This Engine Cranks but Does Not Run diagnostic is an organized approach to identify a condition which causes the engine to crank but does not continue to run. This diagnostic directs the service technician to the appropriate system diagnosis. This diagnostic assumes the vehicle system voltage levels are adequate for starter motor operation. Refer to Battery Inspection/Test and Engine Cranks Slowly. The fuel level supply must be adequate, and the fuel quality must be able to sustain the combustion process.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

Attempt to start the engine. The engine should start and run.

1. Crank the engine for up to 30 seconds.
2. Observe the vehicle DTC information with a scan tool.

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If any of the following DTCs are set, diagnose these first: DTC P0117, P0118, P0122, P0123, P0201-P0208, P0222, P0223, P0335, P0336, P0351-P0358, P0513, P0562, P0563, P0601-P0604, P0606, P0607, P062F, P0633, P0685, P0690, P1516, P1631, P1682, or P2610. Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

3. With the ignition ON and the engine OFF, test the fuses that are supplied ignition 1 voltage by the powertrain relay. The test lamp should illuminate ON for each test point of the fuses.

⇒	If the test lamp does not illuminate on, for at least one test point of each fuse, refer to DTC P0685, P0689, or P0690.

4. Crank the engine for 15 seconds. Observe the engine speed parameter with a scan tool.

⇒	If engine RPM is not indicated, refer to DTC P0335 or DTC P0336.

5. Install a spark plug tester onto one ignition module/coil assembly, on each bank of the engine.
6. Observe both spark plug testers.

Note: An erratic or weak spark is considered a no spark condition.

7. Crank the engine for 15 seconds. The ignition coil secondary voltage should be observed across the gap of both spark plug testers.

⇒	If the ignition coil secondary voltage is not observed, is inconsistent, or weak on either spark plug tester, refer to Electronic Ignition (EI) System Diagnosis.

8. With the ignition ON and the engine OFF, command the fuel pump ON and OFF with the scan tool. The fuel pump should energize when commanded ON, and de-energize when commanded OFF.

⇒	If the fuel pump does not turn ON and OFF, refer to Fuel System Diagnosis.

9. Turn OFF the ignition.
10. Install the J 34730-1A Fuel Pressure Gage. With the ignition ON and the engine OFF, command the fuel pump ON several times with the scan tool. Refer to Fuel System Diagnosis for the fuel pressure specification.
11. Inspect for the following conditions:

•	Compare the actual engine coolant temperature to the ECT parameter

•	Filter and air intake system for restrictions and obstructions

•	Test the fuel for contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis.

•	Inspect the spark plugs--Refer to Spark Plug Inspection.

•	Test the exhaust system for restrictions--Refer to Restricted Exhaust.

•	Engine mechanical conditions, such as worn timing chain, sprocket gears, low compression, etc--Refer to Symptoms - Engine Mechanical.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.