Schematic Reference: Refer to Engine Controls Schematics
Circuit Description
The Powertrain Control Module (PCM) uses the crankshaft position sensor and camshaft position sensor to monitor changes in crankshaft rotation for each cylinder to determine a misfire. When the misfire rate equals or exceeds the count indicating that the engine condition has deteriorated, the MIL will light. If the misfire rate is high enough and the driving conditions will cause catalyst overheating, the MIL blinks when misfiring occurs.
Conditions for Setting the DTC
| • | Engine speed is between 200 and 1000 RPM |
| • | Battery voltage is between 9 volts and 17 volts. |
| • | Engine Coolant Temperature (ECT) is between -7° C (20° F) and 123°C (254°F). |
Action Taken When the DTC Sets
Malfunction Indicator Lamp (MIL) illuminates after two consecutive driving cycles with the fault active, which causes a deterioration in emission. The MIL will begin flashing if the misfire is severe enough to cause catalyst damage.
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present. |
| • | A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault. |
| • | A DTC can be cleared by using the scan tool Clear Information function or by disconnecting the PCM battery feed. |
Diagnostic Aids
| • | An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement. |
| • | Review "Misfire RPM" and "Misfire Load" located in the scan tool "Engine Data" list. This information can help determine the vehicle conditions when the misfire occurred. |
| • | The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set. |
| • | If DTC P0302 is intermittent, refer to Symptoms. |
| • | An intermittent can also be the result of a defective reluctor wheel. Remove crankshaft sensor and inspect reluctor wheel through sensor hole. Check for the condition of the wheel for porosity, nicks, dents etc. and repair as necessary. |
| • | Insure the power and ground to the PCM have a good, clean connections. |
| • | Check that EGR valve is operating properly, insure that the EGR is closing properly and not hanging open causing excessive EGR flow. |
| • | Check MAP sensor and ECT sensor typical scan for proper operation. |
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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Verifies whether the misfire is present. Misfire can sometimes be cause by a rough road condition.
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A vacuum leak can cause a lean misfire condition.
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This step is to verify if the misfire is cause by the ignition system.
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Contaminants in the fuel, such as alcohol or water, can create a misfire condition.
Step | Action | Value(s) | Yes | No | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Was the "Powertrain On Board Diagnostic (OBD) System Check performed? | -- | |||||||||||||||||
Does DTC P0302 set? | -- | Go to Diagnostic Aids | ||||||||||||||||
Did your inspection reveal a vacuum leak? | -- | |||||||||||||||||
Is adequate spark present? | -- | |||||||||||||||||
5 |
Was a repair necessary? | -- | ||||||||||||||||
6 |
Did the #2 ignition wire need replacement? | 25 000 ohms (25 K ohms) | ||||||||||||||||
7 |
Was a repair necessary? | -- | ||||||||||||||||
8 |
Was a repair necessary? | -- | ||||||||||||||||
9 |
Did the #2 spark plug need replacement? | -- | ||||||||||||||||
10 |
Is the fuel pressure within the specified value? | 206-255 kPa (31-37 psi) | ||||||||||||||||
Inspect for contaminated fuel. Refer to Engine Fuel. Is the fuel OK? (uncontaminated) | -- | |||||||||||||||||
12 | Replace contaminated fuel. Is action complete? | -- | -- | |||||||||||||||
13 |
Does the injector test light blink at the #2 injector harness connector? | -- | ||||||||||||||||
14 | Perform the Injector Coil Test/Balance Test Procedure, refer to Fuel Injector Coil Test/Fuel Injector Balance Test Procedure. Are injectors OK? | -- | ||||||||||||||||
15 |
Does the test light illuminate? | -- | ||||||||||||||||
16 |
Does the test light flash? | -- | ||||||||||||||||
17 | Replace any faulty injectors. Is action complete? | -- | -- | |||||||||||||||
18 | Check the #2 injector driver circuit for any of the following problems:
Was a problem found? | -- | ||||||||||||||||
19 | Repair the open or shorted injector driver circuit. Is the action complete? | -- | -- | |||||||||||||||
20 | Repair the open or short in the power feed wire to the #2 fuel injector. Is the action complete? | -- | -- | |||||||||||||||
21 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||||||||||||
22 |
Was a basic engine mechanical problem found and repaired? | -- | Go to Diagnostic Aids | |||||||||||||||
23 | After repairs, use the scan tool clear information function and road test vehicle within "Freeze Frame" conditions that set the DTC. Check for DTCs. Review scan tool data and if no DTCs are stored repair is complete. Are any DTCs displayed on scan tool? | -- | Go to the applicable DTC table | System OK |
