System Description
The engine control module (ECM) monitors the crankshaft and camshaft positions to detect if the engine is misfiring. The ECM looks for a quick drop in crankshaft speed. This test is executed in blocks of 100 engine revolution tests. It may take between one to several tests to store a DTC and illuminate the malfunction indicator lamp (MIL). Under light misfire conditions, it may also take more than one trip to set a DTC. Severe misfire will flash the MIL, indicating that catalyst damage is possible.
Conditions for Setting the DTC
| • | The emission threshold is 3 percent for manual transaxle. |
| • | Twenty engine cycles have occurred since cranking has started. |
| • | The A/C compressor clutch has not just engaged or disengaged. |
| • | Engine load and engine speed is in a detectable region and is at or above 0 torque. |
| • | The camshaft position (CMP) sensor is in synchronization. |
| • | The exhaust gas recirculation (EGR) flow diagnostic is not in progress. |
| • | The fuel level is greater than 20 percent of rated tank capacity. |
| • | Decel fuel cut-off (DFCO) is not active. |
| • | Fuel is not shut-off from high engine speed of 6,500 RPM for manual transaxle vehicles. |
| • | Fuel is not shut-off at 255 km/h (158 mph). |
| • | Throttle position change is less than 3 percent per 125 ms. |
| • | The vehicle has not encountered an abusive engine speed of 7,000 RPM. |
| • | Crankshaft speed patterns are normal. |
| • | Throttle position is less than 4 percent when vehicle speed is greater than 10 km/h (6 mph). |
| • | Engine speed is between 600-6,500 RPM. |
| • | Vehicle voltage is between 11-16 volts. |
| • | Engine coolant temperature (ECT) is between -7 to +120°C (+20 to +248°F). |
| • | The engine speed is less than or equal to 1,600 RPM or the crank angle sensing error has not been learned. |
| • | There is the correct ratio between crankshaft position (CKP) sensor pulses and CMP sensor pulses. |
| • | DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0336, P0337, P0341, P0342, and P0502 are not set. |
Action Taken When the DTC Sets
| • | The MIL will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| OR |
| • | The MIL will illuminate immediately and flash if misfire is present. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 4 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. |
| • | The DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
An intermittent can also be the result of a defective reluctor wheel. Remove the CKP sensor and inspect the reluctor wheel through the sensor mount hole. Inspect for porosity and the condition of the wheel. If the DTC is intermittent, refer to Symptoms - Engine Controls .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Diagnostic 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 on the scan tool for later reference.
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When all the accumulators are relatively equal, then the misfire is being caused by something that affects the entire engine. When they are not, then the misfire is being caused by something that is specific to 2 or more cylinders.
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Whenever the misfire is not present, operating the vehicle may be necessary to duplicate the conditions 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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Inspect the fuel for water, alcohol, etc.
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A basic engine problem that affects all cylinders is the only possibility at this point, such as cam timing, throttle body leak, restricted airflow, etc.
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This step tests the ignition system voltage output using a spark tester.
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Replace any spark plugs that are worn, cracked, or fouled.
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This step checks for voltage at the ignition feed circuit.
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Whenever the 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 voltage is supplied to the fuel injector on a single circuit, the malfunction could only be a poor connection or open in the fuel injector harness. An open before the harness would result in an Engine Cranks But Will Not Run complaint.
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Before replacing the ECM, inspect the terminals for improper mating, broken locks, or physical damage to the wiring harness. The replacement ECM must be programmed. Refer to the latest Techline procedure for ECM reprogramming.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | ||||||||||
2 |
Are DTCs P0202 or P0300 set? | -- | Go to Step 3 | |||||||||
3 |
Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 4 | ||||||||
4 | Start the engine and allow it to idle. Are any misfire current counters incrementing? | -- | Go to Step 5 | Go to Step 6 | ||||||||
Are all counters equal, within a percentage of each other? | -- | Go to Step 7 | Go to Step 11 | |||||||||
Are any misfire current counters incrementing? | -- | Go to Step 5 | Go to Diagnostic Aids | |||||||||
7 |
Is the fuel pressure within the specified range? | 379-393 kPa (55-57 psi) | Go to Step 8 | Go to Fuel System Diagnosis | ||||||||
Inspect the fuel for contamination. Is the fuel OK? | -- | Go to Step 9 | Go to Step 10 | |||||||||
Inspect for a basic engine problem and repair as necessary. Did you find and correct the condition? | -- | Go to Step 27 | -- | |||||||||
10 | Replace the contaminated fuel. Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
Is a spark observed on all 4 spark plug cables? | -- | Go to Step 12 | Go to Step 20 | |||||||||
Replace the malfunctioning spark plug. Did you complete the replacement? | -- | Go to Step 27 | Go to Step 13 | |||||||||
Does the injector test light blink? | -- | Go to Step 14 | Go to Step 15 | |||||||||
14 | Perform the Fuel Injector Balance Test. Refer to Fuel Injector Balance Test with Special Tool . Are the fuel injectors OK? | -- | Go to Step 9 | Go to Step 16 | ||||||||
15 |
Does the test light illuminate? | -- | Go to Step 17 | Go to Step 19 | ||||||||
16 | Replace the malfunctioning fuel injector. Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
17 | Inspect the affected fuel injector driver circuit for an open, short, or short to voltage. Is a repair necessary? | -- | Go to Step 18 | Go to Step 24 | ||||||||
Repair the open or the shorted fuel injector driver circuit. Did you complete the repair? | -- | Go to Step 27 | -- | |||||||||
Repair the open ignition feed circuit between the fuel injector harness connector and the fuel injector connector. Did you complete the repair? | -- | Go to Step 27 | -- | |||||||||
20 | Measure the resistance of the spark plug cable. Is the resistance of the spark plug cable less than the specified value? | 30,000 ohms | Go to Step 21 | Go to Step 25 | ||||||||
21 | Inspect the ECM connector and connections. Are the connections OK? | -- | Go to Step 22 | Go to Step 23 | ||||||||
22 | Inspect the affected cylinders ignition control circuit for an open or short and repair as needed. Did you find and correct the condition? | -- | Go to Step 27 | Go to Step 26 | ||||||||
23 | Repair the connector or connections. Did you complete the repair? | -- | Go to Step 27 | -- | ||||||||
24 |
Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
25 | Replace the spark plug cable. Did you complete the replacement? | -- | Go to Step 27 | -- | ||||||||
26 | Replace the faulty ignition coil. Did you complete the replacement? | -- | Go to Step 27 | Go to Step 24 | ||||||||
27 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | Go to Step 28 | Go to Step 2 | ||||||||
Are any DTCs displayed that have not been diagnosed? | -- | System OK |
