System Description
The Powertrain Control Module (PCM) monitors both the crankshaft and camshaft position in order to detect engine misfire. The PCM looks for the rapid decrease in crankshaft speed associated with engine misfire once every 100 camshaft revolutions. The PCM may require that several consecutive misfire conditions are detected before storing this DTC and illuminating the MIL. Under light misfire conditions, the PCM may require more than one trip to set this DTC. Under severe misfire, the PCM flashes the MIL. A flashing MIL signals that a misfire capable of damaging the catalytic converter is detected. The Torque Converter Clutch is disabled momentarily to determine if the misfire was due to a rough road condition (automatic transmission only).
Conditions for Running the DTC
| • | No active MAP DTC's |
| • | No active IAT DTC's |
| • | No active ECT DTC's |
| • | No active TP DTC's |
| • | No active Oxygen Sensor DTC's |
| • | No active Fuel Trim DTC's |
| • | No active KS DTC's |
| • | No active CKP DTC's |
| • | No active CMP DTC's |
| • | No active VSS DTC's |
| • | No active IAC DTC's |
| • | No active PCM Memory DTC's |
| • | The engine has been running more than 5 seconds. |
| • | The engine speed is between 469 RPM and 5906 RPM |
| • | The Engine Coolant Temperature (ECT) is between -7°C (20°F) and 123°C (254°F). |
| • | The battery voltage is between 9 volts and 17 volts. |
| • | The fuel level is more than 10 percent. |
Conditions for Setting the DTC
The misfire total is more than 8 counts.
Action Taken When the DTC Sets
The Malfunction Indicator Lamp (MIL) will illuminate if the fault is active within the same conditions for two out of eighty ignition cycles when there is misfire.
OR
The MIL will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.
OR
| • | The MIL will illuminate immediately and flash if a misfire is severe enough to cause catalyst damage. |
| • | The Torque Converter Clutch (TCC) will disable whenever a misfire is being detected with or without a misfire DTC set (automatic transmission only). |
| • | The PCM will record the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault within the freeze frame conditions that the DTC failed. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | A scan tool can clear the DTCs. |
Diagnostic Aids
An intermittent DTC can also be the result of a defective reluctor wheel. Remove the crankshaft sensor and inspect the reluctor wheel through the crankshaft sensor mount hole. Check the porosity and the condition of the reluctor wheel.
Whenever the DTC is an intermittent, refer to the Driveability Symptom Tables.
Perform the fuel Injector Balance Test. Refer to Fuel Injector Balance Test .
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. This information on the scan tool can be referred to later.
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A visual/physical inspection should include checking the following components:
| • | The wiring for proper connections, pinches or cuts. |
| • | The PCM grounds for being clean and tight. |
| • | 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. |
| • | Check the throttle body mounting area and intake manifold sealing surfaces for air leaks. |
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When all the accumulators indicate misfire, then the misfire is being caused by something that affects the entire engine.
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If the misfire is not present, operate the vehicle within the conditions recorded 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 misfire is present. A history misfire counter will store the number of misfires that have occurred until the DTC is cleared.
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Check the fuel for contamination (water, alcohol, etc).
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Tests the ignition system voltage output using a spark tester.
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Replace any spark plugs that are worn, cracked or fouled. Refer to Ignition System if any plugs are fouled or damaged due to an engine mechanical malfunction.
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Checks for voltage at the ignition feed circuit.
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A basic engine problem that affects all cylinders is the only possibility at this point (e.g. cam timing, throttle body leak, restricted air flow, etc.).
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Whenever the fuel injector driver circuit is shorted to ground, the light will be ON steady. When the driver circuit is shorted to voltage or open, the light will be OFF.
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Since the voltage is supplied to the fuel injector on a single circuit, the malfunction could only be a poor electrical connection or an open in the fuel injector electrical harness. An open before the harness would result in a Cranks But Will Not Run complaint.
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The replacement PCM must be programmed and the crankshaft position system variation learn procedure must be performed. Refer to the latest Techline procedures for PCM programming.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check ? | -- | |||
2 | Install a scan tool. Is DTC P0200 set? | -- | ||
Were any repairs necessary? | -- | |||
4 |
Are any misfire current counters incrementing? | -- | ||
Was misfire present in all cylinders? | -- | |||
Are any misfire current counters incrementing? | -- | Go to Diagnostic Aids | ||
7 |
Is the fuel pressure within the specified range? | 284-325 kPa (41-47 psi) | Go to Fuel System Diagnosis | |
Check the fuel for contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . Is the fuel OK (uncontaminated)? | -- | |||
9 | Replace the contaminated fuel. Is the action complete? | -- | -- | |
Was spark observed on all four spark plug wires? | -- | |||
Were any spark plugs malfunctioning? | -- | |||
Does the fuel injector test light blink? | -- | |||
13 | Perform the Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) . Are the fuel injectors OK? | -- | ||
Check for a basic engine problem. Refer to Base Engine Misfire Diagnosis in Engine Mechanical. Is the action complete? | -- | -- | ||
15 |
Did the test lamp illuminate? | -- | ||
16 | Replace any malfunctioning fuel injectors. Refer to Fuel Injector Replacement . Is the action complete? | -- | -- | |
17 | Check the affected fuel injector driver circuits for an open, short to ground or short to voltage. Was a problem found? | -- | ||
Repair the open or the shorted fuel injector driver circuits. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | ||
Repair the open ignition positive voltage circuit between the fuel injector harness connector and the fuel injector connector. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | ||
20 | Measure the resistance of the spark plug wire that the spark plug tester did not spark. Is the resistance of the spark plug wire less than the specified value? | 1,000ohms/inch | ||
21 |
Notice: Do not leave the jumper wire connected to the PCM IC circuit connector for longer than 5 seconds at a time. Failure to do so may damage the ignition coil and/or the Ignition Control Module. Is spark present when the test lamp is removed from the IC circuit? | -- | ||
22 |
Was a repair necessary? | -- | ||
23 |
Is the secondary coil resistance within the specified value? | 5-8K ohms | ||
24 |
Did the test lamp blink while cranking the engine? | -- | ||
25 |
Is the action complete? | -- | -- | |
26 |
Was the PCM harness connector malfunctioning? | -- | ||
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
28 | Replace the spark plug wire. Refer to Spark Plug Wire Harness Replacement in Engine Electrical. Is the action complete? | -- | -- | |
29 | Replace the malfunctioning ignition coil. Refer to Ignition Control Module Replacement . Is the action complete? | -- | -- | |
30 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
31 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
