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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1472 (Engine Control System - Diagnosis - 4.2L (DTC P0140 To DTC P0506)) >> Diagnosis >> DTC P0301-P0306 >> Test Description

Test Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  If the actual CKP variation values are not within the learned values, the misfire counters may increment.
DTC P0301-P0306

Step Action Values Yes No
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 
IMPORTANT: You must perform the crankshaft position (CKP) system variation learn procedure before proceeding with this diagnostic table. Refer to CKP System Variation Learn Procedure .
  1. Start the engine.
  2. Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records.
  3. Monitor all of the Misfire counters with the scan tool.
Are any of the Misfire current counters incrementing?		 - Go to Step 3  Go to Intermittent Conditions
3 Are any other DTCs set? - Go to Diagnostic Trouble Code (DTC) List Go to Step 4 
4 Can any abnormal engine noise be heard? - Go to Symptoms - Engine Mechanical in Engine Mechanical-4.2L Go to Step 5 
5
  1. Turn OFF the ignition.
  2. Remove the fuel pump relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems.
  3. Remove the ignition coil for the affected cylinder, keeping the ignition connected to the harness connector. Refer to Ignition Coil(s) Replacement .
    4. IMPORTANT: Not grounding the ignition coil may cause an erratic spark.
  4. Connect a jumper wire between the ignition coil and a good ground.
  5. Install the J 26792  Spark Tester on the ignition coil and a good ground.
  6. Crank the engine.
Does the spark tester spark?		 - Go to Step 7  Go to Step 6 
6 Inspect the affected cylinder spark plug boot for a missing or damaged ignition coil spring.
Did you find and correct the condition?		 - Go to Step 15  Go to Electronic Ignition (EI) System Diagnosis
7
  1. Remove the spark plug from the cylinder that indicated a misfire. Refer to Spark Plug Replacement .
  2. Inspect the spark plug. Refer to Spark Plug Inspection .
Does the spark plug appear to be OK?		 - Go to Step 8  Go to Step 9 
8
  1. Exchange the suspected spark plug with another cylinder that is operating properly. Refer to Spark Plug Replacement .
  2. Operate the vehicle under the same conditions that the misfire occurred.
Did the misfire move with the spark plug?		 - Go to Step 14  Go to Step 12 
9 Is the spark plug oil or coolant fouled? - Go to Symptoms - Engine Mechanical in Engine Mechanical-4.2L Go to Step 10 
10 Is the spark plug gas fouled? - Go to Step 12  Go to Step 11 
11 Did the spark plug show any signs of being cracked, worn, or improperly gapped? - Go to Step 13  Go to Step 12 
12 Perform the fuel injector coil test. Refer to Fuel Injector Coil Test .
Did you find and correct the condition?		 - Go to Step 15  Go to Symptoms - Engine Mechanical in Engine Mechanical-4.2L
13 Replace or gap the spark plug. Refer to Spark Plug Replacement .
Did you complete the action?		 - Go to Step 15  -
14 Replace the faulty spark plug. Refer to Spark Plug Replacement .
Did you complete the replacement?		 - Go to Step 15  -
15 Was the customer concern the malfunction indicator lamp (MIL) flashing? - Go to Step 16  Go to Step 17 
16
  1. Operate the vehicle at the specified value for 4 minutes.
  2. Operate the vehicle within the Conditions for Running the DTC P0420 as specified in the supporting text. Refer to DTC P0420  .
Does the DTC run and pass?		 2,500 RPM Go to Step 17  Go to DTC P0420 
17
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 18 
18 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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