P0303

DTC P0301 - P0304

CIRCUIT DESCRIPTION
The engine control module (ECM) monitors changes in crankshaft speed using inputs from the crankshaft position (CKP) sensor. The ECM adjusts the fuel delivery amount to each cylinder in order to minimize crankshaft speed changes. If the ECM identifies a cylinder or cylinders requiring an excessive amount of fuel in order to maintain the correct crankshaft speed, it is considered misfire and DTC P0301 - P0304 will set depending upon which cylinder failed.

Condition for Running the DTC
- DTCs P0016, P0089, P0091, P0092, P0093, P0112, P0113, P0116, P0117, P0118, P0192, P0193, P0201, P0202, P0203, P0204, P0261, P0264, P0267, P0270, P0335, P0336, P0500, P0506, P0507, P0602, P0642, P0643, P1093, P1125, P1293, P2146, P2147, P2148, P2149, P2150, P2151, P2227, P2228 and P2229 are not set.
- The battery voltage is between 10-16 volts.
- The engine coolant temperature (ECT) is more than19 °F (-7 °C).
- The engine speed is between 500 -1050 RPM.
- The desired engine idle speed does not vary more than 100 RPM.
- The desired fuel injection quantity is between -30 -300 cu.mm.
- The vehicle speed is less than 2 MPH (3 km/h).

Condition for Setting the DTC
- The ECM detects that the fuel injection balancing rate is more than 30 cu.mm for longer than 70 seconds.

Action Taken When the DTC Sets
12,000 lbs GVW
- The ECM illuminates the malfunction indicator lamp (MIL) on the second consecutive driving cycle when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records on the second consecutive driving cycle when the diagnostic runs and fails.
- The ECM closes the EGR valve and holds to close position.

Except 12,000 lbs GVW
- The ECM will not illuminate the MIL when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.

Condition for Clearing the MIL/DTC
12,000 lbs GVW
- The ECM turns OFF the MIL after 3 consecutive driving cycles when the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic after the ECM turns OFF the MIL.
- Clear the MIL and the DTC with a scan tool.

Except 12,000 lbs GVW
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.

Diagnostic Aids
- An engine mechanical or fuel injector problem will cause this DTC(s) to set.
- Use a scan tool to observe the "Balancing Rate" for each cylinder at idle. A cylinder that is excessively large or small balancing rate may indicate incorrect fuel injector flow rate, faulty fuel injector(s), and weak or slightly seized cylinder.

NOTE: Each Diagnostic Trouble Code (DTC) agrees with the engine cylinder order.
P0301: Cylinder No. 1
P0302: Cylinder No. 2
P0303: Cylinder No. 3
P0304: Cylinder No. 4

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