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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 Eldorado 🢒 Restraints 🢒 SIR 🢒 DTC B1135 Discr. Sensor Closed or Short to GND

Object Number: 585662 Size: MF
SIR Components
SIR Schematics
SIR Handling Caution
Handling ESD Sensitive Parts Notice

Circuit Description

When you first turn ON the ignition, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. Then the SDM proceeds to continuous monitoring. The SDM contains a resistor network connected to 5 volts, ground, and to the SDM front end sensor feed. The 1.0 K ohms resistor in the inflatable restraint front end discriminating sensor parallel to the normally open switch provides a parallel path to ground. This causes a specified percentage of voltage in order to appear at the SDM front end sensor feed input. The SDM monitors this voltage in order to detect shorts to ground or a closed discriminating sensor.

Conditions for Running the DTC
    • The SDM is configured for an inflatable restraint front end discriminating sensor.
    • Ignition 1 voltage is within the normal operating voltage range.
    • Front end discriminating sensor input circuit is not shorted to ground.

Conditions for Setting the DTC

The voltage at front end discriminating sensor input terminal is less than or equal to 0.7 volts for 500 milliseconds.

Action Taken When the DTC Sets

The SDM commands ON the AIR BAG warning lamp via Class 2 serial data.

Conditions for Clearing the DTC
    • The voltage at front end sensor input is more than 0.7 volts for 500 milliseconds.
    • You can issue a CLEAR CODES command
    • A history DTC will clear once 250 malfunction free ignition cycles have occurred

Diagnostic Aids

The following can cause an intermittent condition:

    • A short to ground in the inflatable restraint front end discriminating sensor input circuit.
    • Cutting or chafing of front end discriminating sensor input circuit.

If any of the above conditions are found 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:

  1. This test checks for a malfunctioning discriminating sensor.

    2.

  2. This test checks for a short-to-ground front end discriminating sensor input circuit.

DTC B1135 Discriminating Sensor Circuit Closed or Short to Ground

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - SIR

2
  1. Turn OFF the ignition.
  2. Disconnect inflatable restraint front end discriminating sensor connector.
  3. Inspect the wiring harness in-line connector for the following conditions:
    4. • Corrosion
    • Terminal damaged
    • Poor connections/terminal tension
  4. If any of the above conditions are found refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Does connector exhibits any signs of corrosion, terminal damaged, or poor connections?

--

Go to Step 3

Go to Step 4

3

Replace the wiring harness side of in-line connector. Refer to Connector Repairs in Wiring Systems.

Did you complete the replacement?

--

Go to Step 8

--

4

  1. With front end discriminating sensor still disconnect.
  2. Use the J 39200 DMM and measure the resistance between the sensor input and sensor ground.

Does the resistance measure greater than the specified value?

950 ohms

Go to Step 6

Go to Step 5

5

Replace the inflatable restraint front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement .

Did you complete the replacement?

--

Go to Step 8

--

6

  1. Disconnect the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  2. Use the J 39200 and measure the resistance between front end sensor connector input circuit and a known good ground.

Does the resistance measure less than the specified value?

OL

Go to Step 7

Go to Step 8

7

Locate and repair the short to ground in front end sensor input circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 8

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8
  1. Reconnect all SIR components. Refer to Enabling the SIR System .
  2. Verify that all components, connectors and CPAs are properly mounted.
  3. Use the scan tool in order to Clear the DTCs.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Did you complete the action?

--

Go to Diagnostic System Check - SIR

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