Ford 2003 Mustang Workshop Manual page 4032

Pinpoint Test B: LFC 21/DTC B1921 — RCM Bracket Ground Resistance High
Normal Operation
WARNING: The tightening torque of the restraints control module (RCM) retaining bolts is
critical for proper air bag supplemental restraint system (SRS) operation. Refer to
Control Module (RCM)
The restraints control module (RCM) monitors the resistance between the ground connections at its
housing and the reference ground at pin 21. If the RCM detects a resistance greater than 100 ohms, it
will store a diagnostic trouble code (DTC) B1921 in memory and flash a lamp fault code (LFC) 21 (or
higher priority code if one exists) on the air bag indicator.
Possible Causes
High resistance between the RCM housing ground and pin ground can be caused by:
incorrect seating of the RCM retaining bolts.
incorrect tightening torque of the RCM retaining bolts.
high resistance on RCM logic ground circuit 397 (BK/WH).
PINPOINT TEST B: LFC 21/DTC B1921 — RCM BRACKET GROUND
RESISTANCE HIGH
B1 CHECK FOR A HARD OR INTERMITTENT DTC
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 B1921 retrieved during the on-demand self
in this section for correct torque values.
Test Step
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.
Restraints
Result / Action to Take
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
B2 .
No