1. Turn the ignition switch to the LOCK position.
2. Set the parking brake.
3. Reconnect any connectors or components that were previously disconnected.
4. Turn the ignition switch to the RUN position.
5. Monitor the message center.

Did the message center display any indicators?

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Go to Step 2

Refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gauges and Console

Did the message center display a SECURITY indicator for approximately 5 seconds?

--

Go to Step 4

Go to Step 3

Does the SECURITY indicator flash?

--

Go to Step 4

Go to Step 7

Connect a scan tool to the data link connector.

Can the scan tool be powered up?

--

Go to Step 5

Refer to Scan Tool Does Not Communicate with Class 2 Data Line in Wiring Systems

1. Turn the ignition switch to the RUN position.
2. Use a scan tool in order to inspect for Passlock DTCs.

Does the scan tool display No Communication with Vehicle?

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Refer to Scan Tool Does Not Communicate with Class 2 Data Line in Wiring Systems

Go to Step 6

DTC B2958 may be stored with only a history status. Refer to DTC B2958 Security System Sensor Data Circuit High .

Are there any security system body control module (BCM) DTCs present?

--

Go to the applicable DTC Table

Go to Step 7

Attempt to start the vehicle.

Does the engine crank fast enough to start the vehicle?

--

Go to Step 8

Refer to Starting System Check in Engine Electrical

1. Monitor the scan tool parameter Passlock code from the BCM security list.
2. Attempt to start the vehicle.

Does the scan tool continue to display OPEN for the Passlock code?

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Refer to DTC B2958 Security System Sensor Data Circuit High

Go to Step 9

Does the engine start and run?

--

System OK

Refer to:

• Powertrain On Board Diagnostic (OBD) System Check in Engine Controls-4.3L engine.

Powertrain On Board Diagnostic (OBD) System Check in Engine Controls-4.8L, 5.3L, 6.0L engines.