GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Optra - Mexico 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 Engine Cranks But Does Not Run

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 provide an overview of each diagnostic category.

Circuit/System Description

This Engine Cranks but Does Not Run diagnostic is an organized approach to identify a condition which causes the engine to crank but not start. This diagnostic directs the technician to the appropriate system diagnosis.

Diagnostic Aids

Inspect for any of the following conditions:

    • Insufficient fuel can cause a no start condition. Thoroughly inspect the fuel delivery system for sufficient fuel volume to the fuel injectors. Inspect the fuel supply components for partial blockage or restrictions.
    • Fuel injectors with partially blocked and restricted nozzles, or a malfunctioning solenoid, can cause a no start condition. Refer to Fuel Injector Solenoid Coil Test and Fuel Injector Balance Test with Special Tool .
    • There may be fuel spray at the fuel injectors and the indicated fuel pressure may be correct, yet there may not be enough fuel to start the engine. If the fuel injectors and the injector circuit are OK, and fuel spray is detected, the fuel injector ON time may be inadequate. If the engine control module (ECM) receives incorrect inputs from the various information sensors, the fuel delivered by the fuel injectors may be inadequate to start the engine. Check all the engine data parameters with a scan tool and compare the values indicated with the expected values or the values from a known good vehicle.
    • Check the crankshaft position (CKP) sensor engine reference signal with a scan tool. Observe the Engine Speed parameter while cranking the engine. The scan tool should indicate a steady 200-300 RPM while cranking. If erratic values, such as sudden spikes in the engine speed are displayed, the engine reference signal is not stable enough for the engine to start and run properly.
    • Inspect the engine for good secure electrical grounds.
    • If the engine almost starts and then stalls, check for an open in the ground circuits of the CKP sensor and the camshaft position (CMP) sensor.
    • Water or foreign material in the fuel can cause a no start or engine will not stay running condition. During freezing weather water can freeze inside the fuel system. The engine may start after 30 minutes in a heated repair shop. The malfunction may not recur until parked overnight in freezing temperatures. Extreme weather conditions can cause contaminated fuel to prevent the vehicle from starting.
    • A vehicle that starts and runs after being brought to the repair shop for a no start condition, may have an ignition system that is susceptible to moisture. Spray water on the ignition system components and the wiring in order to check for an engine starting or will not stay running concern.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Connector End Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Special Tools Required

    •  J 34730-1A Fuel Pressure Gage
    •  J 26792 Spark Tester

Circuit/System Verification

Important: This diagnostic assumes the following:

   • The battery is completely charged. Refer to Battery Inspection/Test .
   •  System voltage levels are adequate for starter motor operation.
   • The engine cranking speed is acceptable. Refer to Engine Cranks Slowly .
   • There is adequate fuel in the fuel tank.

  1. Crank the engine for 15 seconds. Observe the DTC information with a scan tool. The following DTCs should not be set:

    2. P0117, P0118, P0122, P0123, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0335, P0336, P0351, P0352, P0562, P0563, P0601, P0602, P0603, P0604, P0606, P0685, P1626, P2105, P2610 or U0101.

    ⇒If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Ignition ON, observe the Theft Deterrent parameter with a scan tool. The parameter should display Disabled.
    3. ⇒If Enabled is displayed, refer to Symptoms - Theft Deterrent .
  3. Observe the scan tool Engine Speed parameter while cranking the engine. The parameter should indicate an engine speed greater than 0 RPM.
    4. ⇒If the engine speed is 0 RPM, refer to DTC P0335, P0336, or P0337 for further diagnosis.
  4. Cycle the ignition from OFF to ON. You should hear and feel an audible click from the EC ignition relay. Repeat as necessary in order to verify EC ignition relay operation.
    5. ⇒If the EC ignition relay does not click, refer to DTC P0685 for further diagnosis.
  5. Ignition OFF, disconnect the fuel pump relay.
  6. Connect a J 26792 to the boot of a spark plug wire of a cylinder and a good ground.

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

  7. While cranking the engine, verify that the spark tester sparks.
    8. ⇒If there is no spark, refer to Electronic Ignition (EI) System Diagnosis .
  8. Ignition OFF, install the fuel pump relay.
  9. Ignition ON, command the fuel pump ON with a scan tool. You should hear the fuel pump turn ON.
    10. ⇒If the fuel pump does not turn ON, refer to Fuel Pump Electrical Circuit Diagnosis .
  10. Ignition OFF, disconnect the harness connector of a fuel injector.
  11. Connect a J 34730-405 between the control circuit and the ignition 1 voltage circuit. While cranking the engine, the injector test lamp should flash.
    12. ⇒If the injector test lamp does not flash, refer to DTC P0201, P0202, P0203, or P0204 or DTC P0261, P0262, P0264, P0265, P0267, P0268, P0270, or P0271 .
  12. Ignition OFF, install the J 34730-1A . Refer to Fuel Pressure Gage Installation and Removal .

    13. Important: 

       • The fuel pump may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure.
       • Do NOT start the engine for this test.

  13. Ignition ON, command the fuel pump ON with a scan tool. The fuel pressure should be between 380-427 kPa (55-62 psi).
    14. ⇒If the fuel pressure is not within the specified range, refer to Fuel System Diagnosis .
  14. Verify that the following conditions do not exist:
    15. • Collapsed air intake duct to the throttle body
    • Restricted air filter element
    • Spark plugs for being gas or coolant fouled--Refer to Spark Plug Inspection
    • A skewed manifold absolute pressure (MAP) sensor--Refer to DTC P0106
    • A skewed engine coolant temperature (ECT) sensor--Refer to DTC P0125 or P0128
    • Exhaust system restricted--Refer to Restricted Exhaust
    • Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis
    • Engine mechanical condition, for example, worn timing belt or low compression. Refer to Symptoms - Engine Mechanical or Engine Compression Test
         ⇒If you find any of the above conditions, repair as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.