DTC P0301 Cylinder 1 Misfire Detected. Chevrolet Metro 1999

For 1990-2009 cars

Refer to

#### Cell 21: Ignition System

and to

#### Cell 21: CMP Sensor and CKP Sensor

.

### Circuit Description

The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensor and from the camshaft position (CMP) sensor in order to determine if an engine misfire is occurring. By monitoring changes in the crankshaft rotation for each cylinder the PCM counts individual misfire events. The malfunction indicator lamp (MIL) illuminates if the misfire rate equals or exceeds a preset count. A misfire rate that is high enough can cause the catalytic converter to overheat under certain driving conditions. The MIL flashes on and off if the conditions for catalytic converter overheating are present.

### Conditions for Running the DTC

• | The engine coolant temperature is between -10°C and +110°C (14°F-230°F).

• | The intake air temperature is between -10°C and +70°C (14°F-158°F).

• | The barometric pressure is more than 75 kPa.

• | The TP sensor change is less than 1.9 degrees per 16 firing events.

• | The change in the manifold absolute pressure (MAP) is less than 1.3 kPa in 60 firing events.

• | The engine speed is less than 6,500 RPM, and the change in engine speed is less than 200 / 50 msec.

### Conditions for Setting the DTC

• | The misfire rate at 200 engine revolutions is more than a specified value.

• | The misfire rate at 1,000 RPM is more than a specified value.

• | The conditions are present from 5 seconds after the engine is started to 1 second before the fuel shut-off.

### Action Taken When the DTC Sets

• | The PCM flashes the MIL the first time catalyst damaging misfire occurs.

• | The PCM illuminates the MIL the second time emission thresholds are exceeded and the diagnostic fails.

• | The PCM records the operating conditions at the time that the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the DTC

• | The MIL turns OFF after three consecutive trips during which the diagnostic runs and does not detect a fault.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the Clear DTC Information function of the scan tool, or disconnect the PCM battery feed in order to clear the DTC.

### Diagnostic Aids

Check for any of the following conditions:

• | Before diagnosing misfire DTCs, diagnose other DTCs.

• | Check for the engine overheating.

• | Check for engine vacuum leaks.

• | Check for a PCV system malfunction. Perform a functional check of the PCV valve. Refer to Crankcase Ventilation System Inspection .

• | Inspect for an intermittent malfunction that is caused by the spark plugs, by the ignition wires, or by the ignition coil. Check the ignition system performance with an engine oscilloscope.

• | Fuel pressure that is out of specification Refer to Fuel System Diagnosis .

• | A fuel injector malfunction may cause DTC P0301 to set. Check the performance of the fuel injectors. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) and Sequential Multiport Fuel Injector Balance Test to .

• | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | An engine mechanical malfunction.Measure the engine cylinder compression and the valve lash adjustment in order to compare the measurements to OEM specifications. Refer to Engine Compression Test in Engine Mechanical.

| .

• | Inspect the applicable wiring harness for damage, and repair the harness as necessary.

• | A misfire DTC may be the result of a faulty signal rotor on the crankshaft timing belt pulley. Remove the crankshaft position (CKP) sensor, and inspect the crankshaft signal rotor through the sensor hole. Check the signal rotor for foreign material and for damaged teeth.

An intermittent fault may be induced by wetting the secondary ignition system with water before operating the vehicle under the conditions that set the DTC.

If DTC P0301 cannot be duplicated, the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable Freeze Frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.

2. This step determines if a fault is present.

3. The #1 ignition coil provides the spark for cylinders 1 and 4 simultaneously. Any condition that effects the ignition circuit of cylinder 4 may also have an effect on the ignition circuit of cylinder 1. Inspect both sides of the ignition coil for cracks, for carbon tracking, and for corrosion.

4. The ignition coil may have an internal fault.

5. This step checks for the electrical signal from the PCM for the operation of the fuel injector. If the injector test lamp does not illuminate, the fuel injector control circuit is diagnosed for a faulty condition.

6. A faulty fuel injector can cause a misfire condition and a DTC P0301 to set.

7. This step checks for a mechanical fault as the cause of the misfire condition. Low engine compression and an incorrect valve lash may also cause a rough idling condition.

8. This step checks for a faulty crankshaft signal rotor. Visually inspect the teeth of the signal rotor through the CKP sensor aperture for damage, for foreign material, and for misalignment.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On--Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Start the engine. Is a misfire present at idle? | -- | Go to Step 4 | Go to Step 3

3

1. Install a scan tool.
2. Turn ON the ignition, leaving the engine OFF.
3. Clear the scan tool information.
4. Operate the vehicle within the Freeze Frame data as noted.

Is DTC P0301 set?

--

Go to Step 4

Go to Diagnostic Aids

4

1. Inspect for any of the following conditions:

• | A PCV valve that is incorrectly operating or is leaking

• | An incorrect PCV valve

• | A vacuum leak at the intake manifold or a gasket

• | A vacuum leak at a cracked vacuum hose, at a split vacuum hose, or at a worn vacuum hose

2. Repair as necessary.

Was a repair necessary?

--

Go to Step 17

Go to Step 5

5

1. Install the J 26792 spark tester or an equivalent at the end of the #1 cylinder ignition wire.
2. Crank the engine while observing the spark tester.

Is a blue spark present?

--

Go to Step 10

Go to Step 6

6

1. Remove the #1 ignition wire.
2. Inspect the #1 ignition wire for any of the following conditions:

• | Carbon tracking

• | Insulation damage

• | Corroded terminals

3. Repair as necessary.

Was a repair necessary?

--

Go to Step 17

Go to Step 7

7

1. Measure the resistance of the #1 ignition wire with a DMM.
2. Replace the #1 ignition wire if the resistance is more than the specified value.

Did you replace the #1 ignition wire?

1.2k -3.0k ohms/ft

Go to Step 17

Go to Step 8

8

1. Inspect the #1 ignition coil for any of the following conditions:

• | Cracks

• | Moisture

• | Faulty electrical connections

• | Carbon tracking

• | Corrosion

2. Repair as necessary.

Was a repair necessary?

--

Go to Step 17

Go to Step 9

9 | Replace the #1 ignition coil. Refer to Ignition Coil Replacement . Is the action complete? | -- | Go to Step 17 | --

10

1. Remove the #1 spark plug. Refer to Spark Plug Replacement in Engine Electrical.
2. Inspect the spark plug for any of the following conditions:

• | Oil fouling

• | Fuel fouling

• | Evidence of coolant in the cylinder

• | An incorrect gap

• | Missing platinum pads

• | A loose center electrode

• | Cracked porcelain

• | Carbon tracking

• | Loose terminal end

3. Replace the spark plug as necessary.

Did you replace the #1 spark plug?

--

Go to Step 13

Go to Step 11

11

1. Turn OFF the ignition.
2. Disconnect the electrical connector to the #1 fuel injector.
3. Install a J 34730-2B injector test lamp or an equivalent into the harness connector of the #1 fuel injector.
4. Observe the injector test lamp while cranking the engine.

Did the injector test lamp flash while cranking the engine?

--

Go to Step 12

Go to Fuel Injector Circuit Diagnosis

12 | Check the #1 fuel injector for correct operation. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) and to Sequential Multiport Fuel Injector Balance Test . Was a faulty fuel injector found and replaced? | -- | Go to Step 17 | Go to Step 14
13 | Was the spark plug replaced because of fuel, oil, or coolant fouling? | -- | Go to Step 14 | Go to Step 17

14

1. Check for any of the following engine mechanical concerns that could affect the #1 cylinder:

• | A worn camshaft or a faulty camshaft

• | Leaking valves or sticking valves

• | Excessive valve deposits

• | Broken piston rings or leaking piston rings.

• | Weak valve springs

• | Incorrect valve timing

• | Intake leaks

• | A leaking head gasket

• | A loose motor mount or a broken motor mount.

2. Repair as necessary. Refer to Engine Compression Test in Engine Mechanical.

Was a basic engine mechanical concern found and repaired?

--

Go to Step 17

Go to Step 15

15

1. Remove the CKP sensor. Refer to Crankshaft Position Sensor Replacement .
2. Visually inspect the CKP sensor for the following conditions:

• | Physical damage

• | Foreign material on the sensor surface

• | Water or corrosion at the electrical terminals

3. Repair as necessary.

Was a repair necessary?

--

Go to Step 17

Go to Step 16

16

1. Inspect the CKP sensor signal rotor on the crankshaft timing belt pulley for the following conditions:

• | Damaged teeth

• | Foreign material

• | Correct installation

2. Repair as necessary.

Was a repair necessary?

--

Go to Step 17

Go to Diagnostic Aids

17

1. Perform the Clear DTC Information function on the scan tool, and road-test the vehicle within the Freeze Frame conditions which set the DTC.
2. Review the scan tool data, and check the data for DTCs. The repair is complete if no DTCs are displayed.

Does the scan tool display any DTCs?

--

Go to the applicable DTC table

System OK