Circuit Description
The inflatable restraint sensing and diagnostic module (SDM) monitors the front end discriminating sensor circuit for front impact detection. The SDM processes the signal provided by the front end discriminating sensor to further support deployment of the air bags. The front end discriminating sensor is an input only to the SDM and does not directly cause air bag deployment. When you first turn the ignition ON, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. The SDM then performs the following continuous diagnostic tests on the deployment loops:
| • | Deployment loop voltage out of range test |
| • | Deployment loop resistance measurement test |
If the voltage out of range tests detects a short to voltage condition, the resistance measurement test for that deployment loop will not be performed.
Conditions for Running the DTC
| • | Ignition voltage is within the normal operating voltage range. |
| • | The SDM monitors the inflatable restraint front end discriminating sensor loop with the ignition ON. |
Conditions for Setting the DTC
The voltage at the discriminating sensor signal input is 0.5 volts or less for 300 milliseconds.
Action Taken When the DTC Sets
| • | The SDM disables the discriminating sensor input. |
| • | The SDM commands ON the AIR BAG warning lamp via Class 2 serial data. |
Conditions for Clearing the DTC
| • | The voltage at the discriminating sensor signal input is greater than .5 volts for 300 milliseconds. |
| • | 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. |
Diagnostic Aids
A short to ground condition in the inflatable restraint front end discriminating sensor loop can cause an intermittent condition. Inspect the inflatable restraint front end discriminating sensor circuits carefully for cutting or chafing. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
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This step checks the inflatable restraint front end discriminating sensor wiring harness connector.
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This step checks the inflatable restraint front end discriminating sensor.
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This step checks the inflatable restraint sensing and diagnostic module (SDM) wiring harness connector.
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This step checks for a short to ground in the inflatable restraint front end discriminating sensor input circuit.
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This step checks for a short to ground in the inflatable restraint front end discriminating sensor return circuit.
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This step determines if there is a short to between the inflatable restraint front end discriminating sensor input and return circuits or if there is a malfunctioning SDM.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the SIR Diagnostic System Check? | -- | Go to Step 2 | |||||||
Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Does the inflatable restraint front end discriminating sensor connector exhibit any signs of corrosion, terminal damage, or poor connections? | -- | Go to Step 3 | Go to Step 4 | |||||||
3 | Replace the inflatable restraint front end discriminating sensor connector. Refer to Connector Repairs . Did you complete the repair? | -- | Go to Step 15 | -- | ||||||
Use the J 39200 Digital Multimeter (DMM) to measure the resistance between the inflatable restraint front end discriminating sensor terminals. Does the resistance measure more than the specified value? | 900 ohms | Go to Step 6 | Go to Step 5 | |||||||
5 | Replace the inflatable restraint front end discriminating sensor. Refer Inflatable Restraint Front End Discriminating Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
Does the SDM wiring harness connector exhibit any signs of corrosion, terminal damage, or poor connections? | -- | Go to Step 7 | Go to Step 8 | |||||||
7 | Replace the SDM wiring harness connector. Refer to Connector Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 15 | -- | ||||||
Use the DMM to measure the resistance between the inflatable restraint front end discriminating sensor input circuit to ground. Does the resistance measure less than the specified value? | OL | Go to Step 9 | Go to Step 10 | |||||||
9 | Locate and repair the short to ground in the inflatable restraint front end discriminating sensor input circuit. Did you complete the repair? | -- | Go to Step 15 | -- | ||||||
Use the DMM to measure the resistance between the inflatable restraint front end discriminating sensor return circuit to ground. Does the resistance measure less than the specified value? | OL | Go to Step 11 | Go to Step 12 | |||||||
11 | Locate and repair the short to ground in the inflatable restraint front end discriminating sensor return circuit. Did you complete the repair? | -- | Go to Step 15 | -- | ||||||
Use the DMM to measure the resistance between the inflatable restraint front end discriminating sensor input circuit and the inflatable restraint front end discriminating sensor return circuit at the SDM. Does the resistance measure less than the specified value? | OL | Go to Step 13 | Go to Step 14 | |||||||
13 | Locate and repair the short between the inflatable restraint front end discriminating sensor input circuit and the inflatable restraint front end discriminating sensor return circuit. Did you complete the repair? | -- | Go to Step 15 | -- | ||||||
14 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Did you complete the repair? | -- | Go to Step 15 | -- | ||||||
15 |
Does the DTC reset? | -- | -- |
