System Description
The powertrain control module (PCM) uses information from the ignition control (IC) module and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring the variations in the crankshaft rotation speed for each cylinder the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the three-way catalytic converter (TWC) to overheat under certain conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for the TWC overheating are present.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0137, P0138, P0140, P0171, P0172, P0325, P0336, P0502, P0503, P0506, P0507, P0601, P0602, P1133, P1137, P1138, P1171, P1336, or P1621 are not set. |
| • | The engine speed is between 469-5,900 RPM. |
| • | The battery voltage is between 9-17 volts. |
| • | The engine coolant temperature (ECT) is between -7 to +123°C (20-254°F). |
| • | The engine has been running more than 5 seconds. |
| • | The throttle position (TP) has not increased more than 8 percent in 1 second. |
| • | The TP has not decreased more than 1.5 percent in 1 second. |
Conditions for Setting the DTC
The PCM is detecting a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standard.
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
An intermittent DTC can also be the result of a defective reluctor wheel. Remove the crankshaft position (CKP) sensor and inspect the reluctor wheel through the CKP sensor mount hole. Check the porosity and the condition of the reluctor wheel.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The misfire is considered random on all cylinders if, while viewing the misfire counters in the misfire data list, the misfire seems to move to different cylinders.
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The misfire is considered consistent if the misfire is occurring on the same cylinders consistently.
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When checking the spark at the spark plug wires, the spark should be consistent. A few sparks then nothing, is no spark.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 |
Important: Before clearing the DTCs, record the Freeze Frame/Failure Records for reference with a scan tool. This data will be lost when you use the Clear DTC information function. Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 | Install the scan tool. Are there any other DTCs stored? | -- | Go to Step 3 | |
3 |
Is the Misfire counter increasing? | -- | Go to Step 5 | Go to Step 4 |
4 |
Does the scan tool indicate a misfire is present? | -- | Go to Step 18 | |
Is the misfire random on all cylinders? | -- | Go to Step 10 | Go to Step 6 | |
Is the misfire consistent on specific cylinders? | -- | Go to Step 7 | -- | |
Does the tester indicate spark is consistent on all tested spark plug wires? | -- | Go to Step 8 | ||
8 |
Did you find a problem? | -- | Go to Step 17 | Go to Step 9 |
9 |
Did the misfires change cylinders? | -- | Go to Step 15 | Go to Step 11 |
10 |
Did you find a problem? | -- | Go to Step 18 | Go to Step 16 |
11 | Perform the Fuel Injector Balance Test. Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 . Did you find a problem? | -- | Go to Step 12 | Go to Step 17 |
12 |
Does the injector test lamp flash for each injector? | -- | Go to Step 13 | |
13 | Check the injector harness for a short to voltage between the PCM connector and the injector connector that failed the Balance Test using a DMM. Is the voltage above the specified value? | 0-1 V | Go to Step 14 | Go to Step 16 |
14 | Repair the short to voltage on the injector control circuit. Is the action complete? | -- | Go to Step 19 | -- |
15 | Replace the spark plugs. Refer to Spark Plug Replacement . Is the action complete? | -- | Go to Step 19 | -- |
16 | Physically and visually check for these conditions in the following order:
Repair as necessary. Did you find a problem? | -- | Go to Step 19 | Go to Step 17 |
17 |
Did you find a problem? | -- | Go to Step 19 | Go to Diagnostic Aids |
18 | Perform the CKP system variation learn procedure. Refer to Crankshaft Position System Variation Learn . Is the action complete? | -- | Go to Step 19 | -- |
19 |
Does the DTC run and pass? | -- | Go to Step 20 | Go to Step 2 |
20 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
