P0304
The content of this article reflects the changes identified in TSB - 10-13-007.Misfire Detected Circuit
- Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.
CIRCUIT OPERATION
- Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The ECM
DTC SET CONDITIONS
Check Conditions
- Engine speed is between 500 and 6,000 r/min.
- Engine coolant temperature is higher than -10 °C (14 °F).
- Intake air temperature is higher than -10 °C (14 °F).
- Barometric pressure is at between 76 kPa (11 psi) and 106 kPa (15 psi).
- Adaptive learning is complete for the vane which generates a crankshaft position signal.
- While the engine is running, excluding gear shifting, deceleration, sudden acceleration/deceleration and A/C compressor switching.
- The throttle deviation is -0.059 volt/10 ms to +0.059 volt/10 ms.
Judgement Criteria (change in the angular acceleration of the crankshaft is used for misfire detection).
- Misfire has occurred more frequently than allowed during the last 200 revolutions [when the catalyst temperature is higher than 950 °C (1,742 °F)].
or
- Misfire has occurred in 20 or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard).
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Fuel aeration due to low fuel level.
- Ignition system related part(s) failed.
- Low compression pressure.
- Injector failed.
- ECM failed.
- PCM failed.
DIAGNOSIS
Check whether fuel may be aerated due to low fuel level.
^ Check whether users have experienced the lack of fuel or not.
Q: Has the user ever experienced the lack of fuel?
YES: Ensure fuel level is not low, erase the DTC, and re-evaluate for misfire condition using the appropiate OBD-II Drive Cycle Procedure.
NO: Go to Step 1.
STEP 1. Check the spark plugs.
1. Check that the plug is not burned, that the insulator plug is not damaged, and that the seizure state is good.
2. If cleaning is required due to carbon deposits, etc., clean using a plug cleaner or wire brush, etc.
3. Check the plug gap using a plug gap gauge, and adjust if not within the standard value.
Standard value: 1.0 - 1.1 mm (0.039 - 0.043 inch)
Q: Is the spark plug in good condition?
YES: Go to Step 2.
NO: Replace the spark plug. Then go to Step 9.
STEP 2. Check the spark plug cable.
1. Check the cap and coating for cracks.
2. Measure the resistance.
Limit: maximum 19 kohm
Q: Is the resistance normal?
YES: Go to Step 3.
NO: Replace the spark plug cable. Then go to Step 9.
STEP 3. Check the injector.
1. Disconnect the injector connector B-22
2. Measure the resistance between injector side connector terminal 1 and 2.
Standard value: 13 - 16 ohm [at 20 °C (68 °F)]
Q: Is the resistance standard value?
YES: Go to Step 4.
NO: Replace the injector. Then go to Step 9.
STEP 4. Check connector at injector for damage.
a. Check the connector B-22 when checking No.1 cylinder
b. Check the connector B-20 when checking No.2 cylinder.
c. Check the connector B-18 when checking No.3 cylinder.
d. Check the connector B-17 when checking No.4 cylinder.
Q: Is the connector in good condition?
YES: Go to Step 5.
NO: Repair or replace the injector. Refer to Harness Connector Inspection. Then go to Step 9.
STEP 5. Check connector C-121 at ECM
Q: Is the connector in good condition?
YES: Go to Step 6.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 9.
STEP 6. Check for harness damage between injector connector and ECM connector
a. Check the harness wire between injector connector B-22 terminal 2 and ECM connector C-121 terminal 1
b. Check the harness wire between injector connector B-20 terminal 2 and ECM connector C-121 terminal 14
c. Check the harness wire between injector connector B-18 terminal 2 and ECM connector C-121 terminal 2
d. Check the harness wire between injector connector B-17 terminal 2 and ECM connector C-121 terminal 15
Q: Is the harness wire in good condition?
YES: Go to Step 7.
NO: Repair it. Then go to Step 9.
STEP 7. Check the compression.
Refer to On-Vehicle Service - Compression Pressure Check.
Q: Are there any abnormalities?
YES: Go to Step 5.
NO: Repair or replace it. Then go to Step 9.
STEP 8. Replace the injector.
1. Replace the injector.
2. Carry out a test drive with the drive cycle pattern. Refer to, Procedure 6 - Other Monitor.
3. Check the diagnostic trouble code (DTC).
Q: Is the DTC P0301, P0302, P0303, P0304 output?
YES: Replace the ECM or PCM. Then go to Step 9.
NO: The inspection is complete.
STEP 9. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to, Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is the DTC P0301, P0302, P0303, P0304 output?
YES: Retry the troubleshooting.
NO: The inspection is complete.