Diagnostic Instructions
Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)
Diagnostic Instructions
The symptom chart can be used to help locate 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. Retrieve all DTCs stored in the RCM memory and OCSM memory. Refer to Retrieve/Clear Continuous DTCs.
2. Run the on-demand Self Test to determine what DTCs are currently being sensed by the RCM and OCSM.
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/On-Demand
The on-demand Self Test option is used to verify that no electrical concerns exist with the SRS. Upon entering the self-test, the RCM/OCSM will make an electrical check of each electrical component in the system. If a concern is detected, a DTC is displayed on the scan tool with a brief description of the DTC. The self-test should always be run after any repair to verify that the repair was successful.
Self Test/Continuous Memory and Clear DTCs
During vehicle operation, the RCM and OCSM will detect and store both intermittent and hard failure DTCs in non-volatile memory. The DTC strategy employed by the RCM 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 will detect it. For the RCM 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. 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 since the concern was last detected, all RCM CMDTCs will be automatically removed from memory.
Once 128 ignition cycles have been recorded by the OCSM since the concern was last detected, all OCSM continuous memory DTCs will be automatically removed from memory.
DataLogger PID/Data
The DataLogger PID/Data option allows the scan tool operator to read the state of several PIDs to aid in diagnosing the system. PIDs are real time measurements of parameters, such as voltages and resistances, calculated by the RCM sent to the scan tool for display. Many of the PIDs supported by the modules are calculated periodically and are, therefore, not true real time readings.
To retrieve PIDs, follow these steps:
1. Connect the scan tool to the DLC.
2. Turn the ignition to the ON position.
3. Follow the manufacturer's instructions for the scan tool being used.
4. Select DataLogger.
5. Select RCM or OCSM.
Active Commands
Instrument Cluster (IC) module
These commands allow the technician to verify the operation of IC module components and subsystems.
Occupant Classification Sensor (OCS) System Reset
The Occupant Classification Sensor (OCS) System Reset active command sets the zero set point or rezeros the OCS system. Refer to Occupant Classification Sensor (OCS) System Reset Programming and Relearning.
Lamp Fault Codes (LFCs)
This vehicle supports LFCs only when the RCM is in plant mode. A new RCM installed in a vehicle will be in plant mode until:
- Programmable Module Installation (PMI) has been carried out.
- the RCM sees a fault-free SRS (no DTCs present).
If a LFC is present after completing PMI, a fault is present in the SRS and on-demand DTCs must be retrieved and diagnosed.
Diagnosing Customer Concerns With On-Demand DTCs
NOTE: Most SRS diagnostic procedures will require depowering and repowering of the SRS. Depowering and repowering requires disconnecting of the battery and removal of the RCM fuse. This reduces the risk of accidental deployment of SRS components while diagnostic procedures are being carried out.
If the air bag warning indicator is reported ON by the customer when the vehicle comes in for service, connect the scan tool and follow the Diagnostic Instruction procedures to identify the concern.
Once the DTC is known, read the Normal Operation of the pinpoint test for the DTC involved.
Using the scan tool with the use of PIDs and active command(s) may be of assistance in diagnosing the concern.
- Follow the depowering procedure as directed.
- Determine the location of components involved in creating the DTC.
- Carry out a thorough visual inspection of:
- components.
- connectors.
- splices and wiring harnesses.
- insulation on conductors.
Diagnosing Customer Concerns With Continuous Memory DTCs
If an air bag warning indicator ON is reported by the customer but is not present when the vehicle comes in for service, follow the Diagnostic Instruction procedures to identify the intermittent DTC.
Once the DTC is known, read the Normal Operation of the pinpoint test for the DTC involved.
- Follow the depowering procedure as directed.
- Determine the location of components involved in creating the DTC.
- Carry out a thorough visual inspection of:
- components.
- connectors.
- splices and wiring harnesses.
- insulation on conductors.
Refer to the Normal Operations of the pinpoint test for the DTC involved, which lists the common concerns that relate to the DTC. Concerns are listed according to priority.
Bit-Mapped DTCs
Many of the continuous memory and on-demand DTCs that can be present in the RCM provide general fault information and require accessing the associated 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 do).
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 Diagnostic Trouble Code (CMDTC)). 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 monitor the air bag indicator with all SRS components connected. The air bag indicator will light continuously for approximately 6 seconds and then turn off. If an SRS fault is present, the air bag indicator will:
- fail to light.
- remain lit continuously.
- flash at a 5Hz rate RCM not configured).
The air bag 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 RCM to complete the testing of the SRS. If the air bag 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 indicator will need to be repaired before diagnosis can continue.