B1B79
B1B79 - PASSENGER SEAT WEIGHT SENSOR 3 - LEFT FRONT INPUT CIRCUIT LOWB1B79 - Passenger Seat Weight Sensor 3 - Left Front Input Circuit Low:
WHEN MONITORED
While the CAN bus ignition status is in IGN_RUN, the module checks the sensor input ranges.
SET CONDITION
If the module detects that the sensor input is less than 3.4 ± 0.6% of the (R726) Seat Weight Sensor 5 Volt circuit voltage. This DTC will also set if the (R726) Seat Weight Sensor 5 Volt circuit is shorted to ground. However, this condition would prevent communication with the OCM and cause a Lost Communication With OCM DTC to set in other modules.
POSSIBLE CAUSES
- Passenger seat harness improperly routed
- Passenger seat harness wires chaffed, pierced, pinched, partially broken
- Passenger seat harness connector terminals broken, bent pushed out, spread, corroded, contaminated
- (R717) LT - FT seat weight sensor signal circuit shorted to ground
- (R717) LT - FT seat weight sensor signal circuit open
- (R726) seat weight sensor 5 volt circuit open
- Left - front seat weight sensor
- Occupant classification module (OCM)
Diagnostic Test
1. CHECK FOR ACTIVE INTERNAL FAULTS, IGNITION FAULTS, & BATTERY FAULTS IN THE OCCUPANT CLASSIFICATION MODULE (OCM)
NOTE: Ensure the battery is fully charged.
Turn the ignition on.
With the scan tool, read Occupant Classification Module (OCM) DTCs.
Q: Does the scan tool display any active DTCs relating to internal faults, ignition faults, or battery faults?
YES: Diagnose and repair the DTCs.
NO: Go To 2
2. VERIFY THAT DTC B1B79 - PASSENGER SEAT WEIGHT SENSOR 3 - LEFT FRONT INPUT CIRCUIT LOW IS ACTIVE
With the scan tool, read OCM DTCs.
Q: Does the scan tool display active: B1B79 - PASSENGER SEAT WEIGHT SENSOR 3 - LEFT FRONT INPUT CIRCUIT LOW?
YES: Go To 3
NO: Go To 11
3. INSPECT PASSENGER SEAT HARNESS WIRES & CONNECTORS
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION OFF, DISCONNECT THE BATTERY AND WAIT TWO MINUTES BEFORE PROCEEDING.
Using the wiring diagram/schematic as a guide, inspect the Passenger Seat Harness wiring and connectors. Look for chaffed, pierced, pinched, or partially broken wires and broken, bent, pushed out, spread, corroded, or contaminated terminals.
Q: Are any of these conditions present?
YES:
NOTE: Do not attempt to repair the Seat Harness. Replace the Seat Harness if the condition inspecting or testing for is present in the Seat Harness.
Replace the Passenger Seat Harness. Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
NO: Go To 4
4. VERIFY THAT PASSENGER SEAT HARNESS IS ROUTED CORRECTLY
Verify that the Passenger Seat Harness is routed correctly.
Q: Is the Passenger Seat Harness routed correctly?
YES: Go To 5
NO: Reroute the Passenger Seat Harness as necessary. Then, Go To 5
5. CHECK IF MORE THAN ONE PASSENGER SEAT WEIGHT SENSOR DTC IS ACTIVE
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION ON, THEN RECONNECT THE BATTERY.
NOTE: Failure to follow test instructions or aborting the test will cause faults to set when performing the Occupant Classification Module System Verification Test. To prevent faults due to process errors: Verify That All Tests Steps That Led You Here Were Performed As Directed; Verify That The Ignition Is In Run; Wait 30 Seconds After Changing The Seat Weight Before Proceeding To Allow The System To Stabilize; Only Press Scan Tool Buttons When Directed To Do So; & Perform The Occupant Classification Module System Verification Test To Completion.
With the scan tool in OCM, select More Options, select System Tests, and select Occupant Classification Module System Verification Test. Run the test by following the instructions displayed on the scan tool. When the test is complete, wait two minutes, and then proceed as follows.
With the scan tool, read OCM DTCs.
Q: Does the scan tool display any active PASSENGER SEAT WEIGHT SENSOR DTCs?
YES: Go To 6
YES: Only DTC B1B79 Is Active - Go To 7
NO: Other DTCs Present - Diagnose and repair the DTCs.
NO: Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
6. VERIFY SENSOR TORQUE
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION OFF, DISCONNECT THE BATTERY AND WAIT TWO MINUTES BEFORE PROCEEDING.
Verify that all of the Seat Weight Sensor mounting screws are torqued to specification.
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION ON, THEN RECONNECT THE BATTERY.
NOTE: Failure to follow test instructions or aborting the test will cause faults to set when performing the Occupant Classification Module System Verification Test. To prevent faults due to process errors: Verify That All Tests Steps That Led You Here Were Performed As Directed; Verify That The Ignition Is In Run; Wait 30 Seconds After Changing The Seat Weight Before Proceeding To Allow The System To Stabilize; Only Press Scan Tool Buttons When Directed To Do So; & Perform The Occupant Classification Module System Verification Test To Completion.
With the scan tool in OCM, select More Options, select System Tests, and select Occupant Classification Module System Verification Test. Run the test by following the instructions displayed on the scan tool. When the test is complete, wait two minutes, and then proceed as follows.
With the scan tool, read OCM DTCs.
Q: Does the scan tool display any active PASSENGER SEAT WEIGHT SENSOR DTCs?
YES: More Than One PASSENGER SEAT WEIGHT SENSOR DTC Is Active - Perform the Diagnosis/Check - out Procedure For Seat Weight Sensors. Symptom Related Diagnostic Procedures
YES: Only DTC B1B79 Is Active - Go To 7
NO: Other DTCs Present - Diagnose and repair the DTCs.
NO: Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
7. CHECK VOLTAGE OF (R726) SEAT WEIGHT SENSOR 5 VOLT CIRCUIT
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION OFF, DISCONNECT THE BATTERY AND WAIT TWO MINUTES BEFORE PROCEEDING.
Disconnect the Left - Front Seat Weight Sensor connector.
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION ON, THEN RECONNECT THE BATTERY.
Measure the voltage of the (R726) Seat Weight Sensor 5 Volt circuit.
Q: Is the voltage above 4.8 volts?
YES: Go To 8
NO: Go To 10
8. CHECK (R717) LT - FT SEAT WEIGHT SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION OFF, DISCONNECT THE BATTERY AND WAIT TWO MINUTES BEFORE PROCEEDING.
Disconnect the OCM C2 connector.
Measure the resistance of the (R717) LT - FT Seat Weight Sensor Signal circuit between ground and the OCM C2 connector.
Q: Is the resistance below 10k ohms?
YES:
NOTE: Do not attempt to repair the Seat Harness. Replace the Seat Harness if the condition inspecting or testing for is present in the Seat Harness.
Replace the Passenger Seat Harness. Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
NO: Go To 9
9. CHECK (R717) LT - FT SEAT WEIGHT SENSOR SIGNAL CIRCUIT FOR AN OPEN
Measure the resistance of the (R717) LT - FT Seat Weight Sensor Signal circuit between the OCM C2 connector and the Left - Front Seat Weight Sensor connector.
Q: Is the resistance below 5.0 ohms?
YES: Replace the Left - Front Seat Weight Sensor. Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
If DTC B1B79 - PASSENGER SEAT WEIGHT SENSOR 3 - LEFT FRONT INPUT CIRCUIT LOW returns active, replace the OCM. Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
NO:
NOTE: Do not attempt to repair the Seat Harness. Replace the Seat Harness if the condition inspecting or testing for is present in the Seat Harness.
Replace the Passenger Seat Harness. Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
10. CHECK (R726) SEAT WEIGHT SENSOR 5 VOLT CIRCUIT FOR AN OPEN
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION OFF, DISCONNECT THE BATTERY AND WAIT TWO MINUTES BEFORE PROCEEDING.
Disconnect the OCM C2 connector.
Measure the resistance of the (R726) Seat Weight Sensor 5 Volt circuit between the OCM C2 connector and the Left - Front Seat Weight Sensor connector.
Q: Is the resistance below 5.0 ohms?
YES: Replace the OCM. Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
NO:
NOTE: Do not attempt to repair the Seat Harness. Replace the Seat Harness if the condition inspecting or testing for is present in the Seat Harness.
Replace the Passenger Seat Harness. Perform OCS VERIFICATION TEST - VER 1. OCS Verification Test
11. TEST FOR INTERMITTENT CONDITION
With the scan tool, record and erase all DTCs from all Airbag Modules.
If any ACTIVE codes are present they must be resolved before diagnosing any stored codes.
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION OFF, DISCONNECT THE BATTERY AND WAIT TWO MINUTES BEFORE PROCEEDING.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Look for chaffed, pierced, pinched, or partially broken wires and broken, bent, pushed out, spread, corroded, or contaminated terminals.
The following additional checks may assist you in identifying a possible intermittent problem.
Reconnect any disconnected components and harness connector.
WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION ON, THEN RECONNECT THE BATTERY.
With the scan tool, monitor active codes as you work through the following steps.
WARNING: TO AVOID PERSONAL INJURY OR DEATH, MAINTAIN A SAFE DISTANCE FROM ALL AIRBAGS WHILE PERFORMING THE FOLLOWING STEPS.
Wiggle the wiring harness and connectors of the related airbag circuit or component.
If codes are related to the Driver Airbag circuits, rotate the steering wheel from stop to stop.
If only stored codes return, continue the test until the problem area has been isolated.
In the previous steps you have attempted to recreate the conditions responsible for setting the active DTC in question.
Q: Does the scan tool display any ACTIVE DTCs?
YES: Select appropriate symptom from Symptom List.
NO: No problem found at this time. Erase all codes before returning vehicle to customer.