Refer to
Cell 21: Ignition System
and to
Cell 21: CMP Sensor and CKP Sensor
.
Circuit Description
The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring changes in the crankshaft rotation for each cylinder the PCM counts individual misfire events. The malfunction indicator lamp (MIL) illuminates when the misfire rate equals or exceeds a pre-determined count. A misfire rate that is high enough can cause the catalytic converter to overheat under certain driving conditions. The MIL will flash On and Off when the conditions for catalytic converter overheating are present.
Conditions for Running the DTC
| • | The engine coolant temperature is between -10°C and +110°C (14°-230°F). |
| • | The intake air temperature is between -10°C and +70°C (14°-158°F). |
| • | The barometric pressure is more than 75 kPa. |
| • | The TP sensor change is less than 1.9 degrees in 16 firing events. |
| • | The change in the manifold absolute pressure (MAP) is less than 1.3 kPa in 60 firing events. |
| • | The engine speed is less than 6,500 RPM, and the change in engine speed is less than 200 per 50 msec. |
Conditions for Setting the DTC
| • | The misfire rate at 200 engine revolutions is more than a specified value. |
| • | The misfire rate at 1,000 engine revolutions is more than a specified value. |
| • | The conditions are present from 5 seconds after the engine is started to 1 second before fuel shut-off. |
Action Taken When the DTC Sets
| • | The PCM flashes the malfunction indicator lamp (MIL) the first time a catalyst damaging misfire occurs. |
| • | The PCM illuminates the MIL the second time emission thresholds are exceeded and the diagnostic fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutive trips during which the diagnostic runs and no fault is detected. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the scan tool Clear DTC Information function or disconnect the PCM battery feed in order to clear the DTC. |
Diagnostic Aids
Check for any of the following conditions:
| • | If any DTCs other than misfire DTCs (P0300- P0304) are present, diagnose those DTCs first. |
| • | Check for the engine overheating. |
| • | Check for engine vacuum leaks. |
| • | Check for a PCV system malfunction. Perform a functional check of the PCV valve. Refer to Crankcase Ventilation System Inspection . |
| • | Look for an intermittent ignition system malfunction caused by the spark plugs,the ignition wires, or the ignition coil. Check the ignition system performance with an engine oscilloscope. |
| • | Fuel pressure that is out of specification--Refer to Fuel System Diagnosis . |
| • | A fuel injector malfunction may cause a DTC P0302 to set. Check the performance of the fuel injectors. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) and Sequential Multiport Fuel Injector Balance Test . |
| • | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
| • | An engine mechanical malfunction--Measure the engine cylinder compression and the valve lash adjustment for comparison to the manufacturer's specifications. Refer to Engine Compression Test in Engine Mechanical. |
| • | A damaged wiring harness--Inspect the applicable wiring harness for damage and repair as necessary. |
| • | A misfire DTC can also be the result of a defective signal rotor on the crankshaft timing belt pulley. Remove the crankshaft position (CKP) sensor and inspect the crankshaft signal rotor through the sensor hole. Check the crankshaft signal rotor for foreign material or damaged teeth. |
An intermittent fault may be duplicated by wetting the secondary ignition system with water and operating the vehicle under the conditions that set the DTC.
If a DTC P0302 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.
-
This step determines if a fault is present.
-
The #2 ignition coil provides the spark for cylinders 2 and 3 simultaneously. Any condition that effects the ignition circuit of cylinder 3 may also have an effect on the ignition circuit of cylinder 2.Inspect both sides of the ignition coil for cracks, for carbon tracking, and for corrosion.
-
The ignition coil may have an internal fault.
-
This step checks for the electrical signal from the PCM for the operation of the fuel injector. If the injector test lamp does not illuminate, the fuel injector control circuit is diagnosed for a faulty condition.
-
A faulty fuel injector can cause a misfire condition and a DTC P0302 to set.
-
This step checks for a mechanical fault as the cause of the misfire condition. Low engine compression and an incorrect valve lash may also cause a rough idling condition.
-
This step checks for a faulty crankshaft signal rotor. Visually inspect the teeth of the signal rotor through the CKP sensor aperture for damage, for foreign material, and for misalignment.
Step | Action | Value(s) | Yes | No | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On--Board Diagnostic (OBD) System Check? | -- | |||||||||||||||||||||
2 | Start the engine. Is a misfire present at Idle? | -- | ||||||||||||||||||||
Is DTC P0302 set? | -- | Go to Diagnostic Aids | ||||||||||||||||||||
4 |
Was a repair necessary? | -- | ||||||||||||||||||||
5 |
Is a blue spark present? | -- | ||||||||||||||||||||
6 |
Was a repair necessary? | -- | ||||||||||||||||||||
7 |
Did you replace the spark plug boot? | 100 ohms | ||||||||||||||||||||
Was a repair necessary? | -- | |||||||||||||||||||||
Replace the #2 ignition coil. Refer to Ignition Coil Replacement . Is the action complete? | -- | -- | ||||||||||||||||||||
10 |
Did you replace the #2 spark plug? | -- | ||||||||||||||||||||
Did the injector test lamp flash while cranking the engine? | -- | |||||||||||||||||||||
Check the #2 fuel injector for correct operation. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) and to Sequential Multiport Fuel Injector Balance Test . Was a faulty fuel injector found and replaced? | -- | |||||||||||||||||||||
13 | Was the spark plug replaced because of fuel, oil, or coolant fouling? | -- | ||||||||||||||||||||
Was a basic engine mechanical concern found and repaired? | -- | |||||||||||||||||||||
15 |
Was a repair necessary? | -- | ||||||||||||||||||||
Was a repair necessary? | -- | Go to Diagnostic Aids | ||||||||||||||||||||
17 |
Does the scan tool display any DTCs? | -- | Go to the applicable DTC table | System OK |
