Buick Regal: Fuel Injector Circuit Diagnosis

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit/System Description

The engine control module (ECM) supplies voltage to each fuel injector on the injector high voltage supply circuits. The ECM energizes each fuel injector by grounding the high voltage control circuit of the fuel injector. The ECM monitors the status of the injector high voltage supply circuits and the injector high voltage control circuits. When a fuel injector circuit condition is detected by the ECM, the affected fuel injector(s) is disabled.

Diagnostic Aids

• Performing the fuel injector coil test may help isolate an intermittent condition. Refer to Fuel Injector Diagnosis.
• If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the scan tool Injector Control Circuit Status parameters. An Injector Control Circuit Status parameter will change from OK or Not Run to Malfunction if there is a condition with the circuit or a connection.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

Powertrain Component View

Powertrain Component Views

Description and Operation

Fuel System Description

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

NOTE: Do Not perform this procedure unless directed here from the Fuel Injector Balance Test.

1. Engine idling.

2. Verify the scan tool Cylinder 1 - 4 Current Misfire Counter parameters do not increment.

• If the Cylinder 1 - 4 Current Misfire Counters increment

Refer to Circuit/System Testing.

• Go to next step: If the Cylinder 1 - 4 Current Misfire Counters do not increment

3. Verify the scan tool Cylinder 1 - 4 Injector Control Circuit Status parameters display OK.

• If the Cylinder 1 - 4 Injector Control Circuit Status parameters do not display OK

Refer to Circuit/System Testing.

• Go to next step: If the Cylinder 1 - 4 Injector Control Circuit Status parameters display OK

4. All OK.

Circuit/System Testing

1. Ignition OFF, all vehicle systems OFF, disconnect the harness connector at the K20 Engine Control Module. It may take up to 2 min for all vehicle systems to power down.

2. Test for infinite resistance between the appropriate Q17 Fuel Injector control + circuit and ground.

• If less than infinite resistance

1. Disconnect the harness connector of the Q17 Fuel Injector.
2. Test for infinite resistance between the Q17 Fuel Injector control + circuit and ground.
   • If less than infinite, repair the short to ground in the circuit.
   • Go to next step: If infinite resistance
3. Test for infinite resistance between the Q17 Fuel Injector control - circuit and ground.
   • If less than infinite, repair the short to ground in the circuit.
   • If infinite, replace the Q17 Fuel Injector.

• Go to next step: If infinite resistance

3. Ignition ON.

4. Test for less than 1 V between the Q17 Fuel Injector control + circuit and ground.

• If 1 V or greater

1. Disconnect the harness connector of the Q17 Fuel Injector, ignition ON.
2. Test for less than 1 V between the Q17 Fuel Injector control + circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, repair the short to voltage on the control - circuit.

• Go to next step: If less than 1 V

5. Ignition OFF.

6. Test for less than 3 Ω between the Q17 Fuel Injector control + circuit and control - circuit.

• If 3 Ω or greater

1. Disconnect the harness connector of the Q17 Fuel Injector.
2. Test for less than 2 Ω on the control + circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • Go to next step: If less than 2 Ω
3. Test for less than 2 Ω on the control - circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the Q17 Fuel Injector.

• Go to next step: If less than 3 Ω

7. Replace the K20 Engine Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic repair.

• Control Module References for ECM replacement, programming and setup,
• Fuel Injector Replacement

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