GM Service Manual Online
For 1990-2009 cars only

Object Number: 491232  Size: MF
Theft Deterrent System Components
Theft Deterrent Passlock ™ Lock Cylinder

Circuit Description

The body control module (BCM) will read an analog voltage from the Passlock™ sensor. Based on an internal reference, the BCM will determine if the measured voltage is in one of the following conditions:

    • Open
    • Shorted to ground
    • A valid code
    • A tamper code

There are 10 possible valid code combination. The BCM will only recognize the last learned valid code.

Conditions for Running the DTC

The ignition switch is cycled to CRANK and released to ON.

Conditions for Setting the DTC

    • The ignition switch is ON.
    • The BCM signal input is greater than 4.9 volts for 1 second after turning the ignition switch to the CRANK position.

Action Taken When the DTC Sets

    • If the DTC sets during cranking, the car will not start or will start with the theft indicator on continuously.
    • If the DTC sets while the engine is running, the car will start on future attempts and the theft indicator flashes.
    • The SERVICE VEHICLE SOON indicator illuminates.

Conditions for Clearing the DTC

    • Current DTCs will clear after one ignition cycle if the malfunction is no longer present.
    • All of the BCM history codes will be cleared after 100 ignition cycles (from OFF to ON) with no current codes active during the 100 ignition cycles.

Diagnostic Aids

    • If the malfunction occurred during engine ON, the vehicle will start on future attempts.
    • If the malfunction occurred during engine crank, the car won't start or will start with the security indicator illuminated.
    • If the malfunction occurred during engine crank, this DTC may not set.
    • Inspect for a poor connection at the Passlock™ sensor and BCM.
    • If the DTC is a history DTC, the problem may be intermittent. Perform the test shown while wiggling the wiring and connectors. This will cause the malfunction to appear.

Test Description

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

  1. Tests for proper operation of the circuit in the high voltage range.

  2. Tests for proper operation of the circuit in the low voltage range.

  3. Tests for high resistance or an open in the battery voltage circuit.

  4. Tests for a short to voltage, a high resistance, or an open in the signal circuit.

  5. Tests for high resistance or an open in the ground circuit.

Step

Action

Value(s)

Yes

No

1

Did you perform the Theft Deterrent (VTD) Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Theft Deterrent

2

  1. Install a scan tool.
  2. Momentarily rotate the ignition switch to CRANK (do not start the vehicle).
  3. Release the ignition switch to ON.
  4. With a scan tool, observe the Passlock™ Data Voltage in the Body Control Module Security Data list.

Does the scan tool indicate that the Passlock Data Voltage is within the specified range?

0.4-4.9v

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the Passlock™ sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool observe the Passlock™ Data Voltage in the Body Control Module Security Data list.

Does the scan tool indicate that the Passlock™ Data Voltage is greater than the specified value?

4.9v

Go to Step 4

Go to Step 9

4

  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the signal circuit of the Passlock™ sensor and the ground circuit of the Passlock™ sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool observe the Passlock™ Data Voltage in the Body Control Module Security Data list.

Does the scan tool indicate that the Passlock™ Data Voltage is less than the specified value?

0.4v

Go to Step 5

Go to Step 7

5

  1. Disconnect the fused jumper wire.
  2. Measure the voltage between the battery voltage circuit of the Passlock™ sensor and the ground circuit of the Passlock™ sensor.

Does the voltage measure less than the specified value?

12.0v

Go to Step 6

Go to Step 11

6

Test the battery voltage circuit of the Passlock™ sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 9

7

Test the signal circuit of the Passlock™ sensor for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 8

8

Test the ground circuit of the Passlock™ sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 9

9

Inspect for poor connections at the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

10

Replace the body control module. Refer to Body Control Module Replacement in Body Control Systems.

Important: Perform the set up procedure for the body control module .

Did you complete the replacement?

--

Go to Step 14

--

11

Inspect for poor connections at the Passlock ™ sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

12

Replace the Passlock™ sensor. Refer to Ignition Lock Cylinder Replacement - On Vehicle in Steering Wheel and Column.

Did you complete the replacement?

--

Go to Step 13

--

13

Perform the Passlock™ learn procedure. Refer to Programming Replacement Lock Cylinder, Body Control Module or Powertrain Control Module .

Is the repair complete?

--

Go to Step 14

--

14

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition
  3. Momentarily rotate the ignition switch to CRANK (do not start the vehicle).
  4. Release the ignition switch to ON.
  5. Select the body control module display DTCs function on the scan tool.

Does the DTC reset?

--

Go to Step 3

Go to Step 15

15

Attempt to start the vehicle.

Does the engine start and run?

--

System OK

Go to Step 3