Airbag System Description

AIRBAG SYSTEM
The Airbag Control Module (ACM) is secured to a bracket on the floor panel transmission tunnel below the instrument panel inside the vehicle. The ACM mounting bracket also serves as the instrument; panel center support. The ACM contains a microprocessor, the impact sensor, and energy storage capacitor. The microprocessor contains the air-bag system logic. The ACM system logic includes On-Board Diagnostics (OBD) capability, and communicates with the instrument cluster circuitry on the Chrysler Collision Detection (CCD) data bus to control the airbag indicator lamp.

The microprocessor in the ACM monitors the impact sensor signal and the airbag system electrical circuits to determine the system readiness. If the ACM detects a monitored system fault, it sends messages to the instrument cluster on the CCD data bus to turn ON the airbag indicator lamp. A pre-programmed decision algorithm in the ACM microprocessor determines when the deceleration rate signaled by the impact sensor indicates an impact that is severe enough to require airbag system protection. when the programmed conditions are met, the ACM sends and electrical signal to deploy the airbag system components.

Only one impact sensor is used in this airbag system. The impact sensor is an accelerometer that senses the rate of the vehicle deceleration, which provides verification of the direction and severity of an impact. The impact sensor is calibrated for the specific vehicle, and is only serviced as a unit with the ACM.

The ACM also contains an energy-storage capacitor. This capacitor stores enough electrical energy to deploy the airbags, for one second following a battery disconnect or failure during and impact. The purpose of the capacitor is to provide airbag system protection in a severe secondary impact if the initial impact has damaged or disconnected the battery, but was not severe enough to deploy the airbags.

THE AIRBAG SYSTEM IS A SENSITIVE,COMPLEX ELECTROMECHANICAL UNIT.BEFORE ATTEMPTING TO DIAGNOSE OR SERVICE ANY AIRBAG SYSTEM OR RELATED STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENTS YOU MUST FIRST DISCONNECT AND ISOLATE THE BATTERY NEGATIVE ROUND CABLE. THEN WAIT TWO MINUTES FOR THE SYSTEM CAPACITOR TO CHARGE BEFORE FURTHER SYSTEM SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO DO THIS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY. NEVER STRIKE OR KICK THE AIRBAG CONTROL MODULE, AS IT CAN DAMAGE THE IMPACT SENSOR OR AFFECT ITS CALIBRATION. IF AN AIRBAG CONTROL MODULE IS ACCIDENTALLY DROPPED DURING SERVICE, THE MODULE MUST BE SCRAPPED AND REPLACED WITH A NEW UNIT.

The AIRBAG warning lamp is the only point at which the customer can observe "symptoms" of a system malfunction. Whenever the ignition key is turned to the "run" or "start" position, the MIC performs a lamp check by turning the AIRBAG warning lamp ON for 6-8 seconds. If the lamp remains OFF; it means that the ACM has checked the system and found it to be free of discernible malfunctions. If the lamp remains ON, there could be an active fault in the system or the MIC lamp circuit may be internally shorted to ground, If the lamp comes ON and stays ON for a period longer than 6-8 seconds then goes OFF; there is usually an intermittent problem in the system.

The MIC monitors the airbag warning lamp and seat belt warning lamp during the bulb check for a defective bulb or lamp driver circuit. The MIC tests the airbag lamp during the cluster bulb check and substitutes the seat belt lamp if the airbag lamp is defective. If the airbag lamp is defective the MIC will turn the seat belt light ON and OFF approximately 30 times to warn the driver that the airbag lamp is defective. The lamp status is sent to the ACM continuously via a CCD bus message. The seat belt lamp acts as a backup in the event that the AIRBAG lamp is defective. This information is sent to the ACM continuously via a CCD bus message.

Perform the WARNING LAMP BULB OR DRIVER procedure in this book to find the cause of any customer complaint regarding the AIRBAG warning lamp, such as:
- warning lamp does not illuminate
- warning lamp stays illuminated with no active DTC's

Club cab and quad cab models of this vehicle are equipped with a structural seat belt system. The structural seat belt system includes a Seatbelt Control Timer Module (SCTM). The SCTM has a hardwired input to the ACM. If a fault input form the SCTM is detected, or the SCTM is not connected, the ACM sends a message to the instrument cluster on the CCD data bus to turn ON the seat belt reminder lamp. See Seat Belt Control Timer Module.

ACM cannot be repaired or adjusted and, if damaged or faulty, it must be replaced.

DRIVER AIRBAG MODULE (DAB)
The airbag protective trim cover is the most visible part of the driver side airbag system. The module is mounted directly to the steering wheel. Located under the trim cover are the horn switch, the airbag cushion, and the airbag cushion supporting components. The airbag module includes a housing to which the cushion and inflator are attached and sealed. The airbag module cannot be repaired, and must be replaced if deployed or in any way damaged. The inflator assembly is mounted to the back of the airbag module. The inflator seals the hole in the airbag cushion so it can discharge the gas it produces directly into the cushion when supplied with the proper electrical signal. The protective trim cover is fitted to the front of the airbag module and forms a decorative cover in the center of the steering wheel. Upon airbag deployment, this cover will split at a predetermined breakout line.

THE AIRBAG MODULE INFLATOR ASSEMBLY CONTAINS SODIUM AND POTASSIUM NITRATE. THESE MATERIALS ARE POISONOUS AND EXTREMELY FLAMMABLE. CONTACT WITH ACID, WATER, OR HEAVY METALS MAY PRODUCE HARMFUL AND IRRITATING GASES (SODIUM HYDROXIDE IS FORMED IN THE PRESENCE OF MOISTURE) OR COMBUSTIBLE COMPOUNDS. IN ADDITION, THE PASSENGER AIRBAG MODULE CONTAINS ARGON GAS PRESSURIZED OVER 2500 PSI. DO NOT ATTEMPT TO DISMANTLE AN AIRBAG MODULE OR TAMPER WITH ITS INFLATOR. DO NOT PUNCTURE, INCINERATE, OR BRING INTO CONTACT WITH ELECTRICITY. DO NOT STORE AT TEMPERATURE EXCEEDING 93°C (200°F).

PASSENGER AIRBAG MODULE (PAB)
The airbag door in the instrument panel top cover above the glove box is the most visible part of the passenger side airbag system. Located under the airbag door is the airbag cushion and it's supporting components. The airbag module includes a housing to which the cushion and inflator are attached and sealed. The airbag module includes a housing to which the cushion and inflator are attached and sealed. The airbag module cannot be repaired, and must be replaced if deployed or in any way damaged. The inflator assembly is mounted to the back of the airbag module. The inflator includes a small canister of highly compressed argon gas. The inflator seals the hole in the airbag cushion so it can discharge the compressed gas it contains directly into the cushion when supplied with the proper electrical signal. The airbag door has a living hinge at the top, which is secured to the instrument panel top cover. The door also has predetermined breakout lines concealed beneath its decorative cover. Upon airbag deployment, the airbag door will split at the breakout lines and the door will pivot out of the way.

The airbag module is secured at the bottom to the steel structural base of the instrument panel above the glove box opening. The airbag door is serviced as a unit with the passenger side airbag module, and includes the two passenger heating and air conditioning panel outlet housings. Following an airbag deployment, the airbag module and the instrument panel assembly must be replaced.

AIRBAG DIAGNOSTIC TROUBLE CODES
Airbag diagnostic trouble codes consist of active and stored codes. If more than one code exists, diagnostic priority should be give to the active codes.

Active diagnostic trouble codes for the airbag system are not permanent and will change the moment the reasoning for the code is corrected. In certain test procedures, diagnostic trouble codes are used as a diagnostic tool.

Active Codes
The code becomes active as soon as the malfunction is detected or key-OFF, whichever occurs first. An active trouble code indicates an on-going malfunction. This means that the defect is currently there every time the airbag control module checks that circuit/function. It is impossible to erase an active code; active codes automatically erase by themselves when the reason for the code has been corrected.

With the exception of the warning lamp trouble codes or malfunctions, when a malfunction is detected, the airbag lamp remains lit for a maximum of 12 seconds or as long as the malfunction is present.

The seat belt lamp replaces the airbag lamp if the airbag lamp is defective. The seat belt lamp pulses ON and OFF 30 times if the airbag warning lamp is defective.

Stored Codes
Airbag codes are automatically stored in the ACM's memory as soon as the malfunction is detected. The exception is the "Loss of Ignition Run Only" code which is an active code only.

A "stored" code indicates there was an active code present at some time. However, the code currently may not be present as an active code, although another active code could be.

When a trouble code occurs, the airbag warning lamp illuminates for 2 seconds minimum (even if the problem existed for less than 2 seconds). The code is stored, along with the time in minutes it was active, and the number of times the ignition has been cycled since the problem was last detected.

The minimum time shown for any code will be one minute, even if the code was actually present for less than one minute. Thus, the time shown for a code that was present for two minutes 2 seconds, for example, would be three minutes.

If a malfunction is detected a diagnostic trouble code is stored and will remain stored as long as the malfunction exists. When and if the malfunction ceases to exist, an ignition cycle count will be initiated for that code. If the ignition cycle count reaches 100 without a reoccurrence of the same malfunction, the diagnostic trouble code is erased and that ignition cycle counter is reset to zero. If the malfunction reoccurs before the count reaches 100, then the ignition cycle counter will be reset and the diagnostic trouble code will continue to be a stored code.

If a malfunction is not active while performing a diagnostic test procedure, the active code diagnostic test will not locate the source of the problem. In this case, the stored code can indicate an area to inspect.

If no obvious problems are found, erase stored codes, and with the ignition "ON" wiggle the wire harness and connectors, rotate the steering wheel from stop to stop. Recheck for codes periodically as you work through the system. This procedure may uncover a malfunction that is difficult to locate.

Airbag Trouble Codes
The airbag control module may report any of the following diagnostic trouble codes.

For these codes, replace the Airbag Control Module (ACM) even if set intermittently:
- ACM ACCELEROMETER......FIRING CAPACITOR LOW
- AECM OUTPUT DRIVER CIRCUIT OPEN......LOGIC CAPACITOR LOW
- AECM INTERNAL DIAGNOSTIC CODE # 1......SAFING SENSOR SHORTED
- WARNING LAMP DRIVER ERROR

For these codes, refer to the appropriate diagnostic procedure:
- Cluster Message Mismatch
- Driver Squib Circuit Open
- Driver Squib Circuit Shorted
- Driver Squib Circuit Shorted to Battery
- Driver Squib Circuit Shorted to Ground
- Loss of Ignition Run Only
- Loss of Ignition Run/Start
- No Cluster CCD Message
- Missing or Invalid VIN
- Passenger Squib Circuit Open
- Passenger Squib Circuit Shorted
- Passenger Squib Circuit Shorted to Battery
- Passenger Squib Circuit Shorted to Ground
- SCTM Failure
- SCTM Message Mismatch
- VIN Mismatch
- Warning Lamp Bulb or Driver