SIR Diagnostic System Check

SIR Diagnostic System Check:

CAUTION: To avoid deployment when troubleshooting the SIR system, do not use electrical test equipment such as a battery powered or AC powered voltmeter, ohmmeter, etc., or any type of electrical equipment other than that specified. Do not use a non-powered probe type tester. Instructions must be followed carefully, otherwise personal injury may result.

CIRCUIT DESCRIPTION
When the ignition switch is first turned "ON," "Ignition 1" voltage is applied from the "AIR BAG" fuse to the DERM at the "Ignition 1" input terminals "A9" and "A10" and from the "IGN" fuse 1D to the DERM at the "Redundant Indicator Ignition 1" input terminal "B2." The DERM responds by flashing the "INFLATABLE RESTRAINT" warning lamp 7 times while performing tests on the SIR system.

When the engine is being cranked, "Ignition 1" voltage is applied from the "CRANK" fuse to the DERM at the "Crank" input terminal "B10." The DERM responds by grounding the "SIR Indicator" output terminal "B1" until "Ignition 1" voltage is removed from the "Crank" input. This results in the "INFLATABLE RESTRAINT" warning lamp being "ON" steady during cranking.

After cranking the DERM will flash the "INFLATABLE RESTRAINT" warning lamp 6 times and perform tests on the SIR system.

NOTES ON SYSTEM CHECK CHART:
1. The "INFLATABLE RESTRAINT" warning lamp should flash 7 times after ignition is first turned "ON."
2. The "INFLATABLE RESTRAINT" warning lamp should remain "ON" steady during cranking.
3. After cranking, the "INFLATABLE RESTRAINT" warning lamp should flash 6 times then go "OFF."
4. This test checks for the proper operation of the "Serial Data" line. This test will also determine whether history diagnostic trouble codes are stored and, if so, identify them.
5. When the "INFLATABLE RESTRAINT" warning lamp flashes 4 times during "Bulb Check" this indicates a malfunction in the redundant lamp driver circuitry. These malfunctions are diagnosed by DTC 62 Test. DTC 62
6. Improper operation of the "INFLATABLE RESTRAINT" warning lamp is indicated. This test differentiates a warning lamp stays "ON" condition from a warning lamp does not come "ON" condition.
7. This test checks for proper operation of the "Serial Data" line. This test will also identify the stored diagnostic trouble codes and whether they are current or history.

DIAGNOSTIC AIDS:
The order in which diagnostic trouble codes are diagnosed is very important. Failure to diagnose the diagnostic trouble codes in the order specified may result in extended diagnostic time, incorrect diagnosis and incorrect parts replacement.