P0302
System Description
The Powertrain Control Module (PCM) monitors both the crankshaft and the camshaft position in order to detect an engine misfire. A rapid decrease in the crankshaft speed indicates misfire. The PCM may require that several consecutive misfire conditions are detected before storing this DTC and before illuminating the MIL. Under light misfire conditions, the PCM may require more than one trip to set this DTC. Under a severe misfire, the PCM flashes the MIL. A flashing MIL indicates that there is a misfire that is capable of damaging the catalytic converter. The Torque Converter Clutch disables momentarily in order to determine if the misfire was due to a rough road condition (automatic transmission only).
Conditions for Running the DTC
^ DTCs P0105, P0107, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0325, P0335, P0341, P0342, P0502, P0503, P0506, P0507, P0601, P0740, P0742, P1133, and P1621 not set.
^ The engine speed is between 469 RPM and 5900 RPM
^ The battery voltage is between 9 volts and 17 volts.
^ The Engine Coolant Temperature (ECT) is between -7°C (20°F) and 123°C (254°F).
^ The engine has been running more than 5 seconds.
^ The Throttle Position (TP) hasn't increased more than 8% in 1 second.
^ The Throttle Position (TP) hasn't decreased more than 1.5% in 1 second.
Conditions for Setting the DTC
The misfire total is more than 8 counts.
Action Taken When the DTC Sets
The Malfunction Indicator Lamp (MIL) illuminates if the fault is active within the same conditions for two out of eighty ignition cycles when there is a misfire
OR
The MIL illuminates after two consecutive ignition cycles in which the diagnostic runs with the fault being active
OR
The MIL illuminates immediately and flashes if a misfire is severe enough to cause any catalyst damage
^ The Torque Converter Clutch (TCC) disables when a misfire is present (automatic only)
^ The PCM records operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.
^ A history DTC stores.
^ The coolant fan turns ON.
Conditions for Clearing the MIL/DTC
^ The MIL turns OFF after three consecutive ignition cycles in which the diagnostic runs without a fault within the freeze frame conditions that the DTC failed.
^ A history DTC clears after 40 consecutive warm up cycles without a fault.
^ Clear the MIL/DTC(s) with a scan tool.
Diagnostic Aids
An intermittent can also be the result of a defective reluctor wheel. Remove crankshaft sensor and inspect reluctor wheel through sensor mount hole. Check for porosity and condition of the reluctor wheel.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.
2. Whenever a DTC P0108 is present, verify that no misfire is present by viewing the misfire counters. DTC P0108 may set as a result of a misfire.
3. A visual/physical inspection should include checking the following conditions:
^ The wiring for proper connections, pinches and cuts.
^ Clean and tight PCM grounds.
^ The vacuum hoses for splits, kinks and proper connections as shown on the Vehicle Emission Information label. Check thoroughly for any type of leak or restriction.
^ For air leaks at the throttle body mounting area and the intake manifold sealing surfaces.
4. This step determines if DTC P0302 is the result of a hard failure or an intermittent condition.
6. When the misfire is not present, operate the vehicle to the conditions found in the Freeze Frame Data in order to detect misfire. Depending on the engine load, the conditions may have to be maintained for up to 20 seconds. Whenever the misfire accumulators start to increment, then the misfire is present. A history misfire counter will store the number of misfires that have occurred until the DTC is cleared. The current counter must count a total of at least 195 misfires before writing to the history counter.
10. No spark on one coil, may be caused by an open secondary circuit. Therefore, the coil's secondary resistance should be checked.
13. Use the J 34730-2A to test the harness wiring and for PCM control of the injectors.
14. Perform the Fuel Inj Coil Test - ECT Between 10-35 Degrees C on the misfiring cylinder only.
16. Determines if the injector driver circuit is shorted to ground or voltage or if the PCM is malfunctioning.
20. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. The replacement PCM must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline procedures for PCM reprogramming and to the CKP System Variation Learn Procedure for the Crankshaft Position System Variation Learn Procedure.
22. Replace any spark plugs that are worn, cracked or fouled.
27. Since the voltage is supplied to the fuel injector on a single circuit before the injector harness, the malfunction could only be a poor connection or an open in the injector harness. An open before the harness would result in a Cranks But Won't Run complaint.
28. A basic engine problem that affects only cylinder #2 is possible at this point (i.e. valve train, compression, etc.).