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Home >> Ford >> 2009 >> Mustang V6-4.0L >> Repair and Diagnosis >> Restraints and Safety Systems >> Air Bag Systems >> Testing and Inspection >> Initial Inspection and Diagnostic Overview >> Diagnostic Instructions

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. Run the Self Test to determine what on-demand and Continuous Memory Diagnostic Trouble Codes (CMDTCs) are being sensed by the RCM.

2. Retrieve all SRS DTCs and fault PIDs stored in the RCM 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.


Diagnostic Test Options

Scan tool options:

- Retrieve/Clear CMDTCs
- Self Test/On-Demand

Refer to the manufacturer's literature for the scan tool being used for correct scan tool test options.


Self Test/On-Demand

The Self Test option is used to verify that no electrical concerns exist with the SRS. Upon entering the self-test, the RCM 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 carried out after any repair to verify that the repair was successful.

To run the on-demand Self Test, 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 Self Test.

5. Select RCM.

6. The module will run the self-test and display on-demand (reflecting hard system concerns) and CMDTCs (historic) on the scan tool.

Self Test/Continuous Memory and Clear DTCs

During vehicle operation, the RCM 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 and module. DTCs can be retrieved with a scan tool using the Self Test option. All DTCs stored in the RCM 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 memory, as long as the concern no longer exists.

Once 128 ignition cycles have been recorded by the RCM since the concern was last detected, all CMDTCs will automatically be removed from memory.

To retrieve or clear DTCs, 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 Self Test.

5. Select RCM.

6. NOTE: Before proceeding with the clearing operation, make note of the DTCs displayed. Once cleared, DTCs cannot be retrieved.

All DTCs will be displayed on the screen.

7. Clear the DTCs. After clearing the DTCs, cycle the ignition OFF, then ON.
- CMDTCs that have been cleared will not reoccur as "continuous memory" in the same ignition cycle. Only new DTCs which were
not present before clearing can occur as "continuous memory" after clearing.


DataLogger PID/Data

The DataLogger PID/Data option allows the scan tool operator to read the state of PIDs to aid in diagnosing the system. PIDs are real-time measurements of parameters, such as voltages and resistances, that are calculated by the RCM and 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.


Active Commands

This command allows the technician to verify operation of the air bag warning indicator, the PAD indicator and chime. When the air bag output command is executed, the indicator(s) and the chime are activated simultaneously for approximately 4 seconds. All 3 of the devices are deactivated automatically.


Lamp Fault Code (LFC)

When the RCM detects a system fault, it will cause the air bag warning indicator to flash a coded sequence; a LFC. 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 a LFC.

Each LFC is flashed 5 times after which the air bag indictor will remain lit for the remainder of the ignition cycle. If there are multiple LFCs, each LFC will flash in order of priority.

Each LFC has one or more associated DTCs.


Diagnosing Customer Concerns With On-Demand DTCs

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 Diagnostic Trouble Codes (CMDTCs)

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.


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 bit-mapped 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 CMDTCs (historic). 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 (CMDTCs). Refer to the manufacturer's instructions for the scan tool being used on how to view fault PIDs.


Prove Out Procedure

Turn the ignition from the OFF to the ON position and visually monitor the air bag warning indicator with all SRS components connected or restraint system diagnostic tools installed. The air bag warning indicator will light 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 flashing might not occur until approximately 30 seconds after the ignition 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 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.
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