Ford F150 Pickup. Instruction — part 1727

detects resistance that is out of the expected range (high or low), it will store Diagnostic Trouble Code (DTC)
B1877 or B1885 in memory and flash Code 46 on AIR BAG warning light.

Possible Causes

A left seat belt pretensioner out of range resistance fault can be caused by out of range resistance in Light
Green/Red wire, out of range resistance in Light Green/Black wire, out of range resistance in left seat belt
pretensioner or faulty RCM.

1. Check for hard or intermittent DTC

Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). See USING
SCAN TOOL under DIAGNOSTICS. Turn ignition switch to RUN position. Retrieve and record any
continuous DTCs. See RETRIEVING FAULT CODES under DIAGNOSTICS. Perform on-demand
self-test. See ON-DEMAND SELF-TEST under DIAGNOSTICS. If DTC B1877 or B1885 was
retrieved during on-demand self-test, fault is hard. Go to next step. If DTC B1877 or B1885 was not
retrieved, fault is intermittent. Go to step 4 .

2. Check left pretensioner circuit

Using scan tool, select PID/Data Monitor and Record. Select PID D-PRTNR. If resistance is less than 1.7
ohms or greater than 3.2 ohms, go to next step. If resistance is 1.7-3.2 ohms, replace RCM. See
RESTRAINTS CONTROL MODULE (RCM) under REMOVAL & INSTALLATION. Go to step 5 .

3. Check left pretensioner

Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM under
DISABLING & ACTIVATING AIR BAG SYSTEM. Turn ignition switch to RUN position. With PID
D-PRTNR selected on scan tool, read pretensioner resistance. If resistance is less than 1.7 ohms or greater
than 3.2 ohms, repair Light Green/Red wire (circuit No. 1079) and/or Light Green/Black wire (circuit No.
1080). See WIRING DIAGRAMS . Go to step 5 . If resistance is 1.7-3.2 ohms, replace left seat belt
pretensioner. See SEAT BELT PRETENSIONERS under REMOVAL & INSTALLATION.

4. Check for intermittent fault

Refer to continuous DTCs recorded in step 1 . If DTC retrieved in step 1 was an intermittent fault, check
for cause of intermittent faults in Light Green/Red wire (circuit No. 1079) and Light Green/Black wire
(circuit No. 1080). See WIRING DIAGRAMS . Attempt to recreate fault by flexing wire harness and
cycling ignition switch frequently. Repair any intermittent problems found. Go to next step. If DTC
retrieved in step 1 was not an intermittent fault. Go to next step.

5. Check for additional DTCs

Refer to continuous DTCs recorded in step 1 . If any continuous DTCs were retrieved, go to diagnostic
trouble code identification table for direction to appropriate test. See DIAGNOSTIC TROUBLE CODE
(DTC) IDENTIFICATION table. DO NOT clear any DTCs until all DTCs have been resolved. If no
continuous DTCs were retrieved, reconnect air bag system. Activate air bag system. See ACTIVATING

2003 Ford Pickup F150

2003 ACCESSORIES/SAFETY EQUIPMENT Air Bag Restraint Systems - F150 Pickup

SYSTEM under DISABLING & ACTIVATING AIR BAG SYSTEM. Clear all DTCs. See CLEARING
FAULT CODES under DIAGNOSTICS.

TEST F: LEFT PRETENSIONER CIRCUIT SHORT TO BATTERY OR IGNITION (DTC B1878)

Description

Restraints Control Module (RCM) monitors circuits to left seat belt pretensioner. When RCM detects a circuit
short to battery, it will store Diagnostic Trouble Code (DTC) B1878 in memory and flash Code 17 on AIR
BAG warning light.

Possible Causes

A left seat belt pretensioner circuit short to battery fault can be caused by short to battery in Light Green/Red
wire, short to battery in Light Green/Black wire, short to battery in left seat belt pretensioner or faulty RCM.

1. Check for hard or intermittent DTC

Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). See USING
SCAN TOOL under DIAGNOSTICS. Turn ignition switch to RUN position. Retrieve and record any
continuous DTCs. See RETRIEVING FAULT CODES under DIAGNOSTICS. Perform on-demand
self-test. See ON-DEMAND SELF-TEST under DIAGNOSTICS. If DTC B1878 was retrieved during
on-demand self-test, fault is hard. Go to next step. If DTC B1878 was not retrieved, fault is intermittent.
Go to step 4 .

2. Check left pretensioner

Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM under
DISABLING & ACTIVATING AIR BAG SYSTEM. Turn ignition switch to RUN position. Perform on-
demand self-test. If DTC B1878 was retrieved during on-demand self-test, go to next step. If DTC B1878
was not retrieved, replace left seat belt pretensioner. See SEAT BELT PRETENSIONERS under
REMOVAL & INSTALLATION. Go to step 5 .

3. Check left pretensioner circuits

Turn ignition switch to OFF position. Access RCM and disconnect harness connector. See
RESTRAINTS CONTROL MODULE (RCM) under REMOVAL & INSTALLATION. Remove left
pretensioner simulator from harness connector. Measure voltage between ground and harness side of
RCM connector terminals No. 18 (Light Green/Red wire, circuit No. 1079) and 22 (Light Green/Black
wire, circuit No. 1080) separately. See Fig. 14 . If voltage is more than 0.2 volt in either circuit, repair

NOTE:

Before proceeding, see AIR BAG SAFETY PRECAUTIONS .
Diagnostic tests or repairs are not to be performed on seat belt pretensioner
system with front seats installed in vehicle. Prior to diagnosis or repair of
pretensioner system, remove front seats and ensure appropriate pretensioner
simulators are installed at pretensioner connectors. See FRONT SEAT under
REMOVAL & INSTALLATION.

2003 Ford Pickup F150

2003 ACCESSORIES/SAFETY EQUIPMENT Air Bag Restraint Systems - F150 Pickup

short to battery in appropriate circuit. See WIRING DIAGRAMS . Go to step 5 . If voltage is less than
0.2 volt in both circuits, replace RCM. Go to step 5 .

4. Check for intermittent fault

Refer to continuous DTCs recorded in step 1 . If DTC retrieved in step 1 was an intermittent fault, check
for cause of intermittent faults in Light Green/Red wire (circuit No. 1079) and/or Light Green/Black wire
(circuit No. 1080). See WIRING DIAGRAMS . Attempt to recreate fault by flexing wire harness and
cycling ignition switch frequently. Repair any intermittent problems found. Go to next step. If DTC
retrieved in step 1 was not an intermittent fault. Go to next step.

5. Check for additional DTCs

Refer to continuous DTCs recorded in step 1 . If any continuous DTCs were retrieved, go to diagnostic
trouble code identification table for direction to appropriate test. See DIAGNOSTIC TROUBLE CODE
(DTC) IDENTIFICATION table. DO NOT clear any DTCs until all DTCs have been resolved. If no
continuous DTCs were retrieved, reconnect air bag system. Activate air bag system. See ACTIVATING
SYSTEM under DISABLING & ACTIVATING AIR BAG SYSTEM. Clear all DTCs. See CLEARING
FAULT CODES under DIAGNOSTICS.

TEST G: LEFT PRETENSIONER CIRCUIT SHORT TO GROUND (DTC B1879)

Description

Restraints Control Module (RCM) monitors circuits to left seat belt pretensioner. When RCM detects a circuit
short to ground, it will store Diagnostic Trouble Code (DTC) B1879 in memory and flash Code 17 on AIR
BAG warning light.

Possible Causes

A left seat belt pretensioner circuit short to ground fault can be caused by short to ground in Light Green/Red
wire, short to ground Light Green/Black wire, short to ground in left seat belt pretensioner or faulty RCM.

1. Check for hard or intermittent DTC

Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). See USING
SCAN TOOL under DIAGNOSTICS. Turn ignition switch to RUN position. Retrieve and record any
continuous DTCs. See RETRIEVING FAULT CODES under DIAGNOSTICS. Perform on-demand
self-test. See ON-DEMAND SELF-TEST under DIAGNOSTICS. If DTC B1879 was retrieved during
on-demand self-test, fault is hard. Go to next step. If DTC B1879 was not retrieved, fault is intermittent.

NOTE:

Before proceeding, see AIR BAG SAFETY PRECAUTIONS .
Diagnostic tests or repairs are not to be performed on seat belt pretensioner
system with front seats installed in vehicle. Prior to diagnosis or repair of
pretensioner system, remove front seats and ensure appropriate pretensioner
simulators are installed at pretensioner connectors. See FRONT SEAT under
REMOVAL & INSTALLATION.

2003 Ford Pickup F150

2003 ACCESSORIES/SAFETY EQUIPMENT Air Bag Restraint Systems - F150 Pickup

Go to step 4 .

2. Check left pretensioner

Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM under
DISABLING & ACTIVATING AIR BAG SYSTEM. Turn ignition switch to RUN position. Perform on-
demand self-test. If DTC B1879 was retrieved during on-demand self-test, go to next step. If DTC B1879
was not retrieved, replace left seat belt pretensioner. See SEAT BELT PRETENSIONERS under
REMOVAL & INSTALLATION. Go to step 5 .

3. Check left pretensioner circuits

Turn ignition switch to OFF position. Access RCM and disconnect harness connector. See
RESTRAINTS CONTROL MODULE (RCM) under REMOVAL & INSTALLATION. Remove left
pretensioner simulator from harness connector. Measure resistance between ground and harness side of
RCM connector terminals No. 18 (Light Green/Red wire, circuit No. 1079) and 22 (Light Green/Black
wire, circuit No. 1080) separately. See Fig. 14 . If resistance is less than 10 k/ohms in either circuit, repair
short to ground in appropriate circuit. See WIRING DIAGRAMS . Go to step 5 . If resistance is more
than 10 k/ohms in both circuits, replace RCM. Go to step 5 .

4. Check for intermittent fault

Refer to continuous DTCs recorded in step 1 . If DTC retrieved in step 1 was an intermittent fault, check
for cause of intermittent faults in Light Green/Red wire (circuit No. 1079) and/or Light Green/Black wire
(circuit No. 1080). See WIRING DIAGRAMS . Attempt to recreate fault by flexing wire harness and
cycling ignition switch frequently. Repair any intermittent problems found. Go to next step. If DTC
retrieved in step 1 was not an intermittent fault. Go to next step.

5. Check for additional DTCs

Refer to continuous DTCs recorded in step 1 . If any continuous DTCs were retrieved, go to diagnostic
trouble code identification table for direction to appropriate test. See DIAGNOSTIC TROUBLE CODE
(DTC) IDENTIFICATION table. DO NOT clear any DTCs until all DTCs have been resolved. If no
continuous DTCs were retrieved, reconnect air bag system. Activate air bag system. See ACTIVATING
SYSTEM under DISABLING & ACTIVATING AIR BAG SYSTEM. Clear all DTCs. See CLEARING
FAULT CODES under DIAGNOSTICS.

TEST H: RIGHT PRETENSIONER CIRCUIT RESISTANCE HIGH OR LOW (DTC B1881 OR 1886)

Description

NOTE:

Before proceeding, see AIR BAG SAFETY PRECAUTIONS .
Diagnostic tests or repairs are not to be performed on seat belt pretensioner
system with front seats installed in vehicle. Prior to diagnosis or repair of
pretensioner system, remove front seats and ensure appropriate pretensioner
simulators are installed at pretensioner connectors. See FRONT SEAT under
REMOVAL & INSTALLATION.

2003 Ford Pickup F150

2003 ACCESSORIES/SAFETY EQUIPMENT Air Bag Restraint Systems - F150 Pickup