LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Buick >> 2004 >> Century Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls (DTC P0506 To P1640) >> Engine Controls Diagnosis >> DTC P0650 >> Test Description
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Test Description

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

  1. 5:  This step tests for a short to ground in the MIL control circuit. With the powertrain control module (PCM) disconnected and the ignition ON, the MIL should be OFF.
  2. 6:  This step tests for a short to voltage on the MIL control circuit. With the fuse removed, there should be no voltage on the MIL control circuit.
DTC P0650

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Controls Connector End Views  or  Powertrain Control Module (PCM) Connector End Views 
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Verify whether the instrument cluster is operational. If the instrument panel (IP) is completely inoperative, refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gages and Console.
  2. Command the MIL ON and OFF with a scan tool.
Does the MIL turn ON and OFF when commanded with a scan tool?		 - Go to Step 3  Go to Step 4 
3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Does the DTC fail this ignition?		 - Go to Step 4  Go to Intermittent Conditions
4 Inspect the fuse that supplies battery voltage to the MIL.
Is the fuse open?		 - Go to Step 12  Go to Step 5 
5 
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM). Refer toPowertrain Control Module (PCM) Replacement .
  3. Turn ON the ignition.
Is the MIL OFF?		 - Go to Step 6  Go to Step 13 
6 
  1. Turn OFF the ignition.
  2. Remove the fuse that supplies voltage to the MIL.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the MIL control circuit in the PCM to a good ground.
Is the voltage less than the specified value?		 0.3 V Go to Step 7  Go to Step 14 
7
  1. Turn OFF the ignition.
  2. Install the fuse that supplies voltage to the MIL.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a 3-amp fused jumper wire between the MIL control circuit of the PCM and a good ground.
Is the MIL illuminated?		 - Go to Step 11  Go to Step 8 
8
  1. Turn OFF the ignition.
  2. Remove the instrument panel cluster (IPC). Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console.
  3. Probe the MIL battery positive voltage circuit of the IPC harness connector with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 9  Go to Step 15 
9 Test the MIL control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct a condition?		 - Go to Step 18  Go to Step 10 
10 Test for an intermittent and for a poor connection at the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Repairs.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 16 
11 Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Repairs.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 17 
12 Repair the short to ground in the battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 18  -
13 Repair the short to ground in the MIL control circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 18  -
14 Repair the short to voltage in the MIL control circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 18  -
15 Repair the open in the MIL battery positive voltage. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 18  -
16 Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console.
Did you complete the replacement?		 - Go to Step 18  -
17 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 - Go to Step 18  -
18
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 19 
19 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
scientia non olet · About LEMON Manuals