P0303
The content of this article reflects the changes identified in TSB - 10-13-007.Injector Circuit:
Misfire Detected Circuit
CIRCUIT OPERATION
- The injector power is supplied from the MFI relay (terminal 1).
- The PCM controls the injector by turning the power transistor in the PCM "ON" and "OFF".
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The PCM checks for such changes in engine speed.
DTC SET CONDITIONS
Check Area
- Five seconds or more have passed after the engine was started.
- Engine speed is between 440 and 6,000
- Engine coolant temperature is higher than -10° C (14° F).
- Intake air temperature is higher than -10° C (14° F).
- Barometric pressure is higher than 76 kPa (11 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.
Judgement Criteria (change in the angular acceleration of the crankshaft is used for misfire detection).
- Misfire has occurred in 4 or more of the last 200 revolutions [when the catalyst temperature is higher than 950° C (1742° 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.
- PCM failed.
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 injectors.
1. Disconnect each injector connector.
2. Measure the resistance between injector side connector terminals 1 and 2.
Standard value: 13 - 16 ohms [at 20° C (68° F)]
If within specifications, go to Step 2.
If not within specifications, replace the faulty injector. Then go to Step 5.
STEP 2. Check the harness wire between the injector connectors A-70, A-71, A-72, A-73, A-74, A-75 and the PCM connector C-89.
NOTE: After inspecting the intermediate connector A-04, inspect the wire. If the intermediate connector A-04 is damaged, repair or replace it. Refer to vehicle level Testing and Inspection. Then go to Step 5.
If the wires between the injector connectors A-70, A-71, A-72, A-73, A-74, A-75 and the PCM connector C-89 are not damaged, go to Step 3.
If the wires between the injector connectors A-70, A-71, A-72, A-73, A-74, A-75 and the PCM connector C-89 are damaged, repair them. Then go to Step 5.
STEP 3. Check for damage of the harness connectors A-70, A-71, A-72, A-73, A-74, A-75 at the injector and the harness connector C-89 at the PCM.
If harness connectors A-70, A-71, A-72, A-73, A-74, A-75 and C-89 are in good condition, go to Step 4.
If harness connectors A-70, A-71, A-72, A-73, A-74, A-75 and C-89 are damaged, repair or replace them. Refer to vehicle level Testing and Inspection. Then go to Step 5.
STEP 4. Check the following items.
1. Check the following items, and repair or replace.
a. Check the spark plugs, spark plug cables.
b. Check compression.
Then go to Step 5.
STEP 5. Test the OBD-II drive cycle
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
2. Read the diagnostic trouble code, and confirm that a diagnostic trouble code is not being output.