P0300
The content of this article reflects the changes identified in TSB - 10-13-007.Crankshaft Position Sensor Circuit:
Injector Circuit:
Random Misfire Circuit
CIRCUIT OPERATION
- The crankshaft position sensor power is supplied from the MFI relay (terminal 1), and the ground is provided on the vehicle body.
- A 5-volt voltage is applied on the crankshaft position sensor output terminal (terminal 2) from the PCM (terminal 45). The crankshaft position sensor generates a pulse signal when the output terminal is opened and grounded.
- 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.
- he 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.
- Poor crankshaft position sensor.
- Incorrect air/fuel ratio.
- Low compression pressure.
- Skipping of timing belt teeth.
- EGR system and EGR valve failed.
- PCM failed.
DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
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. Using scan tool MB991502, check data list item 22: Crankshaft Position Sensor.
1. Check the waveform of the crankshaft position sensor while keeping the engine speed constant.
- The pulse width should be constant.
If not constant, go to Step 2.
If constant, go to Step 5.
STEP 2. Check the harness wire between the crankshaft position sensor connector A-43 and PCM connector C-90.
If the wire between the crankshaft position sensor connector A-43 and the PCM connector C-90 is not damaged, go to Step 3.
If the wire between the crankshaft position sensor connector A-43 and the PCM connector C-90 is damaged, repair it.
Then go to Step 12.
STEP 3. Check for damage of the harness connector A-43 at the crankshaft position sensor and the harness connector C-90 at the PCM.
If harness connectors A-43 and C-90 are in good condition, go to Step 4.
If harness connectors A-43 and C-90 are damaged, repair or replace them. Refer to vehicle level Testing and Inspection. Then go to Step 12.
STEP 4. Check the crankshaft position sensor and sensing plate installation state.
If incorrect, repair.
If correct, replace the crankshaft position sensor.
Then go to Step 12.
STEP 5. 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 6.
If not within specifications, replace the faulty injector. Then go to Step 12.
STEP 6. 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-90.
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 12.
If the wires between the injector connectors A-70, A-71, A-72, A-73, A-74, A-75 and the PCM connector C-90 are not damaged, go to Step 7.
If the wires between the injector connectors A-70, A-71, A-72, A-73, A-74, A-75 and the PCM connector C-90 are damaged, repair them. Then go to Step 12.
STEP 7. 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-90 at the PCM.
If harness connectors A-70, A-71, A-72, A-73, A-74, A-75 and C-90 are in good condition, go to Step 8.
If harness connectors A-70, A-71 A-72, A-73, A-74, A-75 and C-90 are damaged, repair or replace them. Refer to vehicle level Testing and Inspection. Then go to Step 12.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 8. Using scan tool MB991502, check data list item 81: Long-Term Fuel Compensation.
- The fuel trim should be between -12.5 and +12.5 when the load is 2,500 r/min (during closed loop) after the engine is warmed.
If within specifications, go to Step 9.
If not within specifications, refer to "DIAGNOSTIC TROUBLE CODE PROCEDURES".
DTC P170 - Fuel Trim Malfunction
DTC P170 - Fuel Trim Malfunction (bank 1)
DTC P173 - Fuel Trim Malfunction (bank 2)
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 9. Using scan tool MB991502, check data list item 82: Short-Term Fuel Compensation.
- The fuel trim should be between -30 and 25 when the load is 2,500 r/min (during closed loop) after the engine is warmed.
If within specifications, go to Step 10.
If not within specifications, refer to "DIAGNOSTIC TROUBLE CODE PROCEDURES".
DTC P170 - Fuel Trim Malfunction.
DTC P170 - Fuel Trim Malfunction (bank 1).
DTC P173 - Fuel Trim Malfunction (bark 2).
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 10. Using scan tool MB991502, check data list item 21: Engine Coolant Temperature Sensor.
- The engine coolant temperature and the temperature indicated on the scan tool should approximately match.
If they match, go to Step 11.
If they do not match, refer to DTC P0115 Engine Coolant Temperature Circuit Malfunction.
STEP 11. Check the following items.
1. Check the following items, and repair or replace the defective position.
a Check the ignition coil, spark plugs, spark plug cables.
b. Check compression.
c. Engine coolant temperature sensor failed.
d. Check for skipped timing belt teeth.
e. Injector clogged or seized
f. EGR valve failed.
Then go to Step 12.
STEP 12. 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.