For 1990-2009 cars

### Circuit Description

The SDM contains a sensing device that converts the vehicle velocity changes to an electrical signal. The electrical signal is generated by the SDM and compared to a value stored in memory. When the generated signals exceed the stored values, the SDM deploys the air bags and stores a DTC in its memory.

### Conditions for Setting the DTC

DTC B0051 is set when the SDM commands the inflators to deploy. The following conditions must be met to set this DTC.

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

• | The SDM detects a frontal crash, up to 30 degrees off the center line of the vehicle.

• | Crash was of sufficient force to warrant deployment of air bags.

### Action Taken When the DTC Sets

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

• | The air bag light will be turned On.

• | DTC will be latched into the SDM's memory.

### Diagnostic Aids

Always start the diagnosis of SIR DTCs with an inspection of vehicle, including its wiring and SIR components for visible damage.

Always replace SDM's with DTC B0051 set, only after all collision repairs have been completed.

Important: DTC B0051 is a latched code and cannot be cleared from the SDM memory.

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

Caution: Be careful when you handle a sensing and diagnostic module (SDM). Do not strike or jolt the SDM. Before applying power to the SDM:

• | Remove any dirt, grease, etc. From the mounting surface.

• | Position the SDM horizontally on the mounting surface.

• | Tighten all of the SDM fasteners and SDM bracket fasteners to the specified torque value.

Failure to follow the correct procedures could cause air bag deployment, personal injury, or unnecessary SIR system repairs.

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

• | Ignition switch Off.

• | Inspect the vehicle for deployed air bags.

Have the air bags been deployed?

Go to Step 3

Go to Step 2

2 | Inspect the front of the vehicle a and undercarriage for signs of impact. Are there signs of impact? | Go to Step 5 | Go to Step 4
3 |

• | Ignition switch Off.

• | Replace coil assembly.

• | Replace the driver inflator module.

• | Replace the passenger inflator module.

• | Replace all other damaged components.

Are the repairs complete?

Go to Step 6

--

4 |

• | Ignition switch Off.

• | Replace the SDM.

Are the repairs complete?

Go to Step 6

--

5 |

• | Refer to Repairs and Inspections Required in an Accident procedure in this service manual.

• | Replace the SDM.

Are the repairs complete?

Go to Step 6

--

6 |

• | Reconnect all components.

• | Clear all DTCs.

Was Diagnostic System Check performed after repair?

--

Go to Step 7

7 | 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.