GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Savana 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 Malfunction Indicator Lamp (MIL) Inoperative

Object Number: 550651 Size: SF
Engine Controls Components
Fuses, MIL, PCM, DLC, G101, G103, G201
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

There should always be a steady Malfunction Indicator Lamp (MIL) when the ignition is ON and engine OFF. Battery ignition voltage is supplied to the lamp. The PCM will turn the lamp ON by grounding the MIL control circuit.

Diagnostic Aids

If the engine cranks but will not run, check:

    • Continuous battery-fuse or fusible link for open.
    • PCM ignition fuse for open.
    • Battery Feed circuit to PCM for open.
    • Ignition Feed circuit to PCM for open.
    • Poor connection to PCM.

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

  1. This step will isolate the problem in the MIL control circuit.

    2.

  2. If the Battery Feed, Ignition Feed and diagnostic test circuits have voltage, the PCM connections, the grounds, or the PCM are malfunctioning.

    3.

  3. Refer to the PCM terminal end view in this section for the PCM pin locations of the ground circuits.

    4.

  4. If the fuse/fusible link is open, refer to PCM Wiring Diagram for a complete circuit.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Attempt to start the engine.

Does the engine start?

--

Go to Step 3

Go to Step 6

3

  1. Turn OFF the Ignition.
  2. Disconnect the blue PCM connector.
  3. Turn ON the ignition.
  4. With a fused jumper wire connected to ground, probe the MIL control circuit at the PCM connector.
  5. Observe the MIL.

Is the MIL ON?

--

Go to Step 7

Go to Step 8

4

Check the PCM Ignition Feed and Battery Feed fuses.

Are both of the fuses OK?

--

Go to Step 5

Go to Step 10

5
  1. Turn OFF the ignition.
  2. Disconnect the PCM connectors.
  3. Turn ON the ignition ON.
  4. Probe the PCM harness ignition and battery feed circuits with a test light to ground.

Is the test light ON for both circuits?

--

Go to Step 6

Go to Step 9

6

  1. Check for a malfunctioning PCM ground or a faulty PCM ground connection.
  2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 7

7
  1. Check for a faulty connection at the PCM.
  2. If you find a faulty connection, repair the connection as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 11

8
  1. Check the MIL control circuit for an open.
  2. If the MIL control circuit is open, repair as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 12

9

Locate and repair the open in the PCM battery feed circuit or the PCM ignition feed circuit as necessary.

Is the action complete?

--

Go to Step 16

--

10

Locate and repair the short to ground in the PCM Ignition Feed circuit or the PCM Battery Feed circuit as necessary.

Is the action complete?

--

Go to Step 16

--

11

Replace the PCM.

Important: If the PCM is faulty, the new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 16

--

12
  1. Check the MIL control circuit for a faulty connection at the instrument cluster connector.
  2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 13

13
  1. Remove the instrument cluster.
  2. Inspect the MIL bulb.

Is the bulb OK?

--

Go to Step 15

Go to Step 14

14

Replace the MIL bulb.

Is the action complete?

--

Go to Step 17

--

15

Replace the instrument cluster.

Is the action complete?

--

Go to Step 16

--

16
  1. Using the Scan Tool, select DTC, Clear Info.
  2. Attempt to start the engine.

Does the engine start and continue to run?

--

Go to Step 17

Go to Step 2

17
  1. Allow engine to idle until the normal operating temperature is reached.
  2. Select DTC, Failed This Ign.

Are any DTCs displayed?

--

Go to the Applicable DTC Table

Go to Step 18

18

Using the Scan Tool, select Capture Info, Review Info.

Are any DTCs displayed that have not been diagnosed?

--

Go to the Applicable DTC Table

System OK