DTC P0300 Engine Misfire Detected. Chevrolet Corsica 1996

For 1990-2009 cars

Refer to

#### Ignition Controls

Engine Controls Components
Electronic Ignition (EI) System
Fuel Controls
Power, Ground, MIL, and DLC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
for wiring view.
Engine Controls Components
Fuel Controls
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### 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

• | Misfire total is greater than 12 counts.

• | Engine speed is between 469 RPM (automatic trans.) or 750 RPM (manual trans.) and 3400 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).

• | Engine has been running more than 15 seconds.

• | Throttle Position (TP) hasn't changed more than 8 % in 1 second.

• | DTC(s) P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0325, P0335, P0341, P0342, P0401, P0502, P0503, P0601, P0742, P1133, and P1406 not set.

### 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

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. 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 fault occurred. This information on the scan tool can be referred to later.

2. When a DTC P0108 is present, verify that no misfire is present by viewing the misfire counters. DTC P0108 may set as a result of misfire.

3. 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.

• | For air leaks at the throttle body mounting area and intake manifold sealing surfaces.

1. This determines if DTC P0300 is the result of a hard failure or an intermittent condition.

2. 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 two or more cylinders.

3. 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 starts to increment, then misfire is present. A history misfire counter will store the number of misfires that have occurred until the DTC is cleared. The current counter must count a total of at least 195 misfires before writing to the history counter.

4. Check fuel for water, alcohol, etc.

5. A basic engine problem that effects all cylinders is the only possibility at this point. (I.e. cam timing, throttle body leak, restricted air flow, etc.) Refer to Section 6A .

6. Tests the harness wiring and for PCM control of the fuel injectors using injector test light J 34780-2.

7. Checks for voltage at the ignition feed circuit.

8. 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.

9. Since voltage is supplied to the fuel injector on a single circuit, the fault could only be a poor connection or open in the fuel injector harness. An open before the harness would result in a Cranks But Will Not Run complaint.

10. Replace any spark plugs that are worn, cracked or fouled. Refer to Section 6A if any plugs are fouled or damaged due to an engine mechanical failure.

11. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Replacement PCMs must be reprogrammed. Refer to the latest Techline information for programming procedures.

#### DTC P0300 - Engine Misfire Detected

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are any component DTCs set? | -- | Go to DTC Tables first | Go to Step 3

3

1. Perform a visual/physical inspection.
2. Make any repairs that are necessary.

Were any repairs necessary?

--

Go to Step 34

Go to Step 4

4 | With the engine idling, install a scan tool. Are any Misfire Current counters incrementing? | -- | Go to Step 5 | Go to Step 6
5 | Are all counters equal (within a small percentage of each other)? | -- | Go to Step 7 | Go to Step 11

6

1. Ignition ON engine OFF, review the Freeze Frame data and note the parameters.
2. Operate the vehicle within the Freeze Frame conditions and condition for setting the DTC as noted.

Are any Misfire Current counters incrementing?

--

Go to Step 5

Go to Diagnostic Aids

7

1. Engine OFF.
2. Install a fuel pressure gauge.
3. Note the fuel pressure with the engine running.

Is the fuel pressure within the specified value?

214-303 kPa (31-44 psi)

Go to Step 8

Fuel System Diagnosis

8 | Check the fuel for contamination. Is the fuel OK (uncontaminated)? | -- | Go to Step 9 | Go to Step 10
9 | Check for a basic engine problem. Is the action complete? | -- | Go to Step 34 | --
10 | Replace the contaminated fuel. Is the action complete? | -- | Go to Step 34 | --

11

1. Engine OFF.
2. Disconnect the 4 fuel injector connectors from the injectors.
3. Install an injector test light on the injector harness connector for the cylinders that had misfired.
4. Crank the engine and note the test light.

Does the injector test light blink?

--

Go to Step 12

Go to Step 13

12 | Perform the Injector Coil Test Procedure , refer to Fuel Injector Solenoid Coil Test Are the fuel injectors OK? | -- | Go to Step 14 | Go to Step 16

13

1. Disconnect the injector test light.
2. With a test light connected to ground, probe the ignition feed terminal of the injector harness connector for each cylinder that had misfire.
3. Crank the engine.

Did the test light illuminate?

--

Go to Step 17

Go to Step 26

14

1. Ignition OFF
2. Disconnect the fuel injector harness connector.
3. Install spark tester J 26792 on cylinder #1 spark plug cable.
4. Crank the engine and check for spark.
5. Repeat the above procedure on cylinders #2, #3, #4.

Was spark observed on all four spark plug cables?

--

Go to Step 29

Go to Step 20

15

1. Ignition OFF.
2. Disconnect the fuel injector harness connector.
3. Disconnect the 6-way connector at the Ignition Control Module (ICM).
4. With a J 39200 connected to ground, probe ICM harness connector terminal D then ICM terminal E while cranking the engine.

Are the frequency readings within the specified values?

1-10 Hz

Go to Step 22

Go to Step 21

16 | Replace any faulty fuel injector(s). Is the action complete? | -- | Go to Step 34 | --
17 | Check the effected fuel injector driver circuit(s) for an open, short to ground or short to voltage. Was a problem found? | -- | Go to Step 18 | Go to Step 19
18 | Repair the open or the shorted fuel injector driver circuit(s). Is the action complete? | -- | Go to Step 34 | --
19 | Replace the PCM. Is the action complete? | -- | Go to Step 34 | --
20 | Measure the resistance of the spark plug cable that the spark plug tester did not spark. Is the resistance of the spark plug cable less than the specified value? | 30000 ohms | Go to Step 15 | Go to Step 32

21

1. Ignition ON Engine OFF.
2. With a DVM connected to ground probe the ICM harness connector cavity that did not show frequency response.

Is the voltage less than the specified value?

0.5 V

Go to Step 23

Go to Step 27

22 | Remove the ignition coil from the cylinder that did not show a frequency response. Using a DVM measure the secondary coil resistance. Is the secondary coil resistance within the specified value? | 5-8K ohms | Go to Step 24 | Go to Step 30

23

1. Ignition OFF
2. With a test light connected to B+, probe the cavity that did not show a frequency response.

Does the test light?

--

Go to Step 33

Go to Step 25

24

1. Install a known good ignition coil.
2. Reconnect the ICM connector.
3. With the spark tester connected to the problem cylinder crank the engine and observe the spark tester.

Was spark observed on the spark tester?

--

Go to Step 30

Go to Step 28

25 | Repair the open in the effected ignition control circuit. Is the action complete? | -- | Go to Step 34 | --
26 | Repair the open ignition feed circuit. Is the action complete? | -- | Go to Step 34 | --
27 | Repair the short to voltage in the effected ignition control circuit. Is the action complete? | -- | Go to Step 34 | --
28 | Replace the ICM. Is the action complete? | -- | Go to Step 34 | --
29 | Replace any faulty spark plugs. Is the action complete? | -- | Go to Step 34 | --
30 | Replace the faulty ignition coil. Is action complete? | -- | Go to Step 34 | --
31 | Replace the PCM. Is the action complete? | -- | Go to Step 34 | --
32 | Replace the spark plug cable. Is the action complete? | -- | Go to Step 34 | --

33

1. Check Ignition control circuit A and Ignition control circuit B for a short to ground.
2. Repair as necessary.

Was a problem found?

--

Go to Step 34

Go to Step 31

34

1. Using the scan tool, clear the DTCs.
2. Start the engine and idle at normal operating temperature.
3. Operate the vehicle within the conditions for setting this DTC as supported in the text.

Does the scan tool indicate that this diagnostic ran and passed?

--

Go to Step 35

Go to Step 2

35 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC Table | System OK