For 1990-2009 cars

### Circuit Description

When the ignition switch is turned On and during vehicle operation, the SDM performs tests to detect system faults. One test the SDM performs is to monitor the passenger side high circuit and passenger side low circuit voltage difference. By monitoring the voltage, the SDM is able to detect when loop voltage is not between 2.4 and 6.0 volts.

### Conditions for Setting the DTC

DTC B0018 can set when the passenger loop is out of range. The following conditions must be met to set this DTC.

• | Ignition voltage is present at the SDM and continuous.

• | The passenger deployment loop voltage is over 6 volts or under 2.4 volts and loop resistance is under 6 ohms.

• | Fault needs to only be present for less than half a second or five consecutive sample readings.

### Action Taken When the DTC Sets

• | When this fault is detected a current DTC will be set.

• | The air bag light will be turned On.

• | Passenger loop resistance test will be disabled.

### Diagnostic Aids

When attempting to diagnose an intermittent passenger loop fault, use the scan tool to monitor current DTCs. Wiggle the wires and check connections while watching for a current DTC to appear and/or disappear on Scan tool.

Always start diagnosis of SIR DTCs with an inspection of wiring and components for visible damage.

A short to ground in circuits 1403 or 1404 could cause this DTC.

A short between circuits 1403 or 1404 and another vehicle circuit could cause this DTC.

Always perform the SIR Diagnostic System Check before using this chart.

When measurements are requested in this chart, use SA 91114NE digital multimeter with correct terminal adapter from SA 9206Z. When a check for proper connection is requested, refer to Intermittent and Poor Connections in this manual. When a wire connector or terminal repair is requested, use the proper repair parts and refer to Wiring Repair in the service manual.

Step | Action | Yes | No
--- | --- | --- | ---
1 |

• | Ignition switch Off.

• | Disconnect the passenger yellow I/P top cover.

• | Check for corroded or damaged harness terminals.

Are the terminals OK?

Go to Step 3

Go to Step 2

2 |

• | Refer to "Wiring and Connector Repair" procedure in this service manual.

• | Replace terminal(s) with appropriate SIR lead kit.

Are the repairs complete?

Go to Step 14

--

3 |

• | Ignition switch Off.

• | Connect SA9409-Z SIR load tool to passenger module harness connector.

• | Ignition switch On.

Is DTC B0018 current?

Go to Step 4

Go to Step 13

4 |

• | Ignition switch Off.

• | Disconnect SA9409-Z SIR load tool.

• | Disconnect SDM connector.

• | Measure resistance of circuit 1403 to ground.

Does the digital multimeter display OL (infinite)?

Go to Step 6

Go to Step 5

5 |

• | Ignition switch Off.

• | Repair short to ground in circuit 1403.

Are the repairs complete?

Go to Step 14

--

6 |

• | Ignition switch Off.

• | Measure resistance from circuit to ground.

Does the digital multimeter display OL (infinite)?

Go to Step 8

Go to Step 7

7 |

• | Ignition switch Off.

• | Repair short to ground in circuit 1404.

Are the repairs complete?

Go to Step 14

--

8 |

• | Ignition switch On.

• | With SDM connector and passenger inflator disconnected, measure the voltage between circuit 1403 and ground.

Does the digital multimeter display less than 1 volt?

Go to Step 10

Go to Step 9

9 |

• | Ignition switch Off.

• | Repair short to B+ in circuit 1403.

Go to Step 14

--

10 |

• | Ignition switch On.

• | With SDM connector and passenger inflator disconnected, measure the voltage between circuit 1404 and the ground.

Does the digital multimeter display less than 1 volt?

Go to Step 12

Go to Step 11

11 |

• | Ignition switch Off.

• | Repair short to B+ in circuit 1404.

Are the repairs complete?

Go to Step 14

--

12 |

• | Ignition switch Off.

• | Replace the SDM.

Are the repairs complete?

Go to Step 14

--

13 |

• | Ignition switch Off

• | Replace the passenger inflator module.

Are the repairs complete?

Go to Step 14

--

14 |

• | Reconnect all components.

• | Clear DTCs.

Was the Diagnostic System Check performed after repair?

--

Go to Step 15

15 | Perform the Diagnostic System Check. | -- | --

Important: Air bag telltale will remain On after the same DTC appears twice and is stored in memory as a history code. If the air bag telltale is On, the DTC can be a current or history code.