For 1990-2009 cars

### Circuit Description

When the ignition switch is turned to ON, the sensing and diagnostic module (SDM) will perform a turn-on test to diagnose critical malfunctions within the SDM itself.

At this time, the SDM will establish communication with the passenger presence detection (PPD)/seat belt reminder (SBR)and the PPD/SBR will respond to the SDM by commanding the passenger air bag OFF indicator On for five seconds.

The SDM monitors the PPD/SBR status (occupied, not occupied, seated, defect) cyclically. These 4 messages should transmit every 1.2 seconds to the SDM.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1407 PPD/SBR Communication Error

### Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

### Conditions for Setting the DTC

A communication error occurs between the SDM and the PPD sensor.

### Action Taken When the DTC Sets

The SDM commands the air bag indicator ON.

### Conditions for Clearing the DTC

Caution: The sensing and the diagnosis module (SDM) can maintain sufficient voltage to deploy the airbags and pretensioners for up to 1 minute after the ignition has been turned OFF and the fuse has been removed. If the airbags and pretensioners are not disconnected, do not begin service until one minute has been passed after disconnecting power to the SDM. Failure to do so may cause personal injury.

Caution: Do not strike or jolt the inflatable restraint sensing and diagnostic module (SDM). Before applying power to the SDM, make sure that it is securely fastened with the arrow facing toward the front of the vehicle. Failure to observe the correct installation procedure could cause SIR deployment, personal injury, or unnecessary SIR system repairs.

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Caution: Refer to Sensing and Diagnostic Module Handling Caution in the Preface section. Caution: Refer to Sensing and Diagnostic Module Voltage after Ignition is Turned Off Caution in the Preface section. Schematic Reference: SIR Schematics Connector End View Reference: SIR Connector End Views
1 | Did you perform a Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Confirm that the ignition switch is OFF.
2. Visually inspect the connector and wiring of the passenger presence detection (PPD) sensor and the sensing and diagnostic module (SDM).

Is the wiring OK?

--

Go to Step 4

Go to Step 3

3 | Replace the air bag wiring. Did you complete the replacement? | -- | Go to Step 7 | --
4 |

1. Confirm that the ignition switch is OFF.
2. Replace the PPD sensor.
3. Use the scan tool to clear the DTCs.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the text.

Did DTC B1407 set again?

--

Go to Step 6

Go to Step 7

5 | Replace the air bag wiring. Did you complete the replacement? | -- | Go to Step 7 | --
6 | Replace the SDM. Did you complete the replacement? | -- | Go to Step 7 | --
7 |

1. Reconnect all SIR system components.
2. Verify that all components, connectors, and connector position assurances (CPAs) are properly mounted.
3. Use the scan tool to clear the DTCs.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the text.

Does the DTC reset?

Go to Step 2

System OK