DTC Troubleshooting: P0301 (71-1), P0302 (72-1), P0303 (73-1), P0304 (74-1)

DTC P0301 (71-1):  No. 1 Cylinder Misfire
  
  
DTC P0303 (73-1):  No. 3 Cylinder Misfire
  
  

1.After checking and recording the freeze data, reset the ECM/PCM. If there is no freeze data of the misfire, just clear the DTC.

2.Start the engine, and listen for a clicking sound at the injector at the problem cylinder.

Does it click?


YES - Go to 3.


NO - Go to 32.


3.Turn the ignition switch OFF, and reset the ECM/PCM.

4.Exchange the ignition coil from the problem cylinder with one from another cylinder.

5.Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.

6.Check the DTC or the Temporary DTC with the scan tool.

Is DTC or Temporary DTC P0301, P0302, P0303 or P0304 indicated?


YES - Go to 7.


NO - Intermittent misfire due to poor contact at the ignition coil connector (no misfire at this time).n

7.Determine which cylinder(s) had the misfire.

Does the misfire occur in the other cylinder whose ignition coil was exchanged?


YES - Replace the faulty ignition coil.n


NO - Go to 8.


8.Turn the ignition switch OFF, and reset the ECM/PCM.

9.Exchange the spark plug from the problem cylinder with one from another cylinder.

10.Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.

11.Check the DTC or the Temporary DTC with the scan Tool.

Is DTC or Temporary DTC P0301, P0302, P0303 or P0304 indicated?


YES - Go to 12.


NO - Intermittent misfire due to spark plug fouling, etc. (no misfire at this time).n


12.Determine which cylinder(s) had the misfire.

Does the misfire occur in the other cylinder whose spark plug was exchanged?


YES - Replace the faulty spark plug.n


NO - Go to 13.


13.Turn the ignition switch OFF, and reset the ECM/PCM.

14.Exchange the injector from the problem cylinder with one from the another cylinder.

15.Let the engine idle for 2 minutes.

16.Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.

17.Check for a DTC or Temporary DTC with the scan Tool.

Is DTC or Temporary DTC P0301, P0302, P0303 or P0304 indicated?


YES - Go to 18.


NO - Intermittent misfire due to bad contact at the injector connector (no misfire at this time).n


18.Determine which cylinder(s) had the misfire.

Does the misfire occur in the other cylinder whose injector was exchanged?


YES - Replace the faulty injector.n


NO - Go to 19.


19.Turn the ignition switch OFF.

20.Disconnect the ignition coil 3P connector from the problem cylinder.

21.Turn the ignition switch ON (II).

22.Measure voltage between ignition coil 3P connector terminal No. 3 and body ground.

 

Is there battery voltage?


YES - Go to 23.


NO - Repair open or short in the wire between the No. 1 IGN COIL (15A) fuse and the ignition coil.n


23.Turn the ignition switch OFF.

24.Check for continuity between ignition coil 3P connector terminal No. 2 and body ground.

 

Is there continuity?


YES - Go to 25.


NO - Repair open in the wire between the ignition coil and  G101.n


25.Disconnect the negative cable from the battery.

26.Disconnect ECM/PCM connector A (31P).

27.Check for continuity between body ground and the appropriate ECM/PCM connector terminal (see table).

 

PROBLEM CYLINDER DTC ECM/PCM TERMINAL WIRE COLOR 
No. 1 P0301 A30 YEL/GRN 
No. 2 P0302 A29 BLU/RED 
No. 3 P0303 A28 WHT/BLU 
No. 4 P0304 A27 BRN 

Is there continuity?


YES - Repair short in the wire between the  ECM/ PCM and the ignition coil.n


NO - Go to 28.


28.Connect the appropriate ignition coil 3P connector terminal No. 1 and body ground with a jumper wire (see table).

 

PROBLEM CYLINDER DTC WIRE COLOR 
No. 1 P0301 YEL/GRN 
No. 2 P0302 BLU/RED 
No. 3 P0303 WHT/BLU 
No. 4 P0304 BRN 

29.Check for continuity between body ground and the appropriate ECM/PCM connector terminal (see table).

 

PROBLEM CYLINDER DTC ECM/PCM TERMINAL WIRE COLOR 
No. 1 P0301 A30 YEL/GRN 
No. 2 P0302 A29 BLU/RED 
No. 3 P0303 A28 WHT/BLU 
No. 4 P0304 A27 BRN 

Is there continuity?


YES - Go to 30.


NO - Repair open in the wire between the  ECM/ PCM and the ignition coil.n


30.Reconnect the negative cable to the battery.

31.Check the compression.

Is the engine compression OK?


YES - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original  ECM/ PCM.n


NO - Repair the engine.n


32.Disconnect the negative cable from the battery.

33.Disconnect ECM/PCM connector B (24P).

34.Reconnect the negative cable to the battery.

35.Turn the ignition switch ON (II).

36.Measure voltage between body ground and the appropriate ECM/PCM connector terminal (see table).

 

PROBLEM CYLINDER DTC ECM/PCM TERMINAL WIRE COLOR 
No. 1 P0301 B5 BRN 
No. 2 P0302 B4 RED 
No. 3 P0303 B3 BLU 
No. 4 P0304 B2 YEL 

Is there battery voltage?


YES - Go to 37.


NO - Go to 45.


37.Turn the ignition switch OFF, and remove the engine cover.

38.Disconnect the injector 2P connector on the problem cylinder.

39.Measure the resistance between injector 2P connector terminals No. 1 and No. 2.

 

Is there 10 W-13W?


YES - Go to 40.


NO - Replace the injector.n

40.Exchange the injector from the problem cylinder with one from another cylinder.

41.Let the engine idle for 2 minutes.

42.Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.

43.Check for a DTC or Temporary DTC with a scan tool.

Is DTC or Temporary DTC P0301, P0302, P0303, or P0304 indicated?


YES - Go to 44.


NO - Intermittent misfire due to injector malfunction etc.n


44.Determine which cylinder(s) had the misfire.

Does the misfire occur in the other cylinder whose injector was exchanged?


YES - Replace the faulty injector.n


NO - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original  ECM/ PCM.n


45.Turn the ignition switch OFF and remove the engine cover.

46.Disconnect the injector 2P connector on the problem cylinder.

47.Turn the ignition switch ON (II).

48.Measure voltage between injector 2P connector terminal No. 1 and body ground.

 

Is there battery voltage?


YES - Go to 49.


NO - Repair open in the wire between the injector and the  PGM-FI main relay.n


49.Turn the ignition switch OFF.

50.Check for continuity between body ground and the appropriate ECM/PCM connector terminal (see table).

 

PROBLEM CYLINDER DTC ECM/PCM TERMINAL WIRE COLOR 
No. 1 P0301 B5 BRN 
No. 2 P0302 B4 RED 
No. 3 P0303 B3 BLU 
No. 4 P0304 B2 YEL 

Is there continuity?


YES - Repair short in the wire between the  ECM/ PCM and the injector.n


NO - Go to 51.

51.Connect the appropriate injector 2P connector terminal No. 2 to body ground with a jumper wire (see table).

 

PROBLEM CYLINDER DTC WIRE COLOR 
No. 1 P0301 BRN 
No. 2 P0302 RED 
No. 3 P0303 BLU 
No. 4 P0304 YEL 

52.Check for continuity between body ground and the appropriate ECM/PCM connector terminal (see table).

 

PROBLEM CYLINDER DTC ECM/PCM TERMINAL WIRE COLOR 
No. 1 P0301 B5 BRN 
No. 2 P0302 B4 RED 
No. 3 P0303 B3 BLU 
No. 4 P0304 B2 YEL 

Is there continuity?


YES - Replace the injector, then recheck.n


NO - Repair open in the wire between the  ECM/ PCM and the injector.n