This bulletin outlines procedures and methods to isolate the cause(s) of mixture related driveability incidents. The bulletin also covers incidents where the check engine light is illuminated and code 45 is stored, but there are no driveability symptoms.
SERVICE PROCEDURE
NOTE: • ANY SENSOR INPUT THAT CAN CAUSE A “RICH” FUEL SIGNAL CAN CAUSE AN INJECTOR LEAK CODE. • ANY CAUSE FOR EXCESSIVE FUEL PRESSURE CAN CAUSE AN INJECTOR LEAK CODE. The best way to resolve a Code 45 or driveability incident is to carefully go through ALL the following steps: 1. CONSULT ALPHA TEST 2. MASS AIR FLOW SENSOR TEST 3. FUEL PRESSURE REGULATOR TEST 4. INJECTOR LEAK DOWN TEST 5. ENGINE COOLANT TEMPERATURE SENSOR TEST 6. OXYGEN (O2) SENSOR TEST 7. QUALITY CONTROL CHECK
1. Consult Alpha Test: The “ALPHA” reading of CONSULT indicates if the fuel mixture is rich, lean, or correct. Perform the following check to verify that a “Rich” condition exists. With CONSULT plugged in and turned on with the engine at operating temperature and just above 2000 rpm: The ALPHA reading should be between 90% to 110%, if the fuel mixture is correct. One hundred percent indicates that no correction to the base fuel schedule is necessary or the mixture control is in fail-safe. Less than 100% indicates that the O2 sensor is detecting a rich condition and less fuel will be injected to correct for this. The lower the ALPHA percentage the richer the mixture. If a reading other than 90-110% is obtained, proceed to the next step. Obtaining a base line ALPHA reading at 2,000 rpm is necessary for verifying any repairs.

Source

Related Tags: air flow sensor, alpha test, coolant, coolant temperature sensor, driveability, engine coolant temperature, engine coolant temperature sensor, excessive fuel, fuel mixture, fuel pressure regulator, leak down test, line alpha, mass air flow, mass air flow sensor, mixture control, quality control check, rpm, sensor input, test 5, test 7