P0305

DTC P0304 Cylinder Misfire Detected

Circuit Description
Misfire is monitored as a function of the combustion quality (CQ) signals generated from the ignition current sense system. Combustion signals represent the degree of combustion in each cylinder. Misfire is detected when the combustion signal is below a predetermined value.

This DTC P0304 will determine if the No.4 cylinder misfire is occurring by monitoring the Combustion Quality.

Conditions for Setting the DTC
- None of the following DTCs occur: TP sensor, MAF sensor, vehicle speed sensor, ECT sensor.
- The engine speed is between 600 and 6250 RPM.
- The system voltage is between 11 and 16 volts.
- The ECT indicates an engine temperature between -7 °C (28 °F) and 120 °C (248 °F).
- The throttle angle is steady.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) the first time the fault is detected.
- If the misfire is severe enough to cause possible catalyst damage, the PCM will flash the MIL for as long as the misfire remains at catalyst damaging levels.
- The PCM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL "OFF" on the third consecutive ignition cycle in which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P0304 will clear after 40 consecutive ignition cycles occur without a fault.
- DTC P0304 can be cleared by using the Tech 2 "Clear Info" function or by disconnecting the PCM battery feed.

Diagnostic Aids
Check for the following conditions:
- System grounds - Ensure all connections are clean and properly tightened.
- Injector - Perform the injector coil/balance test to locate a faulty injector that contributes to a lean condition on the affected cylinder. In addition to the above test, check the condition of the injector O-ring.
- Faulty spark plug - Check for a cracked insulator, carbon tracking, incorrect gap, and worn electrodes.
- Damaged or faulty ignition coil - Check for cracks, carbon tracking or other damage.
- Substitute a known good coil - Swap the ignition coils and retest. If the misfire follows the coil, replace the ignition coil.

Steps 1 - 2:

Steps 3 - 7:

Steps 8 - 12:

Test Description