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

### Circuit Description

When you first turn the ignition switch to the ON position, the inflatable restraint Sensing and Diagnostic Module (SDM) performs tests to diagnose malfunctions within itself. Nest the SDM measures IGNITION 1 and the deployment loop voltages to verify they are within their respective 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 and passenger deployment loops are not open.

• | The driver and passenger deployment loops 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 (SIR) 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 when 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 issue a scan tool CLEAR CODES command.

- | 250 malfunction free ignition cycles have occurred.

When you issue a scan tool CLEAR CODES command and the malfunction is still not present, the DTC will not reappear until the next ignition cycle.

### Diagnostic Aids

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

• | The inflatable restraint steering wheel module steering wheel column connector terminal 1 and terminal 2.

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

• | The SDM terminal 9 and terminal 10.

• | 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 be helpful in determining if an intermittent condition exists.

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

### Test Description

Numbers below refer to step numbers on the diagnostic table.

1. This test determines the deployment loop resistance measured by the inflatable restraint Sensing and Diagnostic Module (SDM).

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

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

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

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

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

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

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

#### DTC B1021 Driver Development Loop Resistance High

Step | Action | Value(s) | 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 deployment loop resistance DRIVER RESISTANCE. Record resistance on the repair order.

Did you read and record DRIVER RESISTANCE on the repair order?

--

Go to Step 3

--

3 |

1. Turn the ignition switch to the LOCK position.
2. Disconnect the inflatable restraint steering wheel and inflatable restraint IP modules yellow connectors. These are located near the base of the steering column and behind the IP compartment.
3. Check for proper connection at terminal D3 and terminal D4 on the harness side of the inflatable restraint steering wheel module 2-way connector 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 for proper connection at terminal D3 and terminal D4 on the inflatable restraint steering wheel module coil side of the 2-way connector. Are the terminals damaged or corroded? | -- | Go to Step 7 | Go to Step 8
6 | Check for proper connection at terminal D3 and terminal D4 on the inflatable restraint steering wheel module coil side of the 2-way connector. 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 inflatable restraint steering wheel and inflatable restraint IP module yellow connectors.
2. Turn the ignition switch to the ON position.
3. Using the scan tool, request the SIR data list display. Read the driver deployment loop resistance DRIVER RESISTANCE.

Is DRIVER RESISTANCE more than 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 SIR Connector (Plastic Body and Terminal Metal Pin) Repair Section of Wiring Repair .

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 inflatable restraint (SIR) steering wheel and inflatable restraint IP modules yellow connectors. These are located near the base of the steering column and behind the IP compartment.
3. Connect the J 38715-A to the inflatable restraint steering wheel and inflatable restraint IP module harness connectors.
4. turn the ignition switch to the ON position.
5. Using the scan tool, request the SIR data list display. Read the driver deployment loop resistance DRIVER RESISTANCE.

Is the DRIVER RESISTANCE more than the specified value?

3.8ohms

Go to Step 14

Go to Step 11

11 |

1. Turn the ignition switch to the LOCK position.
2. Remove the inflatable restraint (SIR) 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 deployment loop resistance DRIVER RESISTANCE.

Is the DRIVER RESISTANCE more than the specified value?

3.8ohms

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 inflatable restraint Sensing and Diagnostic Module (SDM)?

--

Go to Step 23

--

14 |

1. Turn the ignition switch to the LOCK position.
2. Disconnect the inflatable restraint Sensing and Diagnostic Module (SDM).
3. Disconnect the J 38715-A .
4. Check for proper connection at terminal 9 and 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 proper connection at terminal 9 and terminal 10 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 18 | Go to Step 23
17 | Check for proper connection at terminal 9 and 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 inflatable restraint steering wheel module 2-way harness connector terminal 2.

Is the resistance reading within specified values?

0-0.5ohms

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 inflatable restraint steering wheel module 2-way harness connector terminal 1.

Is the resistance reading within specified values?

0-0.5ohms

Go to 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 properly mounted.

Did you reconnect and properly 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 | --