Engine Controls - 'Engine Cranks But Won't Run' Updated
Bulletin No.: 04-06-04-041Date: June 14, 2004
SERVICE MANUAL UPDATE
Subject:
Revised Engine Cranks But Does Not Run Diagnostic Procedure
Models:
2001-2002 Chevrolet Camaro, Corvette
2001-2002 Pontiac Firebird
This bulletin is being issued to revise the Engine Cranks But Does Not Run diagnostic procedure in the Engine Controls sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information.
The following information has been updated within SI. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page.
Engine Cranks But Does Not Run (2001-2002 Chevrolet Camaro and Pontiac Firebird)
Description
The diagnostic table identifies a condition that causes an engine to not start. The diagnostic table directs the service technician to the appropriate system diagnosis. The diagnostic table assumes the following conditions are met:
^ The battery is completely charged. Refer to Battery Inspection/Test in Engine Electrical.
^ The engine cranking speed is within specification. Refer to Engine Cranks Slowly in Engine Electrical.
^ There is adequate fuel in the fuel tank.
Diagnostic Aids
Inspect for the following conditions:
^ The mass air flow (MAF) is compared to a calculated mass air flow based upon the manifold absolute pressure (MAP), the throttle position (TP), and the engine RPM. A skewed or unresponsive MAP sensor at key on will cause the predicted air flow value to be inaccurate. Compare the MAP and TP readings to that of a known good vehicle.
^ A faulty engine coolant temperature (ECT) sensor. Use a scan tool in order to compare the ECT with the intake air temperature (IAT) on a completely cooled engine. The ECT should be within 3°C (5°F) of the IAT.
^ For an intermittent condition, refer to Intermittent Conditions.
Test Description
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The number below refers to the step number on the diagnostic table shown.
5. This step verifies the IGN relay for proper operation. The IGN relay supplies voltage to the injectors and to the ignition coils. When the IGN relay is not operating properly, a no start condition occurs. If the test lamp does not illuminate, this indicates the IGN relay is not supplying a voltage to the fuses.
Engine Cranks But Does Not Run (2001-2002 Chevrolet Corvette)
Description
The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that causes an engine to not start. The diagnostic table directs the service technician to the appropriate system diagnosis. The diagnostic table assumes the following conditions are met:
^ The battery is completely charged. Refer to Battery Inspection/Test in Engine Electrical.
^ The engine cranking speed is within specification. Refer to Engine Cranks Slowly in Engine Electrical.
^ There is adequate fuel in the fuel tank.
Diagnostic Aids
Check for the following conditions:
^ The mass air flow (MAF) is compared to a calculated mass air flow based upon the manifold absolute pressure (MAP), the throttle position (TP), and the engine RPM. A skewed or unresponsive MAP sensor at key on will cause the predicted air flow value to be inaccurate. Compare the MAP and TP readings to that of a known good vehicle.
^ Check for a faulty engine coolant temperature (ECT) sensor. Use a scan tool in order to compare the ECT with the intake air temperature (IAT) on a completely cooled engine. The ECT should be within 3°C (5°F) of the IAT.
^ For an intermittent condition, refer to Intermittent Conditions.
Test Description
The numbers below refer to the step numbers on the diagnostic table shown.
5. This step tests the ignition relay for proper operation. The ignition relay supplies voltage to the injectors and the ignition coils. When the ignition relay is not operating properly, a no start condition occurs. If the test lamp does not illuminate, this indicates the ignition relay is not supplying a voltage to the fuses.
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