Ford Fiesta (2011 year). Manual — part 81

Diagnosing Customer Concerns
Without Hard DTCs

WARNING: To avoid accidental
deployment, the restraints control module
(RCM) backup power supply must be
depleted. Wait at least one minute after
disconnecting the battery ground cable(s)
before commencing any repair or
adjustment to the supplemental restraint
system (SRS), or any component(s)
adjacent to the SRS sensors. Failure to
follow these instructions may result in
personal injury.

NOTE: Following the pinpoint tests when a
diagnostic trouble code (DTC) is not present, or
the air bag warning lamp is not permanently
illuminated, will result in needless replacement of
air bag system components and repeat repairs.

Speak with the customer to determine if a particular
set of conditions must be met in order for a fault to
occur. If an illuminated air bag warning lamp is
reported by the customer but is not present when
the vehicle comes in for repair, pinpoint test
diagnostics cannot be used.

Diagnosing Customer Concerns with
Hard DTCs

WARNING: Do not use substitute air bag
simulators when working on the SRS. Use
only the appropriate tool. Failure to follow
these instructions may result in personal
injury.

Most air bag system diagnostic procedures require
the use of system deactivation and system
reactivation procedures. These procedures require
the air bag module(s) and safety belt retractor
pretensioners to be disconnected from the SRS,
thereby removing the risk of air bag deployment
while diagnostics are carried out.

Air bag simulators are required to carry out
diagnosis and testing of the air bag system. The
simulator contains a resistor, used to simulate an
air bag module connection to the system. It is not
acceptable to short-circuit the air bag module
connections with a 0 ohm jumper wire. If a 0 ohm
jumper wire is used to short-circuit the air bag
module connections, an illuminated air bag warning
lamp will be displayed and a DTC logged by the
RCM.

Deactivation

WARNING: To avoid accidental
deployment, the RCM backup power supply
must be depleted. Wait at least one minute
after disconnecting the battery ground
cable(s) before commencing any repair or
adjustment to the SRS, or any
component(s) adjacent to the SRS sensors.
Failure to follow these instructions may
result in personal injury.

1. Disconnect the battery ground cable.

REFER to: Battery Disconnect and Connect

(414-01 Battery, Mounting and Cables,
General Procedures).

• Wait at least one minute for the backup power

supply in the RCM to deplete its stored energy.

WARNING: To minimize the possibility of
premature deployment, live air bag
modules must only be placed on work
benches which have been ground bonded
and with the trim cover facing up. Failure
to follow these instructions may result in
personal injury.

• Remove the driver air bag module from the

vehicle.

REFER to: Driver Air Bag Module

(501-20

Supplemental Restraint System, Removal and
Installation).

• NOTE: REFER to FordEcat for a compatible

driver air bag module wiring harness to use as
a test lead.

Connect a test driver air bag module wiring
harness to the clockspring.

• Connect the simulator (501-073A) to the driver

air bag module wiring harness in place of the
driver air bag module at the top of the steering
column.

• Remove the driver lower air bag module from

the vehicle.

• Connect the simulator (501-073A) to the wiring

harness in place of the driver lower air bag
module.

• Disconnect the passenger air bag module

electrical connector.

REFER to: Passenger Air Bag Module

(501-20

Supplemental Restraint System, Removal and
Installation).

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• Connect the simulator (501-073A) to the wiring

harness in place of the passenger air bag
module.

• Disconnect the side air curtain module electrical

connectors on both sides.

REFER to: Side Air Curtain Module

(501-20

Supplemental Restraint System, Removal and
Installation).

• Connect the simulators (501-073A) to the wiring

harnesses in place of the side air curtain
modules.

• Disconnect the side air bag module electrical

connectors on both sides.

REFER to: Side Air Bag Module

(501-20

Supplemental Restraint System, Removal and
Installation).

• Connect the simulators (501-401) to the wiring

harnesses in place of the side air bag modules.

• Detach the driver side B-pillar trim panel to gain

access to driver side safety belt retractor
pretensioner electrical connector. REFER to:

B-Pillar Trim Panel - 5-Door

(501-05 Interior

Trim and Ornamentation, Removal and
Installation).

• Disconnect the driver side safety belt retractor

pretensioner electrical connector.

• Connect the simulator (501-073A) to the wiring

harness in place of the driver side safety belt
retractor pretensioner.

• Detach the passenger side B-pillar trim panel

to gain access to passenger side safety belt
retractor pretensioner electrical connector.
REFER to:

B-Pillar Trim Panel - 5-Door

(501-05 Interior

Trim and Ornamentation, Removal and
Installation).

• Disconnect the passenger side safety belt

retractor pretensioner electrical connector.

• Connect the simulator (501-073A) to the wiring

harness in place of the passenger side safety
belt retractor pretensioner.

• Connect the battery ground cable.

REFER to: Battery Disconnect and Connect

(414-01 Battery, Mounting and Cables,
General Procedures).

Reactivation

WARNING: The air bag simulators must be
removed and the air bag modules
reconnected when reactivated to avoid
non-deployment in a collision. Failure to
follow this instruction may result in
personal injury.

1. Disconnect the battery ground cable.

REFER to: Battery Disconnect and Connect

(414-01 Battery, Mounting and Cables,
General Procedures).

• Wait at least one minute for the backup power

supply in the RCM to deplete its stored energy.

• NOTE: If a new driver air bag module wiring

harness has been used for testing, the wiring
harness should be retained for future test use
only.

Remove the simulator (501-073A) from the
driver air bag module wiring harness at the top
of the steering column.

• Remove the driver air bag module wiring

harness from the clockspring.

• Connect and install the driver air bag module.

REFER to: Driver Air Bag Module

(501-20

Supplemental Restraint System, Removal and
Installation).

• Remove the simulator (501-073A) from the

sub-harness at the driver lower air bag module.

• Connect and install the driver lower air bag

module.

• Remove the simulator (501-073A) from the

passenger air bag module wiring harness.

• Connect and install the passenger air bag

module.

REFER to: Passenger Air Bag Module

(501-20

Supplemental Restraint System, Removal and
Installation).

• Remove the simulators (501-073A) from the

side air curtain module wiring harnesses.

• Connect and install the side air curtain modules.

REFER to: Side Air Curtain Module

(501-20

Supplemental Restraint System, Removal and
Installation).

• Remove the simulators (501-41) from the side

air bag module wiring harnesses.

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• Connect and install the side air bag modules.

REFER to: Side Air Bag Module

(501-20

Supplemental Restraint System, Removal and
Installation).

• Remove the simulator (501-073A) from the

driver side safety belt retractor pretensioner
wiring harness.

• Connect the driver side safety belt retractor

pretensioner electrical connector.

• Attach the driver side B-pillar trim panel. REFER

to:

B-Pillar Trim Panel - 5-Door

(501-05 Interior

Trim and Ornamentation, Removal and
Installation).

• Remove the simulator (501-073A) from the

passenger side safety belt retractor
pretensioner.

• Connect the passenger side safety belt retractor

pretensioner electrical connector.

• Attach the passenger side B-pillar trim panel.

REFER to:

B-Pillar T

rim

Panel - 5-Door

(501-05 Interior

Trim and Ornamentation, Removal and
Installation).

• Connect the battery ground cable.

REFER to: Battery Disconnect and Connect

(414-01 Battery, Mounting and Cables,
General Procedures).

• Prove out the system.

Glossary

Air Bag Simulator

Air bag simulators are used to simulate air bag
module connections to the system.

Deactivate the System

Deactivate the system means to carry out the
deactivation procedure. REFER to Deactivation in
this procedure.

Prove Out the System

The air bag warning indicator will illuminate for
three seconds. If there is a fault condition, the air
bag warning indicator will stay illuminated or
illuminate after a five second delay.

Reactivate the System

Reactivate the system means to carry out the
reactivation procedure. REFER to Reactivation in
this procedure.

Principles of Operation

SRS Operation

The vehicle is equipped with a DC fired sensing
system.

In the event of a severe frontal or three-quarter
frontal impact, in excess of a predetermined limit,
the driver and passenger front air bags and safety
belt retractor pretensioners and driver knee air bag
(if equipped) will deploy.

In the event of a severe full side impact, in excess
of a predetermined limit, either the driver or
passenger side air bag, side air curtain (if
equipped) will deploy.

Air bag deployment will only occur, in the event of
a severe collision, when the ignition key is in the
RUN position. The passenger air bag deactivation
(PAD) switch (if equipped) will deactivate the
passenger frontal air bag in the event of a severe
frontal impact; it will not deactivate any other
deployable device.

RCM

The RCM retains full control of the whole system,
providing continual system checks and full
diagnostic capabilities. The non-volatile memory
stores the diagnostic trouble codes, which can then
be downloaded through the data link connector
(DLC) to the Ford diagnostic equipment.

In the event of a failure in the vehicle supply during
an accident, the RCM provides a backup power
supply, sufficient to deploy the air bag(s) for a
minimum of 150 ms. The backup power supply is
discharged by the RCM within 60 seconds of the
battery ground cable being disconnected.

The RCM contains electronic acceleration sensors
which measure the longitudinal acceleration and
the lateral acceleration and provide both signals
to the micro-controller proportional to the amount
of acceleration measured. The RCM also contains
a safing sensor, which prevents unintentional
deployment of the front air bags and safety belt
retractor pretensioners and knee air bag (if
equipped) in the event of a fault within the

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electronic acceleration sensor(s). The RCM
compares the values it receives from the crash
sensor, side impact sensors, safing sensor and the
internal electronic sensors. If the deceleration due
to a frontal or side impact exceeds a stored
threshold value then the RCM triggers the air bags
and safety belt pretensioners as required.

Front Crash Sensor

The front crash sensor contains an acceleration
sensor, filter, amplifier and an application specific
integrated circuit for signal transmitting and is
mounted on the radiator grille opening panel
reinforcement. The crash sensor sends a signal at
a level determined by the crash severity to the
RCM. The RCM will evaluate the signal against
stored data and deploy the frontal air bags and
safety belt retractor pretensioners and knee air bag
(if equipped) when required. Both the crash sensor
and the internal RCM longitudinal acceleration
sensor must exceed a preset limit to initiate the air
bag.

Side Impact Sensor

The side impact sensors are mounted at the base
of the B-pillar on either side of the vehicle, to
facilitate remote lateral impact sensing. Each side
impact sensor contains an acceleration sensor,
filter, amplifier and an application specific
integrated circuit for signal transmitting. In the event
of an impact, in excess of a predetermined limit,
the side impact sensor sends a signal at a level
determined by the crash severity to the RCM. The
RCM will evaluate the signal against stored data
and deploy the side air bag on the side the
deployment request was initiated. Both the side
impact sensor and the internal RCM lateral
acceleration sensor must exceed a preset limit to
initiate the air bag. The RCM retains control of the
side air bags, side air curtains.

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Supplemental Restraint System

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