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

### Circuit Description

When you first turn the ignition switch to the RUN position, the inflatable restraint Sensing and Diagnostic Module (SDM) performs tests to diagnose critical malfunctions within itself. Upon passing these tests IGNITION POSITIVE VOLTAGE, 23VLR and the deployment loop voltages are measured to make sure they are within their respective normal voltage ranges. The SDM monitors the voltages at DRIVER LOW terminal 3 and PASSENGER LOW terminal 4 to detect shorts to ground in the inflator module circuits. The service wait time is 10 minutes. Refer to ENABLE/DISABLE procedures.

### Conditions for Setting the DTC

• | The driver and passenger deployment loops are not open.

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

• | The voltage at DRIVER LOW terminal 3 is more than 3.3 volts.

• | The voltage at PASSENGER LOW terminal 4 is less than 3.3 volts for 500 milliseconds.

The following tests check for this DTC. These tests occur when IGNITION 1 is within the normal operating voltage range.

• | POWER-ON-When the malfunction is detected in this test, the RESISTANCE MEASUREMENT test will not be performed.

• | CONTINUOUS MONITORING

### Action Taken When the DTC Sets

• | The SDM sets DTC B1018 and also DTC B1071.

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

### Conditions for Clearing the MIL/DTC

DTC B1018 is a latched code. You cannot clear a latched code. Repair the malfunction that set this DTC before you replace the SDM.

### Diagnostic Aids

A short to ground in the inflatable restraint IP module circuit can cause an intermittent condition. A DTC B1018 would be accompanied by DTC B1071. Inspect CKT 1403 and CKT 1404 carefully for cut or chafed wires. Wiring pigtail damage requires replacement of the inflatable restraint IP module. A careful inspection of the circuits and components indicated on the DTC B1018 table is essential in order to prevent damage to the replacement inflatable restraint Sensing and Diagnostic Module (SDM). The diagnostic table directs the technician to note the entry value of PASSENGER SENSELO. Comparing the value of PASSENGER SENSELO can be helpful in determining if an intermittent condition exists.

When measurements are requested in this table, use the J 39200 DMM with the correct terminal adapter from the J 35616 Connector Test Adapter Kit. When an inspection for proper connection is requested, refer to Testing for Electrical Intermittents in Wiring Systems. When a wire, connector or terminal repair is requested, use the J-38125 Terminal Repair Kit and refer to Wiring Repairs in Wiring Systems.

### Test Description

The numbers below refer to the step numbers on the diagnostic table:

1. This test determines the passenger low voltage measured by the inflatable restraint Sensing and Diagnostic Module (SDM). A reading of 3.3 V or more indicates that an intermittent condition may exist.

2. This test isolates the malfunction to one side of the inflatable restraint I/P module yellow 2-way connector.

3. This test determines whether the malfunction is in CKT 1403.

4. This test determines whether the malfunction is in CKT 1404.

#### DTC B1018 Passenger Deployment Loop Short to Ground

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Notice: When DTC B1018 or B1024 has been set it is necessary to replace the inflatable restraint Sensing and Diagnostic Module (SDM). Setting DTC B1018 or B1024 will also cause DTC B1071 to set. When a scan tool clear codes command is issued and the malfunction is no longer present, DTC B1018 or B1024 and DTC B1071 will remain current. Make sure that the short to ground condition is repaired prior to installing a replacement SDM to avoid damaging the SDM.
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 OFF position.
2. Connect a scan tool to the DLC.
3. Turn the ignition switch to the RUN position.
4. Request the SIR data list display.
5. Read and record on the repair order the passenger low voltage PASSENGER SENSELO.

Is PASSENGER SENSELO less than the specified value?

3.3 V

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the inflatable restraint steering wheel and I/P module yellow 2-way connectors at the base of the steering column and above the RH sound insulator.
3. Connect J 38715-A SIR Driver/Passenger Load Tool to the harness connectors.
4. Turn the ignition switch to the RUN position.
5. Using the scan tool, request the SIR data list display.
6. Read the passenger low voltage PASSENGER SENSELO.

Is PASSENGER SENSELO less than the specified value?

3.3 V

Go to Step 5

Go to Step 4

4 |

1. Turn the ignition switch to the OFF position.
2. Inspect the inflatable restraint I/P module pigtail for damage and proper routing.
3. Replace the inflatable restraint I/P module. Refer to Inflatable Restraint Instrument Panel Module Replacement .

Are the repairs complete?

--

Go to Step 10

--

5 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the inflatable restraint Sensing and Diagnostic Module (SDM).
3. Disconnect the J 38715-A .
4. Measure the resistance on the SDM harness connector from terminals 1 to 6 (ground).

Is the resistance less than the specified value?

OL

Go to Step 6

Go to Step 7

6 | Repair a short-to-ground condition in CKT 1403. Are the repairs complete? | -- | Go to Step 10 | --
7 | Measure the resistance on the SDM harness connector from terminals 4 to 6 (ground). Is the resistance less than the specified value? | OL | Go to Step 8 | Go to Sensing and Diagnostic Module Integrity Check
8 | Repair a short-to-ground condition in CKT 1404. Are the repairs complete? | -- | Go to Step 10 | --
9 | An intermittent short-to-ground condition caused DTC B1018 to set. Use the Diagnostic Aids for DTC B1018 and this table to find the intermittent short-to-ground. Has the intermittent short-to-ground been found and repaired? | -- | Go to Step 10 | --
10 |

1. Reconnect all the SIR system components, make sure all the components are properly mounted.
2. Turn the ignition switch to the RUN position.
3. Make sure PASSENGER SENSELO is more than the specified value.
4. Replace the inflatable restraint Sensing and Diagnostic Module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .

Have all the SIR components been reconnected and properly mounted?

3.3 V

Go to SIR Diagnostic System Check

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