Buick Regal: Fuel Injector 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.

Circuit/System Description

Two methods of testing fuel injector balance are available, the Active Fuel Injector Tester or a scan tool.

The Active Fuel Injector Tester and SIDI adaptor connects to the engine control module harness connectors to test the high pressure fuel pump performance, fuel injector wiring, and fuel injector operation. The Active Fuel Injector Tester displays step by step instructions to precisely determine pressure drop of each fuel injector. The scan tool fuel injector balance test is performed while the engine is running at idle. The scan tool pressurizes the fuel rail to a predetermined pressure before each fuel injector is pulsed for a precise amount of time allowing a measured amount of the fuel to be injected.

This causes a drop in the system fuel pressure that is recorded and used to compare each fuel injector.

Diagnostic Aids

• Monitoring the scan tool Cylinder 1-4 Current Misfire Counters may help to isolate the fuel injector that is causing the condition.
• Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Electrical Information Reference

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

Special Tools

• CH-47976 Active Fuel Injector Tester
• CH-47976-500 Active Fuel Injection Tester SIDI Adapter Kit
• CH-47976 - 503 Active Fuel Injection Tester cable G3
• CH-47976 - 512 Active Fuel Injection Tester cable G3b Adapter

For equivalent regional tools, refer to Special Tools (Diagnostic Tools) and Special Tools (Mechanical Tools)

Fuel Injector Coil Test

NOTE:

• The resistance test must be performed at the fuel injector or misdiagnosis will occur.
• The DMM and test leads must be calibrated to 0 Ω in order to prevent mis-diagnosis.

1. Disconnect the appropriate Q17 Fuel Injector.

2. Test for 1.3 - 1.44 Ω at 20ºC (68ºF) between the control + circuit terminal 2 and the control - circuit terminal 1 at the Q17 Fuel Injector.

• If not between 1.3 - 1.44 Ω

Replace the Q17 Fuel Injector.

• Go to next step: If between 1.3 - 1.44 Ω

3. Test for infinite resistance between each terminal at the Q17 Fuel Injector and the Q17 Fuel Injector housing/case.

• If less than infinite resistance

Replace the Q17 Fuel Injector.

• Go to next step: If infinite resistance

4. All OK. Perform the Fuel Injector Balance Test.

Fuel Injector Balance Test

NOTE:

• DO NOT perform this test if the engine coolant temperature (ECT) is above 60ºC (140ºF). Irregular fuel pressure readings may result due to hot soak fuel boiling.
• Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.

Fuel Injector Balance Test with Active Fuel Injector Tester - Preferred Method

1. Verify the battery is fully charged and all accessories are OFF.

2. Ignition OFF, all vehicle systems OFF. It may take up to 2 min for all vehicle systems to power down. Install CH-47976 and CH-47976-500. Connect CH-47976 - 503 and CH-47976 - 512 to CH-47976-500.

NOTE:

• Important that voltage is jumped to the correct fuse terminal.
• Not all (KL9) vehicle are affected. Only vehicles listed below require this jumper step.

3. For applications with Start/Stop (KL9), battery voltage must be jumped to the low/negative side of the fuse for the KR27 Starter Relay using a 3 amp fused jumper wire. Reference below to determine the appropriate fuse to remove for your application.

• Cruze (LE2) - Fuse F16UA, Fuse 16, "Fuel Injection"
• Envision (LCV / LTG) - Fuse F3UA, Fuse F03, "NON/WALK"
• Equinox/Terrain (LYX / LTG) - Fuse F3UA, Fuse 3, "Lambda 1"
• Malibu (LFV / LKN / LTG) - Fuse F76UA, Fuse 76, "PWR/TRN OFF Engine"
• Regal (LGX / LTG) - Fuse F46UA, Fuse 46, "ECM IGN"

4. Turn ON the Active Fuel Injector Tester and select the vehicle.

5. Ignition ON, perform the Injector Test with the Active Fuel Injector Tester.

• If the Active Fuel Injector Tester aborts testing due to incorrect fuel pressure or fuel leak down

Refer to Fuel System Diagnosis.

• Go to next step: If the Active Fuel Injector Tester does not abort testing

6. Compare the test results with the appropriate recommended tolerance.

• If any fuel injector exceeds the recommended tolerance

Replace the appropriate Q17 Fuel Injector(s).

• Go to next step: If all fuel injectors are within the recommended tolerance

7. All OK.

Fuel Injector Balance Test with Scan Tool

1. Verify the correct low side fuel pressure. Refer to Fuel System Diagnosis.

2. Engine idling, verify the scan tool Fuel Rail Pressure Sensor parameter is approximately 3 MPa (435 PSI).

NOTE: The engine speed must be between 600 - 1000 RPM to perform this test.

3. Select the Fuel Injector Balance function within the Control Functions menu of a scan tool.

4. Select and test an injector. Repeat for each injector.

5. Obtain and record a pressure drop value for each injector.

6. Add all of the individual pressure drop values except for the injector suspected of being faulty.

This is the total pressure drop.

NOTE: For engines with 2 banks of cylinders, only measure average pressure drop on cylinders that are on the same bank.

7.

8. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop.

9. Multiply the average pressure drop by 0.20. This is the acceptable variance from the average pressure drop, 20 percent.

10. Verify the difference between any individual pressure drop and the average pressure drop is not greater than the acceptable variance.

• If greater than the acceptable variance

Replace the Q17 Fuel Injector.

• Go to next step: If within the acceptable variance

11. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

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