[52B] SUPPLEMENTAL RESTRAINT SYSTEM (SRS) - - TROUBLESHOOTING - DIAGNOSTIC TROUBLE CODE PROCEDURES - Diagnosis code 24: Passenger’s (Front) Air Bag Module (Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit)PRINT PAGE / INDEX / PRIOR / NEXT
Diagnosis code 24: Passenger’s (Front) Air Bag Module (Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit)
OPERATION
  • The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the front air bag analog G-sensor. If the impact is over a predetermined level, the SRS-ECU outputs an ignition signal. At this time, if the front air bag safing G-sensor is on, the SRS air bag will inflate.
  • The ignition signal is input to the air bag module via the clock spring to inflate the air bag.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if there is abnormal resistance between the input terminals of the passenger's side air bag module (squib). However, if no diagnosis code resets, the SRS warning lamp will be switched off (diagnosis code will be retained).
PROBABLE CAUSES
  • Improper engaged connector or defective short spring*
  • Short circuit between the passenger's air bag module (squib) circuit terminals
  • Damaged connector(s)
  • Malfunction of the SRS-ECU
NOTE: *: The squib circuit connectors integrate a "short" spring (which prevents the air bag from deploying unintentionally due to static electricity by shorting the positive wire to the earth wire in the squib circuit when the connectors are disconnected).Therefore, if connector C-115 or C-09 is damaged or improperly engaged, the short spring may not be released when the connector is connected.
DIAGNOSIS PROCEDURE
STEP 1. MUT-II/III diagnosis code
 CAUTION
 To prevent damage to MUT-II/III, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting MUT-II/III.
  1. Turn the ignition switch to the "ON" position.
  1. Check if the diagnosis code is set.
  1. Turn the ignition switch to the "LOOK" (OFF) position.
Q: Is diagnosis code 34 set?
YES:  Go to Step 2.
NO:  Go to Step 3.
STEP 2. Connector check: SRS-ECU connector C-115
Q: Is the connector correctly engaged?
YES:  Go to Step 3.
NO:  Engage the connector correctly. Then go to Step 7.
STEP 3. Connector check: SRS-ECU connector C-115 and passenger’s air bag module connector C-09 (Check whether the diagnosis code is reset).
  1. Disconnect the negative battery terminal.
  1. Disconnect connectors C-115 and C-09, and then reconnect them.
  1. Connect the negative battery terminal.
  1. Erase the diagnosis code memory, and check the diagnosis code.
Q: Is diagnosis code 24 set?
YES:  Go to Step 4.
NO:  The procedure is complete. It is assumed that diagnosis code 24 set as connector C-115 or C-09 was engaged improperly.
STEP 4. Check the passenger's air bag module (Check whether the diagnosis code is reset).
  1. Disconnect the negative battery terminal.
  1. Unclip passenger’s air bag module connector C-09.
       
    1. Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
       CAUTION
       Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
    1. Disconnect the passenger's air bag module connector C-09 and insert special tool MB991866 into the harness side connector by backprobing.
    1. Connect the negative battery terminal.
    1. Erase the diagnosis code memory, and check the diagnosis code.
    Q:  Is diagnosis code 24 set?
    YES:  Go to Step 5.
    NO:  Replace the passenger's air bag module (Refer to ). Then go to Step 7.
    STEP 5. Check the passenger’s air bag module circuit at SRS-ECU connector C-115.
    1. Disconnect SRS-ECU connector C-115.
    1. Unclip passenger’s air bag module connector C-09.
       DANGER
       To prevents the air bag from deploying unintentionally, disconnect the passenger’s air bag module connector C-09 to short the squib circuit.
    1. Disconnect the passenger's air bag module connector C-09.
       
       CAUTION
       Insert an insulator such as a cable tie to a depth of 4 mm or more, otherwise the short spring will not be released.
    1. Insert a cable tie [3 mm wide, 0.5 mm thick] between terminals 9, 10 and the short spring to release the short spring.
       
       CAUTION
       Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
    1. Check for continuity between C-115 harness side connector terminals 9 and 10.
      2. OK: Open circuit
    Q: Is the check result normal?
    YES:  Erase the diagnosis code memory, and check the diagnosis code. If diagnosis code 24 sets, replace the SRS-ECU (Refer to ). Then go to Step 7 .
    NO:  Go to Step 6.
    STEP 6. Check the harness for short circuit between SRS-ECU connector C-115 (terminal No.9 and 10) and passenger’s air bag module connector C-09 (terminal No.1 and 2).
    Q: Are harness wires between SRS-ECU connector C-115 (terminal No.9 and 10) and passenger’s air bag module connector C-09 (terminal No.1 and 2) in good condition?
    YES:  Go to Step 7    .
    NO:  Repair the harness wires between SRS-ECU connector C-115 and passenger’s air bag module connector C-09. Then go to Step 7.
    STEP 7. Check whether the diagnosis code is reset.
    Q: Is diagnosis code 24 set?
    YES:  Return to Step 1    .
    NO:  The procedure is complete. (If no malfunctions are found in all steps, an intermittent malfunction is suspected). Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points .
    [52B] SUPPLEMENTAL RESTRAINT SYSTEM (SRS) - - TROUBLESHOOTING - DIAGNOSTIC TROUBLE CODE PROCEDURES - Diagnosis code 24: Passenger’s (Front) Air Bag Module (Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit)PRINT PAGE / INDEX / PRIOR / NEXT
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