P0300

CIRCUIT DESCRIPTION
The Crankshaft Position (CKP) sensor sends pulses to the Powertrain Control Module (PCM) when the reluctor teeth rotate past the sensor. The PCM uses these pulses in order to synchronize ignition and fuel injector operation. The PCM also measures the interval between each pulse in order to determine if an excess change in the crankshaft speed has occurred A misfire causes an unwanted change in the crankshaft speed. A certain amount of crankshaft acceleration or of deceleration is expected between each firing stroke. If the crankshaft speed changes are more than an expected amount, the PCM will interpret this as misfire. If 2 percent or more of all cylinder firing events are misfires, the emission levels may exceed the mandated standards. The PCM monitors blocks of 200 engine revolutions and counts the number of misfires in each block.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0123, P0335, P0340, P0385, P0501, P0503, P1106, P1107, P1114, P1115, P1121, P1122, or P1336 are not set.
^ The engine speed is between 550-5,850 RPM.
^ The system voltage is 9-16 volts.
^ The ECT indicates an engine coolant temperature of -6°C ± 120°C (21°F-248°F).
^ The throttle angle is steady
^ The fuel level is more than 10 percent.
^ The decel fuel cutoff mode and the torque management are not active.

CONDITIONS FOR SETTING THE DTC
^ Five out of 16 consecutive 200-revolution blocks that contain 22 or more misfires is considered a non-catalyst damaging misfire.
^ Any 200-revolution block that contains an amount of misfire above a predetermined threshold is considered a catalyst damaging misfire.

ACTION TAKEN WHEN THE DTC SETS
^ If the misfire level is non-catalyst damaging, the PCM will illuminate the MIL during the second key cycle in which the DTC sets.
^ If the misfire is severe enough to cause catalyst damage, the PCM will flash the MIL while the misfire remains at damaging levels.
^ The PCM will disable the Torque Convener Clutch (TCC) operation.
^ The PCM stores the conditions present when the DTC set in the Freeze Frame and Failure Records.
^ Any data that was previously stored in the Freeze Frame will be overwritten if this DTC sets. The only exception to this is if an air fuel ratio DTC was already recorded in the Freeze Frame. In this case, the data stays in the Freeze Frame. The Misfire Data will be stored in the Failure Records.

CONDITIONS FOR CLEARING THE DTC
^ The PCM turns the MIL OFF after 3 consecutive trips that the diagnosis runs and does not fail. If the last failure was during a non-typical driving condition, the MIL may remain illuminated for more than 3 drive trips. Review the Freeze Frame for the last failure conditions.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared with the Clear Into function, or by disconnecting the PCM battery feed.

DIAGNOSTIC AIDS

NOTE: Refer to Connector Test Adapter kit J 35616-A Notice in Service Precautions

The scan tool provides information that can be useful in identifying the misfiring cylinder. If DTC P0300 is currently stored as Failed Since Code Clear, the misfire history counters will represent the level of misfire detected on each cylinder. The misfire counter values can be useful in determining if the misfire affects a single cylinder or is random. If the misfire is random, check for the following conditions:
^ Any CKP system variation data that is stored in the PCM that is incorrect. Run the CKP System Variation Learn Procedure.
^ A damaged accessory drive belt or a damaged belt-driven accessory. A damaged serpentine belt or a damaged belt-driven accessory can cause engine load variations sufficient to set a misfire DTC.
^ The air induction system. Any vacuum leaks that cause intake air to bypass the MAF sensor will cause a lean condition. Check for the following conditions:
- Any disconnected vacuum hoses or any damaged vacuum hoses
- A PCV valve that is incorrectly installed or is malfunctioning
- Any vacuum leaks at the throttle body
- Any vacuum leaks at the EGR valve
- Any vacuum leaks at the intake manifold mounting surfaces
^ The fuel pressure. Perform a fuel system pressure test. A faulty fuel pump, a restricted filter, or a faulty fuel pressure regulator will contribute to a lean condition. Refer to Fuel System Diagnosis. Component Tests and General Diagnostics
^ The fuel injectors. Refer to Fuel Injector Coil Test. Component Tests and General Diagnostics
^ A contaminated fuel supply. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool). Alcohol/Contaminants-In-Fuel Diagnosis (Without Special Tool) Alcohol/Contaminants-In-Fuel Diagnosis (With Special Tool)
^ The EGR system. Check for a leak which will contribute to a lean condition or to an excess EGR flow.
^ An extended idle. Excess Open Loop operation that is caused by extended idling or by short trip driving may leave deposits on the Heated Oxygen Sensors (HO2S). The deposits cause the sensors to respond slowly to the exhaust oxygen content, affecting fuel control, and causing a misfire to be indicated at idle. This condition is not permanent. In order to determine if this condition is causing DTC P0300 to set, review the Freeze Frame and the Failure Records for DTC P0300. If DTC P0300 occurs at high engine speeds, the condition that is described above did not cause the DTC to set. If the DTC occurs at low engine speeds and an ECT of less than 80°C (176°F), the condition may cause the DTC being set. The deposits on the HO2S can be eliminated by operating the warmed-up vehicle at a mass airflow of over 15 g/s.
^ Operating the vehicle with a low fuel level. This DTC may set if the vehicle misfires while running out of fuel. If a misfire is not present and the History Counters indicate random misfire was present, determine if the vehicle has been run out of fuel. If this is the case, further repair may not be necessary.

IMPORTANT: If the misfire was sufficient to cause catalyst damage and the MIL flashed, ensure the DTC P0420 test is passed after verifying the misfire repair.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs. This may assist in diagnosing the condition.

If the concern is intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1-12:

Steps 13-20:

The numbers below refer to the step numbers on the diagnostic table.
3. Engine misfire can change the engine load characteristics which may affect the TP sensor performance diagnosis. Before diagnosing DTC P0121, correct any misfire. The following conditions may cause a misfire DTC to be set: The CKP system variation is not learned. An intermittent CkP sensor concern. Incorrect rough road data from the Electronic Brake Control Module (EBCM). A faulty injector circuit. Before using the DTC P0300 diagnostic table, diagnose and repair any other DTCs.
4. The Misfire Current Cyl display may display a small amount of activity, but should not steadily increment during an entire test period.
5. A misfiring cylinder or a non-firing cylinder can sometimes affect the misfire counters for other cylinders. When performing this diagnosis, concentrate on the cylinder with the highest level of misfire, and correct the concern. This may also correct the other cylinders that indicate misfire. This step splits the test between the conditions that would cause a specific cylinder to misfire and the conditions that would affect all cylinders.