Inspection Procedure

HINT:

If DTCs besides misfire DTCs are memorized simultaneously, troubleshoot the non-misfire DTCs first.
If the misfire does not occur when the vehicle is brought to the workshop, the misfire can be confirmed by reproducing the condition of the freeze frame data. Also, after finishing the repair, confirm that there is no misfire (See confirmation driving pattern).
On 6 and 8 cylinder engines, misfiring cylinder identification is disabled at high engine speed and only a general misfire fault code P0300 is stored instead of a cylinder specific misfire fault code (P0301 to P0308).
If the misfire starts in a high engine speed area or the misfire occurs only in a high engine speed area, only code P0300 may be stored.

When only a general misfire fault code like P0300 is stored
Erase the general misfire fault code from the hand-held tester or OBD II scan tool.
Start the engine and drive the confirmation pattern (See confirmation driving pattern).
Read the value of the misfire ratio for each cylinder. Or read the DTC.
Perform repairs on the cylinder that has a high misfire ratio. Or repair the cylinder indicated by the DTC.
After finishing repairs, drive the confirmation pattern again and confirm that no misfire occurs.
When either of SHORT FT #1, LONG FT #1, SHORT FT #2 OR LONG FT #2 in the freeze frame data is over the range of +-20%, there is a possibility that the air-fuel ratio is becoming RICH (-20 % or less) or LEAN (+20 % or more).
When COOLANT TEMP in the freeze frame data is less than 80°C (176°F), there is a possibility of misfire only during engine warm-up.
If the misfire cannot be reproduced, the following reasons may apply: 1) the vehicle has low fuel, 2) improper fuel is being used, and 3) the ignition plug is contaminated.
Be sure to check the value on the misfire counter after the repair.

Are there any other codes (besides DTC P0300, P0302, P0303, P0304, P0305 or P0306) being output?
PREPARATION:
1. Connect the hand-held tester or the OBD II scan tool to the DLC3.
2. Turn the ignition switch ON and push the hand-held tester or he OBD II scan tool main switch ON.
3. When using hand-held tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
CHECK:

Read the DTC using hand-held tester or the OBD II scan tool.

RESULT:

Fig 1: Display (DTC Output) Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

If any other codes besides "P0301, P0302, P0303, P0304, P0305 or P0306" are output, perform the troubleshooting for those DTC.
1. B: Go to relevant DTC chart (See DIAGNOSTIC TROUBLE CODE CHART ).
2. A: Go to next step.
Check wire harness, connector and vacuum hose in engine room.
CHECK:
1. Check the connection conditions of wire harness and connector.
2. Check the disconnection, piping and break of vacuum hose.
1. NG: Repair or replace, then confirm that there is no misfire (See confirmation driving patter).
2. OK: Go to next step.
Check connection of PCV piping.
1. NG: Repair or replace PCV piping
2. OK: Go to next step.
Connect hand-held tester, and read the number of misfire.
PREPARATION:
1. Connect the hand-held tester or the OBD II scan to the DLC3.
2. Turn the ignition switch ON and push the hand-held or the OBD II scan tool main switch ON.
3. Start the engine.
4. When using hand-held tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / CYL#1 TO CYL#6.
CHECK:

Read the number of misfire on the hand-held tester or the OBD II scan tool.

HINT:

When a misfire is not reproduced, be sure to branch below based on the stored DTC.

RESULT:

Fig 2: High Misfire Rate Cylinder Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. B: Go to step 15 .
2. A: Go to next step.
Check spark plug and spark of misfiring cylinder.
PREPARATION:

Remove the spark plug.

CHECK:
1. Check the spark plug type (See IGNITION SYSTEM ).
2. Check the electrode for carbon deposits.
3. Check the electrode gap.
Fig 3: Checking Electrode Gap
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OK:
1. Twin ground electrodes type
  Recommended spark plug:
  
  DENSO made SK16R-P11
2. No large carbon deposit present
  Not wet with gasoline or oil.
3. Electrode gap: 1.0 to 1.2 mm (0.039 to 0.047 in.)
NOTE: If adjusting the gap of a new spark plug, bend only "the base/ground" electrode. Do not touch the tip. Never attempt to adjust the gap on a used plug.

PREPARATION:
1. Install the spark plug to the high-tension cord or ignition coil.
2. Disconnect the injector connector.
3. Ground the spark plug.
CHECK:

Check if spark occurs while the engine is being cranked.

CAUTION: Always disconnect each injector connector.

NOTE: Do not crank the engine for more than 2 seconds.

OK:

Spark jumps across electrode gap.
1. OK: Go to step 8 .
2. NG: Go to next step.
Change normal spark plug and check spark of misfiring cylinder.
PREPARATION:
1. Change to the normal spark plug.
  1. Remove the spark plug that may be faulty from the ignition coil assembly.
  2. Install the spark plug to the high-tension cord or ignition coil.
2. Disconnect the injector connector.
3. Ground the spark plug.
CHECK:

Check if spark occurs while the engine is being cranked.

CAUTION: Always disconnect each injector connector.

NOTE: Do not crank the engine for more than 2 seconds.

Fig 4: Checking Spark
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OK:

Spark jumps across electrode gap.
1. OK: Replace spark plug.
2. NG: Go to next step.
Check for open and short in harness and connector between igniter and ECM (See HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE ).
1. OK: Replace igniter, then confirm that there is no misfire.
2. NG: Repair or replace harness or connector.
Check voltage of ECM terminals for injector of failed cylinder.
PREPARATION:
1. Remove the ECM hood (See ENGINE CONTROL MODULE (ECM) ).
2. Turn the ignition switch ON.
CHECK:

Measure the voltage between applicable terminals #10 - #60 of the ECM connectors and body ground.

Fig 5: Measuring Voltage Between Applicable Terminals Of ECM Connectors & Body Ground
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OK:

Voltage: 9 to 14 V
1. OK: Go to step 11 .
2. NG: Go to next step.
Check resistance of injector of misfiring cylinder (See INJECTOR ).
1. NG: Replace injector.
2. OK: Go to next step.
Check for open and short in harness and connector between ignition switch and injector and ECM of misfiring cylinder (See HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE ).
1. NG: Repair or replace harness or connector.
2. OK: Go to next step.
Check injector of misfiring cylinder (See INSPECTION ).
1. NG: Replace injector.
2. OK: Go to next step.
Check compression pressure of misfiring cylinder (See COMPRESSION ).
1. NG: Repair or replace.
2. OK: Go to next step.
Check valve clearance of misfiring cylinder (See VALVE CLEARANCE ).
1. NG: Adjust valve clearance.
2. OK: Go to next step.
Check result of step 4 switch step by number of misfire cylinder.

Fig 6: High Misfire Rate Cylinder Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. B: Check for Intermittent problems (See PRE-CHECK ).
2. A: Go to next step.
Check valve timing (Check for looseness or a jumped tooth of timing belt) (See INSPECTION ).
1. NG: Adjust valve timing (Repair or replace timing belt).
2. OK: Go to next step.
Check fuel pressure (See FUEL PUMP ).
1. NG: Check and repair fuel pump, pressure regulator, fuel pipe line and filter (See SFI SYSTEM ).
2. OK: Go to next step.
Check mass air flow meter.
PREPARATION:
1. Connect the hand-held tester or the OBD II scan tool to the DLC3.
2. Turn the ignition switch ON.
CHECK:

Check the intake air temperature.
1. When using hand-held tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / INTAKE AIR.
2. Read its value displayed on the hand-held tester or the OBD II scan tool.
OK:

Equivalent to ambient temperature.

CHECK:

Check the air flow rate.
1. When using hand-held tester, enter the following menus: DIAGNOSIS/ENHANCED OBD II/DATA LIST/ALL/INTAKE AIR.
2. Read its value displayed on the hand-held tester or the OBD II scan tool.
OK

Fig 7: Air Flow Rate Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. NG: Repair mass air flow meter.
2. OK: Go to next step.
Check engine coolant temp. sensor (See INSPECTION ).
PREPARATION:

Remove the engine coolant temperature sensor.

CHECK:

Measure the resistance between the terminals of the engine coolant temperature sensor

Fig 8: Measuring Resistance Between Terminals Of Engine Coolant Temperature Sensor
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Resistance:

Fig 9: Tester Connection Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NOTE: In case of checking the engine coolant temperature sensor in the water, be careful not to allow water to go into the terminals. After checking, dry the sensor.

HINT:

Alternate procedure: Connect an ohmmeter to the installed engine coolant temperature sensor and read the resistance. Use an infrared thermometer to measure the engine temperature in the immediate vicinity of the sensor. Compare these values to the resistance/temperature graph. Change the engine temperature (warm up or allow to cool down) and repeat the test.
1. NG: Replace engine coolant temperature sensor
2. NG: Go to next step.
Switch step by number of misfire cylinder (Refer result of step 4 ).

Fig 10: High Misfire Rate Cylinder Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. B: Go to step 5 .
2. A: Check intermittent problems (See PRE-CHECK )