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 (TCC) disables momentarily in order to determine if the misfire was due to a rough road condition, automatic transmission only.
Conditions for Setting the DTC
| • | DTCs P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0325, P0335, P0341, P0342, P0404, P0405, P0502, P0503, P0506, P0507, P0601, P0740, P0742, P1133, P1404, and P1621 not set. |
| • | The misfire total is greater than 12 counts. |
| • | The engine speed is between 469 RPM and 6,000 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 15 seconds. |
| • | The Throttle Position (TP) hasn't changed more than 8% in 1 second. |
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 and a misfire is present. |
| OR |
| The MIL illuminates after two consecutive ignition cycles during in which the diagnostic runs with the fault active |
| OR |
| The MIL illuminates immediately and flashes if a misfire is severe enough to cause any catalyst damage. |
| • | In vehicles with automatic transmission only, the torque converter clutch (TCC) is disablesd when a misfire is present. |
| • | The PCM records the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
| • | The coolant fan turns ON. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutive ignition cycles during which the diagnostic runs without a fault present under the Freeze Frame conditions that existed when the DTC failed. |
| • | A history DTC clears after 40 consecutive warm up cycles without a fault. |
| • | Clear the MIL/DTCs 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
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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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.) Refer to the Engine Mechanical.
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Tests the ignition system voltage output using a J 26792 spark tester.
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Replace any spark plugs that are worn, cracked or fouled. Refer to Spark Plug Replacement in Engine Electrical 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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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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Before replacing the PCM, check the 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 learn procedure must be performed. Refer to PCM Replacement/Programming for PCM reprogramming and to the CKP System Variation Learn Procedure for the Crankshaft Position System Variation Learn Procedure .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
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)? | -- | |||
Check for a basic engine problem. Refer to Base Engine Misfire Diagnosis . Is the action complete? | -- | -- | ||
10 | 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? | -- | |||
14 | Perform the Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) . Are the fuel injectors OK? | -- | ||
15 |
Did the test light illuminate? | -- | ||
16 | Replace any malfunctioning fuel injectors. Refer to Fuel Injector Replacement . Is the action complete? | -- | -- | |
17 | Check the affected fuel injector driver circuit(s) for an open, short to ground or short to voltage. Was a problem found? | -- | ||
Repair the open or the shorted fuel injector driver circuit(s). Is the action complete? | -- | -- | ||
Repair the open ignition feed circuit between the fuel injector harness electrical connector and the fuel injector electrical connector. 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? | 30,000ohms | ||
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 light 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 light blink while cranking the engine? | -- | ||
25 | Check for poor electrical connections, if OK replace the ICM. Refer to Ignition Control Module Replacement . Is the action complete? | -- | -- | |
26 |
Was the PCM electrical connector malfunctioning? | -- | ||
Replace the PCM. Refer to PCM Replacement . Is the action complete? | -- | -- | ||
28 | Replace the spark plug wire. Refer to Wiring Repairs in Wiring Systems. Is 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 |
