Fuel Injector Balance Test with Tech 2 (Automatic Transmission)

FUEL INJECTOR BALANCE TEST WITH TECH 2 (AUTOMATIC TRANSMISSION)

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

CIRCUIT/SYSTEM DESCRIPTION
The fuel injector balance test is performed when a misfire, knock, excessive smoke, or rough running condition exists with no electrical DTCs. This test uses the Balance Rate and Cylinder Power Balance test to identify cylinders that are not producing the designed power output. The balance rate adjustments are utilized by the engine control module (ECM) only at idle. The balance rates are the fuel adjustments for each individual cylinder based on the variations in engine crankshaft speed. The balance rates will change depending on if the transmission is in Neutral or Drive. During the Cylinder Power Balance portion of the test, the ECM turns OFF individual injectors while the engine is running. The ECM adjusts for the drop in engine RPM during cancellation and may not change on the scan tool display. The lack of power at the cancelled cylinder will feel like a misfiring cylinder or vibration. If a fuel injector is turned OFF and there is a no difference felt when compared to the other cylinders, that cylinder is identified with the concern. If the customer concern occurs during idle or during off-idle tip in acceleration, the balance rates are used to identify the cylinder with a fault related to the fuel injector or engine compression.

DIAGNOSTIC AIDS
- The Cylinder Power Balance Test may be performed at any engine speed or load from idle to wide open throttle (WOT). There is a 5-minute time limit for each test.
- A high balance rate may be caused by a fuel injector or compression only if the ECM can control fuel pressure.

CIRCUIT/SYSTEM VERIFICATION
Observe the Balancing Rate parameters with a scan tool. Normal reading should be between +4 cu.mm and -4 cu.mm in Neutral or Park and between +6 cu.mm and - 6 cu.mm in drive. With the engine running at idle the Actual Fuel Rail Pressure should be close to the Desired Fuel Rail Pressure.

CIRCUIT/SYSTEM TESTING

IMPORTANT: If any DTCs other than DTC P0300-P0308 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions

1. Start and run the engine until the engine coolant temperature (ECT) is more than 82°C (180°F).
2. Turn OFF all accessories.
3. Perform the fuel pressure regulator test, refer to Fuel Pressure Regulator Diagnosis. Fuel Pressure Regulator Diagnosis
- If the fuel pressure regulator graph was not normal, replace the fuel pressure regulator.
4. Apply the parking brake and place the transmission in Drive.
5. Hold the brake pedal in the fully applied position. A hiss will be noticeable when the brake is fully applied.
6. Idle the engine for more than 30 seconds.
7. Observe the Balancing Rate parameters with a scan tool and record the values for Cylinders 1-8.
8. Repeat steps 4-7 with the transmission in Neutral.
- Balance Rates should be between +4 cu.mm and -4 cu.mm in Neutral or Park and between +6 cu.mm and -6 cu.mm in Drive. Perform the Cylinder Power Balance Test in Special Functions if not within the specifications.
9. Record any cylinders that indicate a different cylinder power contribution and compare the Balance Rates previously recorded with the Cylinder Power Balance results.
- If the Balance Rates were not high or the Cylinder Power Balance test did not indicated a cylinder with a different power contribution, refer to Diagnostic Aids.

10. IMPORTANT: A fuel injector leak into the combustion chamber may result in mechanical damage to the cylinder. If any fuel spray comes out of a glow plug hole during the compression test, replace the fuel injector of the affected cylinder.

Perform the engine compression test. Refer to Engine Compression Test. Testing and Inspection
- If the compression test indicated any of the cylinder had low compression, refer to Cylinder Leakage Test. Component Tests and General Diagnostics

11. IMPORTANT:
- Refer to Injection System Components in Computers and Control Systems Component Views. Failure to correctly identify the cylinder positions may result in the replacement of the wrong fuel injector.
- During replacement of the injectors, inspect the inlet and outlet fittings for corrosion or contamination. Refer to Contaminants-in-Fuel Diagnosis. Contaminants-in-Fuel Diagnosis

If the engine did not have low compression on any of the cylinders, replace the fuel injectors on the cylinders that had poor cylinder power contribution, high balance rates, or a noise/smoke change during cancellation.
12. Operate the vehicle under the conditions in which the concern occurred.

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Fuel Pressure Regulator Replacement
- Fuel Injector Replacement (Left) Fuel Injector Replacement (Right) Verification Tests