P0304

DTC P0301, P0302, P0303, P0304 - Cylinder (1, 2, 3, 4) Misfire Detected

Diagnostic Chart:

Schematic:

The PCM uses pulses from the crankshaft position sensor to determine the position and rpm of the engine at various degrees of rotation. The PCM can then base misfire diagnostics on the principle that crankshaft velocity will increase as each cylinder contributes its power input. Under certain conditions the PCM will perform a series of tests to determine misfire percentage on a cylinder based on crankshaft velocity variation. The MIL (SERVICE ENGINE SOON) light will flash if an active catalyst damaging misfire occurs (20-100%) and will illuminate On solid if an emission related misfire (2-19%) is present after two consecutive trips. The MIL (SERVICE ENGINE SOON) light will turn Off after three consecutive passed trips meeting the same misfire criteria. The torque converter is disabled momentarily to determine if the misfire was due to a rough road condition (automatic only).

DTC PARAMETERS
DTC P0301 (Cylinder 1), or DTC P0302 (Cylinder 2), or DTC P0303 (Cylinder 3), or DTC P0304 (Cylinder 4) will set if a misfire has been detected after a series of tests when:
^ More than 12 misfire counts.
^ Engine speed is between 469 or 6400 rpm.
^ Engine coolant is between -7° and 123°C (20° and 254°F).
^ Fuel level is greater than 10%.
^ The engine has been running at least 5 seconds.
^ Ignition voltage is between 9-17 volts.
^ No TP Sensor, CKP IAT MAP ECT O2 sensor, Fuel Trim Lean/Rich, Knock, CMP VSS, Idle Speed HI/LOW, ECM Memory, TCC, and PCM Long Term Memory DTCs have been set.

IMPORTANT: The misfire diagnostics are continually checked with engine running when the above conditions have been met.

DIAGNOSTIC AIDS
If an injector or ignition system DTC is active and the misfire DTC is active, diagnose the other DTCs first.

Use the Scan tool to monitor current misfire counts. The Scan tools current misfire counts should pick up an intermittent misfire problem. Watch the misfire counter. If a specific cylinder misfires under certain load conditions, it may be duplicated in the stall.
^ Injector resistance - 12-13 ohms
^ Spark plug gap - 0.045 in.