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| • | Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Left Roof Rail Air Bag High Circuit | B0016 02 | B0016 0D | B0016 04 | B0016 01 | B0016 0E |
Left Roof Rail Air Bag Low Circuit | B0016 02 | B0016 0D | B0016 04 | B0016 01 | B0016 0E |
During a side or frontal crash of sufficient force the inflatable restraint sensing and diagnostic module (SDM) will allow current to flow through the deployment loop in order to deploy the left roof rail air bag. The SDM performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity and for shorts to ground or voltage. A shorting bar is used within the left roof rail air bag connector which will short together both left roof rail air bag high and low circuits when the connector is disconnected. This will help to prevent unwanted deployment of the air bag during servicing.
Ignition voltage is between 9-16 volts.
The left roof rail air bag circuit is shorted to voltage for 2 seconds.
The left roof rail air bag control circuit is shorted to ground for 2 seconds.
The left roof rail air bag control circuit is open for 2 seconds.
The left roof rail air bag deployment loop resistance is greater than 4.2 Ω for 2 seconds.
The left roof rail air bag deployment loop resistance is less than 1.4 Ω for 2 seconds.
| • | The SDM commands the AIR BAG indicator ON via serial data communications. |
| • | The SIR System is disabled and no deployments are allowed. |
| • | The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used. |
| • | A history DTC will clear once 255 malfunction-free ignition cycles have occurred. |
Note: The following diagnostic aids apply for both current and history DTCs.
An incorrectly installed CPA or incorrectly seated connector can cause a shorting bar to short both control circuits together. Check the connectors and CPAs if a DTC with symptom byte 02 or 0E is set, to ensure the shorting bars are not causing the circuits to be shorted together. Shorting bars are used in the locations listed below:
| • | Left roof rail air bag |
| • | Inline connectors - on the side of the harness connector |
| • | Harness side of the SDM connector |
Terminal fretting or incorrectly seated connector can cause an open/high resistance condition. Check the circuit terminals for fretting or incorrectly seated connector if a DTC with symptom byte 04 or 0D is set.
If the left roof rail air bag has inflated under unexpected conditions and/or DTC with symptom byte 01 is set, check both control circuits for a short to voltage.
Note: Refer to SIR Service Precautions
Inspect all terminals for damage or corrosion when disconnecting connectors. Damage or corrosion in the following requires repair or replacement of the affected component/connector.| • | Left roof rail air bag |
| • | Inline connectors - on the side of the harness connector |
| • | Harness side of the SDM connector |
Note: The connector and connector position assurance (CPA) may seat independently of each other. Both the connector and CPA should seat with an audible and/or tactile click. The CPA isolates the shorting-bars within the connector allowing the deployment circuit to operate properly.
If the condition is intermittent or cannot be duplicated, disconnect the connectors and add Nyogel lubricant 760G. This procedure will correct the high resistance condition due to terminal fretting corrosion.Observe the scan tool Deployment Loop Resistance parameters while moving the harness near each connector listed below. The reading should stay consistently between 1.7 and 4.2 Ω without any drop outs or spikes.
| • | Left roof rail air bag |
| • | Any inline harness |
| • | SDM |
| ⇒ | If the reading is erratic while moving the harness, perform the following: |
| • | Inspect each connector terminal for damage or corrosion and repair as necessary. |
| • | Apply Nyogel lubricant 760G to each connector terminal. |
| • | Insure each connector and CPA is correctly seated. |
Note: When removing connectors inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector. • Left roof rail air bag • SDM • Left roof rail air bag wiring harness connector • SDM wiring harness connector
| ⇒ | If less than the specified range, test for a short between the control circuits, check each connector and CPA to ensure that the shorting bars are lifted. If the circuits and shorting bars tests normal, replace the SDM. |
| • | Left roof rail air bag control circuit terminal 1 |
| • | Left roof rail air bag control circuit terminal 2 |
| ⇒ | If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the SDM. |
| • | Left roof rail air bag control circuit terminal 1 |
| • | Left roof rail air bag control circuit terminal 2 |
| ⇒ | If less than the specified range, test the control circuit for a short to ground. If the circuit tests normal, replace the SDM. |
| ⇒ | If greater than the specified range, test both control circuits terminals for an open/high resistance. If the circuits test normal, replace the SDM. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for SDM replacement, setup, and programming |
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