14P), and connector (13P) at the passenger's under-dash fuse/relay box Passenger's Under-dash Fuse/Relay Box Connector Locations. If the connections are OK, replace the faulty harness or component, then clear the DTC.�