GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2006 🢒 STS 🢒 Body 🢒 Doors 🢒 Diagnostic System Check - Vehicle

Circuit Description

The ignition mode switch has 2 contact buttons.

The upper button, with a circle indicator on it, that starts the engine if the brake pedal is applied.

The lower button has 2 indicators on it, O and ACC. This button cycles the ignition through the following modes:

    • OFF
        This is the normal state upon entering the vehicle, and can also be reached from any other mode by depressing the button. The O indicator illuminates.
    • Accessory
        This mode can be reached from the Off state by depressing the button. The ACC indicator illuminates.
    • ON with the engine OFF
        This state can be reached from the Off or Accessory modes by depressing the button for about 5-6 seconds. The upper LED illuminates.

Test Description

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

  1. This step ensures that the battery, and the vehicle primary power and ground systems are functioning correctly.

    2.

  2. Lack of communication may be due to a particular malfunction of a serial data circuit. The information in Data Link References will provide a list of modules and the associated data network no communication diagnostic link.

Step

Action

Yes

No

1

Perform the following preliminary inspections:

    • Ensure that the battery is fully charged. Refer to Battery Inspection/Test .
    • Ensure that the battery cables are clean and tight.
    • Inspect for any open fuses.
    • Inspect the easily accessible systems or the visible system components for obvious damage or conditions that could cause the symptom.
    • Ensure that the grounds are clean, tight, and in the correct location.
    • Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories .
    • Search for applicable service bulletins.

Did you find and correct the condition?

System OK

Go to Step 2

2

Install a scan tool.

Does the scan tool power up?

Go to Step 3

Go to Scan Tool Does Not Power Up

3

Turn ON the ignition, with the engine OFF.

Is the NO FOB DETECTED message displayed on the driver information center (DIC)?

Go to Key Fob Not Detected

Go to Step 4

4

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with all of the control modules on the vehicle. Refer to Data Link References for the modules you should expect to observe.

Does the scan tool communicate with all of the expected vehicle control modules?

Go to Step 5

Go to Data Link References

5

Attempt to start the engine.

Does the engine crank?

Go to Step 6

Go to Symptoms - Engine Electrical

6

Attempt to start the engine.

Does the engine start and idle?

Go to Step 7

    • Go to Engine Cranks But Does Not Run for the 3.6L (LY7) engine
    • Go to Engine Cranks But Does Not Run for the 4.4L engine
    • Go to Engine Cranks But Does Not Run for the 4.6L (LH2) engine

7

Important: Do NOT clear any DTCs unless instructed by a diagnostic procedure.

   •  Diagnose the DTCs in the order that the DTCs appear on the scan tool or mis-diagnosis may occur.
   • If multiple powertrain DTCs are stored, diagnose the DTCs in the following order:

  1. Component level DTCs, such as sensor DTCs, solenoid DTCs, and relay DTCs.
  2. System level DTCs, such as misfire DTCs, evaporative emission (EVAP) system DTCs, and fuel trim DTCs.

Advance to the List All DTCs screen on the scan tool.

Does the scan tool display any DTCs?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 8

8

Is the customers concern with inspection/maintenance (I/M) testing?
    • Go to Inspection/Maintenance (I/M) System Check for the 3.6L (LY7) engine
    • Go to Inspection/Maintenance (I/M) System Check for the 4.4L engine
    • Go to Inspection/Maintenance (I/M) System Check for the 4.6L (LH2) engine

Go to Symptoms - Vehicle