Ford Mustang (1999-2004) Service Manual: Pinpoint Test J: LFC 34/DTC B1934 - Driver Air Bag Circuit Resistance Low

Normal Operation

The restraints control module (RCM) monitors the resistance of the driver air bag ignitor by measuring the resistance between pins 3 and 4. If the RCM detects low resistance between these pins, it will store a diagnostic trouble code (DTC) B1934 in memory and flash a lamp fault code (LFC) 34 (or higher priority code if one exists) on the air bag indicator.

Possible Causes

Driver air bag low resistance can be caused by:

  • a short in the clockspring windings.
  • a short in the wiring harness.
  • a low resistance in the driver air bag module.
  • an RCM internal concern.
  • worn or damaged short bar or camming beam.

PINPOINT TEST J: LFC 34/DTC B1934 - DRIVER AIR BAG CIRCUIT RESISTANCE LOW

Test Step Result / Action to Take
J1 CHECK FOR A HARD OR INTERMITTENT DTC Yes

This is a hard fault.

The fault condition is still present. This fault cannot be cleared until it is corrected and the DTC is no longer retrieved during the on-demand self test. GO to J2 .

No

This is an intermittent fault.

The fault condition is not present at this time. GO to J5 .

  • Key in OFF position.
  • Connect the diagnostic tool. Scan Tool
  • Key in ON position.
  • Enter the following diagnostic mode on the diagnostic tool: Retrieve/Clear Continuous DTCs.
  • Retrieve and record any continuous DTCs for use later in this pinpoint test.
  • Enter the following diagnostic mode on the diagnostic tool: On- Demand Self Test.
  • Was DTC B1934 retrieved during the on-demand self test?
J2 CHECK THE DRIVER AIR BAG MODULE Yes

GO to J3 .

No

INSTALL a new driver air bag module. GO to J6 .

WARNING: If the supplemental restraint system (SRS) is being serviced, the system must be deactivated and restraint system diagnostic tools must be installed. Refer to Air Bag Supplemental Restraint System (SRS) in this section.

The air bag restraint system diagnostic tools must be removed and the air bag modules reconnected when the system is reactivated to avoid non-deployment in a collision, resulting in possible personal injury.

NOTE: Diagnostics or repairs are not to be performed on a seat equipped with a seat side air bag with the seat in the vehicle. Prior to attempting to diagnose or repair a seat concern when equipped with a seat side air bag, the seat must be removed from the vehicle and the restraint system diagnostic tools must be installed in the seat side air bag electrical connectors. The restraint system diagnostic tools must be removed prior to operating the vehicle over the road.

NOTE: After diagnosing or repairing an SRS, the restraint system diagnostic tools must be removed before operating the vehicle over the road.

NOTE: After diagnosing or repairing a seat system, the restraint system diagnostic tools must be removed before operating the vehicle over the road.

NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer.

  • Key in OFF position.
  • Deactivate the system. Refer to Air Bag Supplemental Restraint System (SRS) in the Diagnosis and Testing portion of this section.
  • Key in OFF position.
  • Key in ON position.
  • Enter the following diagnostic mode on the diagnostic tool: On- Demand Self Test.
  • Was DTC B1934 retrieved?
J3 CHECK THE DRIVER AIR BAG MODULE CIRCUIT Yes

INSTALL a new RCM. GO to J6 .

No

GO to J4 .

  • Key in OFF position.
  • Disconnect: Driver Air Bag Restraint System Diagnostic Tool.
  • Measure the resistance between driver air bag C216, circuit 614 (GY/OG), harness side and between driver air bag C216, circuit 615 (GY/WH), harness side

  • Is the resistance greater than 10,000 ohms?
J4 CHECK THE CLOCKSPRING Yes

INSTALL a new clockspring. GO to J6 .

No

REPAIR the circuit (s) as necessary.

GO to J6 .

  • Disconnect: Clockspring C218b.
  • Measure the resistance between clockspring C218b, circuit 614 (GY/OG) and circuit 615 (GY/WH), harness side.

  • Is the resistance greater than 10,000 ohms?
J5 CHECK FOR AN INTERMITTENT FAULT Yes

CHECK for causes of intermittent low resistance on circuit 614 (GY/OG), circuit 615 (GY/WH), and the clockspring assembly. Attempt to recreate the hard fault by flexing the wire harness and cycling the ignition key frequently.

REPAIR any intermittent concerns found.

GO to J6 .

No

GO to J6 .

  • Refer to the continuous DTCs recorded during Step J1.
  • Was the continuous DTC retrieved during Step J1 an intermittent fault?
J6 CHECK FOR ADDITIONAL DTCs Yes

Do not clear any DTCs until all DTCs have been resolved. GO to the Restraints Control Module (RCM) Diagnostic Trouble Code (DTC) Priority Table in this section for pinpoint test direction.

No

RECONNECT the system.

REACTIVATE the system. PROVE OUT the system.

REFER to Air Bag Supplemental Restraint System (SRS) in this section. CLEAR all DTCs.

  • Refer to the continuous DTCs recorded during Step J1.
  • Were any continuous DTCs retrieved during Step J1?
    Pinpoint Test I: LFC 33/DTC B1933 - Passenger Air Bag Circuit Resistance High
    Normal Operation The restraints control module (RCM) monitors the resistance of the passenger air bag ignitor by measuring the resistance between pins 6 and 7. If the RCM detects high resistance ...

    Pinpoint Test K: LFC 35/DTC B1935 - Passenger Air Bag Circuit Resistance Low
    Normal Operation The restraints control module (RCM) monitors the resistance of the passenger air bag ignitor by measuring the resistance between pins 6 and 7. If the RCM detects low resistance ...

    Other materials:

    Handles, Locks, Latches And Mechanisms (Description and Operation)
    Lock Cylinders Individual lock cylinders are repaired by discarding the inoperative lock cylinder and building a new lock cylinder using the appropriate lock repair package. The lock repair package includes a detailed instruction sheet to build the ...

    Inspection and Verification
    Certain axle noise or vibration symptoms are also common to the engine, transmission, wheel bearings, tires, and other parts of the vehicle. For this reason, be sure that the cause of the trouble is in the axle before disassembling, adjusting or repairing th ...

    Dowels - Flywheel Housing to Block
    Removal 1. NOTE: Take care not to damage the flywheel housing to block dowel holes or the surface areas around the flywheel housing to block dowel hole during removal. Remove the two flywheel housing to block dowels using a drift pin where the flywheel ...