Diagnostic Instructions
Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)
Diagnostic Instructions
The symptom chart can be used to help locate Supplemental Restraint System (SRS) concerns if no DTCs are retrieved and the listed symptoms are observed. Whether or not the listed symptoms are observed, always carry out the following:
1. Run the Self Test to determine what on-demand and CMDTCs are being sensed by the Restraints Control Module (RCM)/Occupant Classification System Module (OCSM).
2. Retrieve all SRS DTCs and fault PIDs stored in the RCM and OCSM memory.
3. If on-demand DTCs are different than CMDTCs, always repair the on-demand DTCs first.
A DTC can indicate several concerns. The DTCs are to assist in system diagnosis and are not to be considered definitive. Always refer to the pinpoint test corresponding to the DTC to determine where the concern lies and to repair the concern correctly.
Self Test/Continuous Memory and Clear DTCs
During vehicle operation, the Restraints Control Module (RCM)/Occupant Classification System Module (OCSM) will detect and store both intermittent and hard failure DTCs in non-volatile memory. The DTC strategy employed by the RCM/OCSM incorporates a time-out scheme for determining when a concern exists in the system. This requires a concern to exist for up to one minute in the system before the RCM/OCSM will detect it. For the RCM/OCSM to determine that a concern no longer exists, the concern must be absent for up to one minute. The actual detection time-outs vary with each DTC and module. DTCs can be retrieved with a scan tool using the Self Test option. All DTCs stored in the RCM and OCSM will be displayed on the scan tool along with a brief description of the DTC. If no DTCs are present, the scan tool will display a SYSTEM PASSED message. This option can also be used to clear DTCs from the RCM and OCSM memory, as long as the concern no longer exists.
Once 75 hours of operation have been recorded by the RCM and 128 ignition cycles have been recorded by the OCSM since the concern was last detected, all CMDTCs will automatically be removed from memory.
Lamp Fault Codes (LFCs)
When the Restraints Control Module (RCM) detects a system fault, it will send a message to Instrument Cluster (IC) module to flash a coded sequence which is called a Lamp Fault Code (LFC) on the air bag warning indicator. The code is 2 digits. The first digit is flashed with a 0.5-second interval between pulses. There is a 2-second pause before the second digit is flashed, which also has a 0.5-second interval between pulses. There is a 5-second pause between each display of an LFC.
Each LFC is flashed 3 times after which the air bag indictor will remain lit for the remainder of the ignition-on cycle. If there are multiple LFCs, each LFC will flash in order of priority.
Bit-Mapped DTCs
Many of the continuous memory and on-demand DTCs that can be present in the Restraints Control Module (RCM)/Occupant Classification System Module (OCSM) provide general fault information and require accessing the bit-mapped PIDs (fault PIDs) to identify the specific concern. DTCs that use fault PIDs are conceptually different from conventional DTCs.
Conventional DTCs identify a specific concern for a given component and point to a particular diagnostic path. In the diagnostic path, PIDs are sometimes used to determine the root cause.
DTCs that use fault PIDs do not identify the specific concern. The DTC identifies the component(s) or type of components in which the concern exists. The next level, fault PIDs, identifies the specific device and fault condition. Fault PIDs are available for both on-demand (active) and continuous memory (historic) DTCs. Those associated PIDs are an extension of the information provided by the DTC and are identified by the same DTC number. Using both DTC and the fault PID is necessary to define the specific fault present (in the same manner as normal DTCs).
A scan tool must be used to view DTCs and their fault PIDs. Once a scan tool has retrieved a DTC, use the scan tool to view the fault PIDs. Viewing the fault PIDs must be carried out to identify the specific concern that is present. When the viewing of fault PIDs has been carried out, the scan tool can display the PIDs associated with that DTC, including the status or state that exists (on-demand DTC) or existed (continuous memory DTC). Refer to the manufacturer's instructions for the scan tool being used on how to view fault PIDs.
Prove Out Procedure
Turn the ignition switch from the OFF to the ON position and visually monitor the air bag warning indicator with all Supplemental Restraint System (SRS) components connected. The Instrument Cluster (IC) module will illuminate the air bag warning indicator continuously for approximately 6 seconds and then turn off. If an SRS fault is present, the air bag warning indicator will:
- fail to light.
- remain lit continuously.
- flash.
The air bag warning indicator may not illuminate until approximately 30 seconds after the ignition switch has been turned from the OFF to the ON position. This is the time required for the Restraints Control Module (RCM) to complete the testing of the SRS. If the air bag warning indicator is inoperative and an SRS fault exists, a chime will sound in a pattern of 5 sets of 5 beeps. If this occurs, the air bag warning indicator will need to be repaired before diagnosis can continue.