Pinpoint Test H: LFC 14/DTC B1921 - Air Bag Diagnostic Monitor Circuit Open

WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: When installing a new restraints control module (RCM), always make sure the correct RCM is being installed. The RCM 40-pin connector is keyed differently for vehicles with safety canopies and side air bags than the 40-pin connector for vehicles without safety canopies and side air bags. Do not force the 40-pin connector onto the RCM. If the connector is forced onto the RCM, damage to the RCM and/or connector will occur.

NOTE: Most faults are due to connector and/or wiring concerns. Carry out a thorough Inspection and Verification before proceeding with the Pinpoint Test.

H1 CHECK FOR CONTINUOUS OR ON-DEMAND DTCs
WARNING:
1. Restraint system diagnostic tools are for service only. Tools must be removed prior to operating the vehicle over the road. Failure to remove restraint system diagnostic tools could result in injury and possible violation of vehicle safety standards.
2. Do not handle, move or change the original horizontal mounting position of the restraints control module (RCM) while the RCM is connected and the ignition switch is ON. Failure to follow these instructions may result in the inadvertent deployment of the safety canopy and risk of personal injury.
3. Never probe the connectors on the air bag module. Doing so can result in air bag deployment, which can result in personal injury.
4. The safety belt pretensioner is a pyrotechnic device. Always wear safety glasses when repairing an air bag equipped vehicle and when handling a safety belt buckle pretensioner or safety belt retractor pretensioner. Never probe a pretensioner electrical connector. Doing so could result in pretensioner or air bag deployment and could result in personal injury.
5. Never probe the electrical connector on a safety canopy module. Doing so can result in safety canopy deployment.
NOTE:
1. If a seat equipped with a supplemental restraint system (SRS) component is being serviced, the SRS must be depowered.
2. After diagnosing or repairing an SRS, the restraint system diagnostic tools must be removed before operating the vehicle over the road .
3. The SRS must be fully operational and free of faults before releasing the vehicle to the customer.
- Enter the following diagnostic mode on the scan tool: On-Demand Self Test.
- Enter the following diagnostic mode on the scan tool: Retrieve/Record Continuous DTCs.
- Was DTC B1921 retrieved during the on-demand self test?
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 H2.

No: This is an intermittent fault. The fault condition is not present at this time. GO to H5.
H2 INSPECT THE RCM MOUNTING, MOUNTING BRACKET AND MOUNTING SURFACE
- Key in OFF position.
- Depower the system. Refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING .
- Inspect the RCM mounting and make sure that the retaining bolts are fully seated and tightened correctly.
- Remove the RCM. Refer to RESTRAINTS CONTROL MODULE (RCM) .
- Visually inspect the RCM, mounting bracket and mounting surface for damage, corrosion or dirt.
- Was a significant amount of corrosion or dirt found, the RCM mounting bracket attached to the mounting surface incorrectly or were the RCM bolts not fully seated and tightened correctly?
Yes: CLEAN, TIGHTEN bolts or REPAIR the mounting surface as necessary. REINSTALL the RCM and mounting bracket to the mounting surface. GO to H6.

No: GO to H3.
H3 INSTALL THE RCM AND CARRY OUT THE ON-DEMAND SELF TEST
- Clean the RCM mounting surfaces and bolts.
- Install the RCM. Refer to RESTRAINTS CONTROL MODULE (RCM) .
- Repower the system. Do not prove out the system at this time. Refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING .
- Enter the following diagnostic mode on the scan tool: On-Demand Self Test.
- Was DTC B1921 retrieved during the on-demand self test?
Yes: GO to H4.

No: Fault corrected. GO to H6.
H4 CHECK GROUND CIRCUIT 1203 (BK/LB) FOR HIGH RESISTANCE
- Key in OFF position.
- Depower the system. Refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING .
- Disconnect: RCM C2041a and C2041b.
- Measure the resistance between RCM C2041a-16, circuit 1203 (BK/LB), harness side and the RCM case ground.
  
  Fig 1: Checking Ground Circuit 1203 (BK/LB) For High Resistance
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes: INSTALL a new RCM. REFER to RESTRAINTS CONTROL MODULE (RCM) . GO to H6.

No: REPAIR circuit 1203 (BK/LB). GO to H6.
H5 CHECK FOR AN INTERMITTENT FAULT
- Key in OFF position.
- Enter the following diagnostic mode on the scan tool: On-Demand Self Test.
- Was DTC B1921 retrieved during the on-demand self test?
Yes: This is a hard fault. The fault condition is now 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 H2.

No: CHECK for causes of intermittent high resistance on circuit 1203 (BK/LB) or the chassis ground. ATTEMPT to recreate the hard fault by flexing the wire harness and cycling the ignition key frequently. REPAIR any intermittent concerns found. GO to H6.
H6 CHECK FOR ADDITIONAL DTCs
- Refer to the continuous DTCs recorded during Step H1.
- Were any continuous DTCs retrieved during Step H1 ?
Yes: Do not clear any DTCs until all DTCs have been resolved. GO to the RESTRAINTS CONTROL MODULE (RCM) DIAGNOSTIC TROUBLE CODE (DTC) TABLE for pinpoint test direction.

No: RECONNECT the system. If previously directed to deactivate the system, REACTIVATE the system. REFER to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEACTIVATION AND REACTIVATION . REPOWER the system. REFER to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING . PROVE OUT the system. CLEAR all DTCs.