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DTC P0300: Engine Misfire Detected: Troubleshooting

TROUBLESHOOTING CHART

Step Action Value(s) Yes No
1 Perform an On-Board Diagnostic (OBD II) System Check.
Was the check performed?		 - Go to Step 2 Go to On-Board Diagnostic (OBD II) System Check
2
  1. Install a scan tool to the Data Link Connector (DLC).
  2. Turn the ignition ON, with the engine OFF.
  3. Request Diagnostic Trouble Codes (DTCs).

Are the DTCs regarding injectors set?		 - Go to applicable DTC table Go to Step 3
3
  1. Perform a visual/physical inspection.
  2. Make any repairs that are necessary.

Is the repair complete?		 - Go to Step 27 Go to Step 4
4 Start the engine and allow it to idle.
Are any Misfire Current counters incrementing?		 - Go to Step 5 Go to Step 6
5 Are all counters equal (within a percentage of each other)? - Go to Step 7 Go to Step 11
6
  1. Turn the ignition ON, with the engine OFF.
  2. Review the Freeze Frame data, and note the parameters.
  3. Operate the vehicle within the Freeze Frame conditions and conditions for setting this DTC as noted.

Are any Misfire Current counters incrementing?		 - Go to Step 5 Go to Diagnostic Aids
7
  1. Turn the engine OFF.
  2. Install a fuel pressure gauge to the fuel rail.
  3. Observe the fuel pressure with the engine running.

Is the fuel pressure within the specified value?		 379 - 393 kPa (55 - 57 psi) Go to Step 8 Go to "Fuel System Diagnosis"
8 Check the fuel for contamination.
Is the fuel OK?		 - Go to Step 9 Go to Step 10
9 Check for a basic engine problem and repair as necessary.
Is the repair complete?		 - Go to Step 27 -
10 Replace the contaminated fuel.
Is the repair complete?		 - Go to Step 27 -
11
  1. Turn the engine OFF.
  2. Disconnect the fuel injector harness connector.
  3. Install a spark tester on cylinder #1 spark plug cable.
  4. Crank the engine and check for spark.
  5. Repeat the above procedure on cylinders #2, #3 and #4.

Is a spark observed on all four spark plug cables?		 - Go to Step 12 Go to Step 20
12 Replace any malfunctioning spark plugs if necessary.
Is the repair complete?		 - Go to Step 27 Go to Step 13
13
  1. Turn the engine OFF.
  2. Disconnect the fuel injector connectors from the injectors.
  3. Install an injector test light on the injector harness connector for the cylinders that had misfired.
  4. Crank the engine and note the test light.

Does the injector test light blink?		 - Go to Step 14 Go to Step 15
14 Perform the FUEL INJECTOR BALANCE TEST .
Are the fuel injectors OK?		 - Go to Step 9 Go to Step 16
15
  1. Disconnect the injector test light.
  2. With a test light connected to ground, probe the ignition feed terminal 2 of the injector harness connector for each cylinder that had misfire.
  3. Crank the engine.

Does the test light illuminate?		 - Go to Step 17 Go to Step 19
16 Replace any malfunctioning fuel injectors.
Is the repair complete?		 - Go to Step 27 -
17 Check the affected fuel injector driver circuit at terminals E63, E56, E55 and E64 for an open or short to voltage.
Is a problem found?		 - Go to Step 18 Go to Step 24
18 Repair the open or the shorted fuel injector driver circuit.
Is the repair complete?		 - Go to Step 26 -
19 Repair the open ignition feed circuit between the fuel injector harness connector and the fuel injector connector.
Is the repair complete?		 - Go to Step 27 -
20 Measure the resistance of the spark plug cable that the spark plug tester did not spark.
Is the resistance of the spark plug cable less than the specified value?		 30, 000 Ω Go to Step 21 Go to Step 25
21 Inspect the Engine Control Module (ECM) connector and connections.
Are the connections OK?		 - Go to Step 22 Go to Step 23
22 Check the affected cylinders ignition control circuit for an open or short and repair as necessary.
Is the repair complete?		 - Go to Step 27 Go to Step 26
23 Repair the connector or connections.
Is the repair complete?		 - Go to Step 27 -
24
  1. Turn the ignition OFF.
  2. Replace the ECM.

Is the repair complete?		 - Go to Step 27 -
25 Replace the spark plug cable.
Is the repair complete?		 - Go to Step 27 -
26 Replace the faulty ignition coil.
Is the repair complete?		 - Go to Step 27 Go to Step 24
27
  1. Using the scan tool, clear the DTCs.
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the conditions for setting this DTC as supported in the text.

Does the scan tool indicate that this diagnostic ran and passed?		 - Go to Step 28 Go to Step 2
28 Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?		 - Go to applicable DTC table System OK
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