GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Terraza 🢒 Engine 🢒 Engine Controls - 3.5L (LX9) 🢒 Malfunction Indicator Lamp (MIL) Always On

Circuit Description

Battery positive voltage is supplied directly to the malfunction indicator lamp (MIL). The powertrain control module (PCM) turns the MIL ON by grounding the MIL control circuit.

Diagnostic Aids

If the problem is intermittent, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step determines if the condition is with the MIL control circuit or the PCM.

Step

Action

Yes

No

Schematic Reference: Instrument Cluster Schematics in Instrument Panel, Gages, and Console or Engine Controls Schematics

Connector End View Reference: Instrument Panel, Gages, and Console Connector End Views in Instrument Panel, Gages, and Console or Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM).
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the malfunction indicator lamp (MIL).

Is the MIL illuminated?

Go to Step 3

Go to Step 5

3
  1. Remove the instrument panel cluster (IPC). Refer to Instrument Panel Assembly Replacement in Instrument Panel, Gages, and Console.
  2. Test the MIL control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4

Replace the IPC. Refer to Instrument Panel Assembly Replacement in Instrument Panel, Gages, and Console.

Did you complete the replacement?

Go to Step 6

--

5

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 6

--

6
  1. Turn the ignition OFF for 30 seconds.
  2. Start the engine.

Does the vehicle operate correctly without any MIL illumination?

Go to Step 7

Go to Step 2

7

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK