B1790
DTC B1790
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC B1790
- Loss of SIR Communications
Circuit/System Description
The passenger presence system (PPS) communication circuit consists of the sensing and diagnostic module (SDM) and the PPS module. The SDM monitors the PPS communication circuit. If the SDM detects a malfunction within the PPS communication circuit, a DTC will be set.
Conditions for Running the DTC
Ignition voltage is between 9-16 volts.
Conditions for Setting the DTC
Any of the following conditions exist for 2 seconds:
B1790
* The SDM circuit is shorted.
* The SDM circuit is open.
* SDM malfunction.
* Occupant classification module malfunction.
Action Taken When the DTC Sets
* The SDM commands the AIR BAG indicator ON.
* The SIR System is disabled and no deployments are allowed.
Conditions for Clearing the DTC
* The condition for setting the DTC no longer exists.
* A history DTC will clear once 100 malfunction-free ignition cycles have occurred.
Reference Information
Schematic Reference
SIR Schematics ([1][2]Air Bag Systems)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
SIR System Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Connector Repairs (Connector Repairs)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information.
Circuit/System Testing
Important: Refer to SIR Service Precautions (Technician Safety Information).
When removing connectors, inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector:
* The front end sensor
* The SDM module
* The front end sensor wiring harness connector
* The SDM wiring harness connector
1. Ignition OFF, disconnect the harness connector at the SDM and the appropriate sensor.
2. Ignition ON, test for less than 1 volt between the signal circuit terminal 12 and ground.
• If greater than the specified range, repair the circuit for a short to voltage.
3. Ignition ON, test for less than 1 volt between the low reference circuit terminal 13 and ground.
• If greater than the specified range, repair the circuit for a short to voltage.
4. Test for infinite resistance between the signal circuit terminal 12 and ground.
• If less than infinite resistance, repair the circuit for a short to ground.
5. Test for less than 1 ohm between PPS module terminal 11 and SDM harness connector terminal 12.
• If greater than the specified range, repair the circuit for an open/high resistance.
6. Test for less then 1 ohm between PPS module terminal 12 and SDM harness connector terminal 13.
• If greater than the specified range, repair the circuit for an open/high resistance.
7. If all circuits test normal, replace the occupant classification module.
8. Reconnect all SIR components. Ignition ON, with a scan tool clear and check for DTCs.
• If the DTC returns and is current, replace the SDM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Inflatable Restraint Front End Sensor Replacement (Inflatable Restraint Front End Sensor Replacement)
* Inflatable Restraint Side Impact Sensor Replacement (Front) (Inflatable Restraint Side Impact Sensor Replacement (Front))Inflatable Restraint Side Impact Sensor Replacement (Rear) (Inflatable Restraint Side Impact Sensor Replacement (Rear))
* SIR/SRS Wiring Repairs (SIR/SRS Wiring Repairs)
* Control Module References (Programming and Relearning) for SDM replacement, setup, and programming