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Home >> Pontiac >> 2007 >> Vibe Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - DTC P0134 To DTC P0451 >> DTC P0300 >> Test Description

Test Description

The numbers below refer to the step numbers in the diagnostic table.

  1. 1:  The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
  2. 3:  This step verifies whether the misfire is present. The scan tool will display increasing counts in the Total Misfire Current Count parameter if a misfire is occurring.
  3. 4:  This step checks whether the DTC P0300 is the result of a hard failure or an intermittent condition. Operating the vehicle in Check mode enhances the diagnostic capabilities of the PCM. For additional information on Check mode operation, refer to the Powertrain Control Module Diagnosis. The scan tool will display increasing counts in the Total Misfire Current Count parameter if a misfire is occurring.
  4. 5:  This step tests for adequate secondary ignition voltage. The fuel injectors are disabled in order to prevent unburned fuel from accumulating in the cylinders.
  5. 7:  This step inspects for a condition that can reduce the secondary ignition voltage to the spark plug. Step 6 verified that the ignition coil output is satisfactory. This step will qualify the remaining secondary ignition system components.
  6. 12:  Contaminants in the fuel, such as alcohol or water, can create a misfire condition.
  7. 13:  A vacuum leak can cause a lean misfire condition.
  8. 16:  Operating the vehicle in Check Mode enhances the diagnostic capabilities of the PCM. The catalytic converter diagnostic can be monitored on the scan tool under the I/M System Information selection. When the Catalyst test displays a YES status, indicating that the catalytic converter system diagnostic is completed, check for DTC P0420 in the Last Test Failed screen of the scan tool. If there is no DTC P0420 displayed, the catalytic converter diagnostic has run and passed, indicating that no malfunction was present this time. The DTCs MUST be cleared in order to view the Current Status of the system diagnostics being performed. Do not forget that the I/M System Information tests only indicate that the test has run, not whether the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved.
DTC P0300

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Powertrain Control Module Connector End Views  or  Engine Controls Connector End Views 
1  Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 Is DTC P0301, P0302, P0303, or P0304 also set? - Go to DTC P0301-P0304  Go to Step 3 
3 
  1. Install a scan tool.
  2. Start the engine.
  3. Monitor the Total Misfire Current Count parameter on the scan tool.
Did the scan tool indicate any misfire counts?		 - Go to Step 5  Go to Step 4 
4 
  1. Perform the scan tool Clear DTC Information function.
  2. Place the vehicle into Check mode, using the scan tool.
  3. Operate the vehicle within the Freeze Frame conditions as specified.
  4. Monitor the Total Misfire Current Count parameter on the scan tool.
Did DTC P0300 set or did the scan tool indicate any misfire counts?		 - Go to Step 5  Go to Diagnostic Aids
5 
  1. Disconnect all the fuel injector electrical connectors.
  2. Remove the ignition coil 1. Refer to Ignition Coil Replacement .
  3. Connect the ignition coil electrical connector.
  4. Connect a J 26792  Spark Tester or an equivalent to the ignition coil 1 boot. See Special Tools .
  5. Crank the engine and observe the spark tester.
  6. A crisp, blue spark should be observed.
  7. Install the ignition coil.
  8. Repeat steps 2- 5 for each of remaining the ignition coils.
Was a crisp blue spark present every engine revolution for each ignition coil?		 - Go to Step 7  Go to Step 6 
6
  1. Turn OFF the ignition.
  2. Exchange the ignition coils. Replace the suspected faulty ignition coil with a coil that produced good spark.
  3. Connect a J 26792  or an equivalent to the ignition coil boot. See Special Tools .
  4. Crank the engine while observing the spark tester.
Was a crisp, blue spark present every engine revolution?		 - Go to Step 14  Go to Electronic Ignition (EI) System Diagnosis
7 
  1. Perform a visual and physical inspection of the ignition coil boots and spark plugs for the following conditions:
    • Water intrusion
    • Corroded or poor connections to the spark plugs
    • Carbon tracking
  2. Repair the condition or replace the faulty component as necessary. Refer to Ignition Coil Replacement or Spark Plug Replacement .
Was a repair necessary?		 - Go to Step 16  Go to Step 8 
8
  1. Remove the spark plugs. Refer to Spark Plug Replacement .
  2. Visually and physically inspect the spark plugs for the correct operation and good performance. Refer to Spark Plug Inspection .
  3. Clean or replace the spark plug as necessary. Refer to Spark Plug Replacement .
Was a faulty spark plug condition found and repaired?		 - Go to Step 16  Go to Step 9 
9
  1. Turn OFF the ignition.
  2. Disconnect all 4 fuel injector electrical connectors.
  3. Install a J 34730-2B  Fuel Injector Test Lamp, or equivalent, into each fuel injector harness connector. See Special Tools .
  4. Observe the injector test lamp for each fuel injector while cranking the engine.
Does the fuel injector test lamp flash for each injector while cranking the engine?		 - Go to Step 10  Go to Fuel Injector Circuit Diagnosis
10 Perform the Fuel Injector Coil Test and the Fuel Injector Balance Test procedures. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) and Fuel Injector Balance Test with Special Tool .
Did any fuel injectors require replacement?		 - Go to Step 16  Go to Step 11 
11
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Install a fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal .
  4. Install a scan tool.
  5. Turn ON the ignition, with the engine OFF.
  6. Select Fuel Pump in the Engine Output Controls menu of the scan tool.
  7. Turn ON the fuel pump, using the scan tool.
  8. Observe the fuel pressure indicated by the fuel pressure gage with the fuel pump running.
Is the fuel pressure within the specified range?		 301-347 kPa (44-50 psi) Go to Step 12  Go to Fuel System Diagnosis
12 
  1. Check a fuel sample for the following concerns:
  2. Replace the fuel as necessary.
Was a repair necessary?		 - Go to Step 16  Go to Step 13 
13 
  1. Visually and physically inspect the following for vacuum leaks:
    • The positive crankcase ventilation (PCV) valve
    • The intake manifold gasket
    • The vacuum lines, the vacuum hoses, and the fittings
    • Inspect for incorrect vacuum hose routing.
  2. Repair as necessary.
Did you find and correct a condition?		 - Go to Step 16  Go to Step 15 
14 Replace the faulty ignition coil. Refer to Ignition Coil Replacement .
Is the action complete?		 - Go to Step 16  -
15
  1. Check for any of the following engine mechanical concerns:
    • Worn or faulty camshaft
    • Leaky or sticky valves
    • Excessive valve deposits
    • Weak valve springs
    • Incorrect valve timing
    • Intake manifold runner leaks or obstructions
    • Broken or worn piston rings
    • Leaking head gasket
  2. Repair as necessary. Refer to Diagnostic Starting Point - Engine Mechanical .
Was a basic engine mechanical concern found and repaired?		 - Go to Step 16  Go to Diagnostic Aids
16
  1. In order to ensure that the performance of the catalyst has not been affected by the fault that set this DTC, place the vehicle in Check Mode. Refer to Service Bay Test .
  2. While in Check Mode, operate the vehicle within the conditions for running and setting DTC P0420 and verify that DTC P0420 runs and passes. Refer to DTC P0420 .
Does DTC P0420 run and pass?		 - Go to Step 17  Go to DTC P0420 
17
  1. Perform the scan tool Clear DTC Information function.
  2. Operate the vehicle within the Freeze Frame conditions that set the DTC.
  3. Monitor the Total Misfire Current Count parameter on the scan tool.
Did a DTC set or did the scan tool indicate any misfire counts?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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