For 1990-2009 cars
SIR Components
SIR Schematics
SIR Handling Caution
SIR Handling Caution
SIR Handling Caution
Handling ESD Sensitive Parts Notice

### Circuit Description

When you turn the ignition switch to the ON position, the inflatable restraint Sensing and Diagnostic Module (SDM) performs tests in order to diagnose malfunctions. Next, the SDM measures IGNITION 1 and the deployment loop voltages in order to verify normal voltage ranges. Then, the SDM proceeds with the Resistance Measurement test. During one portion of the Resistance Measurement test, the SDM does the following:

• | Grounds the Driver Side Low terminal 10 through an internal current sink.

• | Connects the Driver Side High terminal 9 to an internal constant current source. This current produces proportional voltage drops in the deployment loop.

• | Measures the voltage difference between Driver Side High and Driver Side Low.

• | Calculates the resistance of the driver deployment loop using the measured voltage.

### Conditions for Setting the DTC

• | The driver deployment loop and the passenger deployment loop are not open.

• | The driver deployment loop and the passenger deployment loop are not shorted to voltage.

• | The driver deployment loop is not shorted to ground.

• | The driver deployment loop resistance is more than 3.8 ohms. The driver deployment loop consists of the following components:

- | The Inflatable Restraint steering wheel module.

- | The inflatable restraint steering wheel module coil.

- | The harness wiring of the GRN/RED wire.

- | The harness wiring of the GRN wire.

- | The connector terminal contact.

The Resistance Measurement test checks for this malfunction. This test only occurs once each ignition cycle when IGNITION 1 is within the normal operating voltage range.

### Action Taken When the DTC Sets

• | The SDM sets a diagnostic trouble code.

• | The SDM turns ON the AIR BAG warning lamp.

### Conditions for Clearing the DTC

• | Clear the Current DTC if the resistance of the driver deployment loop is less than 3.8 ohms and the ignition switch is cycled.

• | Clear the History DTC under the following conditions:

- | You use the scan tool in order to clear the DTC.

- | 250 malfunction free ignition cycles have occurred.

When you use the scan tool in order to clear the DTC and the malfunction is still not present, the DTC will not appear until the next ignition cycle.

### Diagnostic Aids

A poor connection can cause an intermittent condition. Check the following for a poor connection:

• | The connector of the inflatable restraint steering wheel module in the steering wheel column at terminal 1 and at terminal 2.

• | The upper connector of the inflatable restraint steering wheel module coil at terminal 1 and at terminal 2.

• | Terminal 9 and terminal 10 of the SDM.

• | The wire to terminal connections in the GRN/RED wire.

• | The wire to terminal connections in the GRN wire.

The diagnostic table directs the technician to note the entry value of DRIVER RESISTANCE. Comparing the value of DRIVER RESISTANCE can help determine if an intermittent condition exists.

If measurements are requested in this table, use J 39200 the Digital Multimeter with the correct terminal adapter J 35616 from the Connector Test Adapter Kit. If a check for a correct connection is requested, refer Testing for Intermittent Conditions and Poor Connections to . If a wire repair, a connector repair, or a terminal J-38125 repair is requested, use the Terminal Wiring Repair Repair Kit, and refer to .

### Test Description

The numbers below refer to steps in the diagnostic table.

1. This test determines the deployment loop resistance that the Sensing and Diagnostic Module (SDM) measures.

2. This test checks for the correct contact and/or for corrosion of the yellow 2-way connector.

3. This test isolates the malfunction to one side of the yellow 2-way connector of the inflatable restraint module near the base of the steering column.

4. This test determines if the malfunction is in the inflatable restraint steering wheel module coil or in the inflatable restraint steering wheel module.

5. This test checks for the correct contact and/or for corrosion of the SDM connector.

6. This test checks for the correct contact and/or for corrosion of the SDM connector.

7. This test determines if the malfunction is in the GRN/RED wire.

8. This test determines if the malfunction is in the GRN wire.

#### DTC B1021 Driver Development Loop Resistance High

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Was the SIR Diagnostic System Check performed? | -- | Go to Step 2 | Go to SIR Diagnostic System Check
2 |

1. Turn the ignition switch to the LOCK position.
2. Connect a scan tool to the data link connector. Follow the directions in the instruction manual of the scan tool.
3. Turn the ignition switch to the ON position.
4. Request the SIR data list display.
5. Read the DRIVER RESISTANCE. Record resistance on the repair order.

Did you record the DRIVER RESISTANCE on the repair order?

--

Go to Step 3

--

3 |

1. Turn the ignition switch to the LOCK position.
2. Disconnect the yellow connectors of the inflatable restraint steering wheel module and of the inflatable restraint IP module. The connectors are near the base of the steering column and behind the IP compartment.
3. Check for the correct connection at terminal 1 and at terminal 2 on the harness side of the yellow connectors of the inflatable restraint steering wheel module at the base of the steering column.

Are the terminals damaged or corroded?

--

Go to Step 4

Go to Step 6

4 | Replace the yellow 2-way harness connector at the base of the steering column. Refer to SIR Connector (Plastic Body and Terminal Metal Pin) Repair Portion of Wiring Repair . Did you replace the yellow 2-way harness connector? | -- | Go to Step 5 | --
5 | Check the connection at terminal D3 and at terminal D4 on the coil side of the 2-way connector of the inflatable restraint steering wheel module. Are the terminals damaged or corroded? | -- | Go to Step 7 | Go to Step 8
6 | Check the connection at terminal D3 and at terminal D4 on the coil side of the 2-way connector of the inflatable restraint steering wheel module. Are the terminals damaged or corroded? | -- | Go to Step 7 | Go to Step 8
7 | Replace the inflatable restraint steering wheel module coil. Refer to Inflatable Restraint Steering Wheel Module Coil Replacement . Did you replace the inflatable restraint steering wheel module coil? | -- | Go to Step 23 | --
8 |

1. Reconnect the yellow connectors of the inflatable restraint steering wheel module and of the inflatable restraint IP module.
2. Turn the ignition switch to the ON position.
3. Using the scan tool, request the SIR data list display. Read the DRIVER RESISTANCE.

Is the DRIVER RESISTANCE more than the specified value?

3.8 ohms

Go to Step 10

Go to Step 9

9 |

1. Turn the ignition switch to the LOCK position.
2. Replace the yellow 2-way harness connector at the base of the steering column. Refer to the SIR Connector (Plastic Body and Terminal Metal Pin) Repair Section Wiring Repair of .

Did you replace the yellow 2-way harness connector?

--

Go to Step 23

--

10 |

1. Turn the ignition switch to the LOCK position.
2. Disconnect the yellow connectors of the inflatable restraint steering wheel module and of the inflatable restraint IP module. The connectors are near the base of the steering column and behind the IP compartment.
3. Connect the J 38715-A to the harness connectors of the inflatable restraint steering wheel module and of the inflatable restraint IP module.
4. turn the ignition switch to the ON position.
5. Using the scan tool, request the SIR data list display. Read the DRIVER RESISTANCE.

Is the DRIVER RESISTANCE more than the specified value?

3.8 ohms

Go to Step 14

Go to Step 11

11 |

1. Turn the ignition switch to the LOCK position.
2. Remove the inflatable restraint steering wheel module from the steering wheel. Refer to Inflatable Restraint Steering Wheel Module Replacement .
3. Disconnect the J 38715-A from the 2-way connector at the base of the steering column.
4. Reconnect the 2-way connector at the base of the steering column.
5. Connect the J 38715-A to the inflator module connector on the steering column.
6. Turn the ignition switch to the ON position.
7. Using the scan tool, request the SIR data list display. Read the DRIVER RESISTANCE.

Is the DRIVER RESISTANCE more than the specified value?

3.8 ohms

Go to Step 13

Go to Step 12

12 |

1. Turn the ignition switch to the LOCK position.
2. Replace the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .

Have you replaced the inflatable restraint steering wheel module?

--

Go to Step 23

--

13 |

1. Turn the ignition switch to the LOCK position.
2. Replace the inflatable restraint steering wheel module coil. Refer to Inflatable Restraint Steering Wheel Module Replacement .

Have you replaced the Sensing and Diagnostic Module (SDM)?

--

Go to Step 23

--

14 |

1. Turn the ignition switch to the LOCK position.
2. Disconnect the Sensing and Diagnostic Module (SDM).
3. Disconnect the J 38715-A .
4. Check for the correct connection at terminal 9 and at terminal 10 on the harness side of the SDM connector.

Is the SDM harness connector damaged or corroded?

--

Go to Step 15

Go to Step 17

15 | Replace the SDM harness connector. Refer to SIR Connector (Plastic Body and Terminal Metal Pin) Repair portion of Wiring Repair . Did you replace the SDM harness? | -- | Go to Step 16 | --
16 | Check for the correct connection at terminal 9 and at terminal 10 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 18 | Go to Step 23
17 | Check for the correct connection at terminal 9 and at terminal 10 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 18 | Go to Step 19
18 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Did you replace the SDM? | -- | Go to Step 23 | --
19 |

1. Zero the J 39200 .
2. Measure the resistance from the SDM harness connector terminal 9 to the 2-way harness connector terminal 2 of the inflatable restraint steering wheel module.

Is the resistance reading within specified values?

0-0.5 ohms

Go to Step 21

Go to Step 20

20 | Repair the high resistance in the GRN/RED wire. Is the circuit repair complete? | -- | Go to Step 23 | --
21 |

1. Zero the J 39200 .
2. Measure the resistance from the SDM harness connector terminal 10 to the 2-way harness connector terminal 1 of the inflatable restraint steering wheel module.

Is the resistance reading within specified values?

0-0.5 ohms

Go to Sensing and Diagnostic Module Integrity Check

Go to Step 22

22 | Repair high resistance in the GRN wire. Is the circuit repair complete? | -- | Go to Step 23 | --
23 |

1. Reconnect all the SIR system components.
2. Verify that all the components are correctly mounted.

Did you reconnect and correctly mount all the SIR components?

--

Go to Step 24

--

24 | Clear the SIR diagnostic trouble codes. Did you clear the SIR diagnostic trouble codes? | -- | Go to SIR Diagnostic System Check | --