P0301
P0301 - CYLINDER #1 MISFIRE
When Monitored and Set Condition
- When Monitored: Any time the engine is running, and the Target Learning Coefficient has been successfully updated.
- Set Condition: When more than a 1.0% misfire rate is measured during two trips.
For a complete Powertrain Control Module Circuit Diagram, Schematics and Diagrams.
Diagnostic Test
1. PRE-DIAGNOSTIC CHECK OUT
NOTE: Always perform diagnostics with a fully charged battery.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.
NOTE: Check for applicable TSBs related to the problem.
Turn the ignition on.
With the scan tool, read PCM DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors. Repair as necessary.
Perform this procedure prior to symptom diagnosis.
Continue
- Go To 2
2. CHECK FOR CURRENT DTC
NOTE: If other engine DTCs are present with this DTC, diagnose all other engine DTCs before continuing.
NOTE: If the PCM detects and stores a DTC, the PCM also stores the engine/vehicle operating conditions under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the DTC is displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for a DTC.
Turn the ignition on.
With the scan tool, erase PCM DTCs.
NOTE: It maybe necessary to road test the vehicle for this DTC to set.
With the scan tool, read PCM DTCs.
Did this DTC set again?
Yes
- Go To 3
No
- Go To 17
3. VISUAL AND PHYSICAL INSPECTION
NOTE: Reviewing the vehicle repair history may aid in the repair of the misfire condition.
Visually and physically inspect the engine for any of the following conditions.
- Worn serpentine belt
- Binding Engine-Driven accessories.
- Misaligned water pump, P/S pump and A/C compressor pulleys
- Improper CKP Sensor mounting
- Poor connector/terminal to component connection, i.e., CKP Sensor, Fuel Injector, Coil On Plug, etc.
- Vacuum leaks
- Restricted Air Intake system
NOTE: Ensure the powers and grounds for the PCM are functioning properly.
Were any of the above conditions present?
Yes
- Repair as necessary.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- Go To 4
4. IGNITION SYSTEM OPERATION
Turn the ignition off.
Remove the Fuel Pump Fuse from the Relay Control Module.
Disconnect the Coil On Plug harness connector.
Remove the Coil On Plug.
NOTE: Before continuing, inspect the Coil On Plug for the following conditions. Damage or Carbon Tracking on the Coil On Plug or the spark plug insulator boot. If a problem is found, replace the Coil On Plug. Ignition Coil - Removal.
Install spark testers to one of the Coil On Plug wires.
Reconnect the Coil On Plug harness connector to the Coil On Plug.
While cranking the engine, observe the spark coming from the spark testers.
NOTE: A crisp blue spark should be generated that is able to jump the gap of the spark testers.
NOTE: Before continuing with next Step, reinstall Fuel Pump Fuse in the Relay Control Module.
Is good spark present?
Yes
- Go To 5
No
- Go To 14
5. SPARK PLUG
Turn the ignition off.
Remove the Spark Plug.
Inspect the Spark Plug for the following conditions.
- Cracks
- Carbon Tracking
- Foreign Material
- Gap size out of specifications
- Loose or broken electrode
NOTE: Lightly tap the bottom of the spark plug on a solid surface. The electrode in the spark plug should not move.
Were any of the above condition present?
Yes
- Replace the Spark Plug. Spark Plug - Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- Go To 6
6. CHECKING FOR POSSIBLE MECHANICAL PROBLEM
Turn the ignition off.
Check for any of the following conditions/mechanical problems.
ENGINE VACUUM - must be at least 330 mm Hg (13 in. Hg) in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
ENGINE PCV SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - must not have internal vacuum leaks
FUEL - must be free of contamination
Are there any engine mechanical problems?
Yes
- Repair as necessary.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- Go To 7
7. CHECKING FUEL PRESSURE
WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF). BEFORE TESTING OR SERVICING ANY FUEL SYSTEM HOSE, FITTING OR LINE, THE FUEL SYSTEM PRESSURE MUST BE RELEASED.
With the ignition off.
Install a fuel pressure gauge to the fuel rail.
Start the engine and observe the fuel pressure reading.
NOTE: Fuel pressure specification is 3.7 to 4.2 bar (54 to 61 psi).
Choose a conclusion that best matches your fuel pressure reading.
Within Specification
- Go To 8
Below Specification
- Go To 12
Above Specification
- Replace the fuel filter/pressure regulator. Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
8. CHECKING FUEL LEAK DOWN
WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF). BEFORE TESTING OR SERVICING ANY FUEL SYSTEM HOSE, FITTING OR LINE, THE FUEL SYSTEM PRESSURE MUST BE RELEASED.
NOTE: Before continuing visually and physically inspect the fuel delivery system for external leaks or damage. Repair/replace as necessary.
Turn the ignition off.
Install a substitute fuel pressure hose between the fuel pump and fuel filter.
Start the engine and allow the fuel system to reach maximum pressure.
Turn the ignition off.
Using Special Tool #C4390, Hose Clamp Pliers, slowly clamp off the substitute fuel pressure hose between the fuel pump and the fuel filter.
Monitor the fuel pressure gauge for a minimum of 5 minutes.
NOTE: The pressure should not fall below 3.0 bar (44 psi) within 5 minutes and should not fall below 2.5 bar (36 psi) within 30 minutes.
Does the fuel pressure gauge fall below the above specification?
Yes
- Replace the leaking component between the Fuel Pump and Injector(s).
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- Go To 9
NOTE: Remove the hose clamp pliers before continuing with test.
9. ENGINE CONTROL RELAY OUTPUT CIRCUIT
Turn the ignition off.
Disconnect the Fuel Injector harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Using a 12-volt test light connected to ground, probe the Engine Control Relay Output circuit at the Fuel Injector harness connector.
Does the test light illuminate brightly?
Yes
- Go To 10
No
- Repair the Engine Control Relay Output circuit for an open.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
10. FUEL INJECTOR
With the ignition on.
Using a 12-volt test light connected to 12-volts, probe the Fuel Injector Control circuit.
With the scan tool, actuate the Fuel Injector Kill.
Does the test light blink?
Yes
- Replace the Fuel Injector. Fuel Injector - Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- Go To 11
11. FUEL INJECTOR CONTROL CIRCUIT
Turn the ignition off.
Disconnect the PCM harness connector(s).
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance of the Fuel Injector Control circuit from the Fuel Injector harness connector to the PCM harness connector.
Is the resistance below 5.0 ohms?
Yes
- NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary. Replace and program the Powertrain Control Module. Powertrain Control Module - Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- Repair the Fuel Injector Control circuit for an open.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
12. RESTRICTED FUEL SUPPLY LINE
WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF). BEFORE TESTING OR SERVICING ANY FUEL SYSTEM HOSE, FITTING OR LINE, THE FUEL SYSTEM PRESSURE MUST BE RELEASED.
Turn the ignition off.
Raise vehicle on hoist and disconnect the fuel pressure line at the fuel pump.
Attach a fuel pressure test gauge.
Turn the ignition on.
With the scan tool, actuate the Fuel Pump Relay and observe the fuel pressure gauge.
NOTE: Fuel pressure specification is 3.7 to 4.2 bar (54 to 61 psi).
Is the fuel pressure within specification?
Yes
- Repair or replace fuel supply line as necessary.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- Go To 13
13. FUEL STRAINER
WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF). BEFORE TESTING OR SERVICING ANY FUEL SYSTEM HOSE, FITTING OR LINE, THE FUEL SYSTEM PRESSURE MUST BE RELEASED.
Turn the ignition off.
Remove the and inspect the Fuel Strainer.
Is the Fuel Strainer plugged?
Yes
- Replace the Fuel Strainer. Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- NOTE: Before continuing, check the Fuel Pump Module harness connector terminals for corrosion, damage, or terminal push out. Ensure the ground circuit is operating properly. Repair as necessary. Replace the Fuel Pump. Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
14. FUSED IGNITION SWITCH OUTPUT CIRCUIT
Turn the ignition off.
Disconnect the Coil On Plug harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Using a 12-volt test light connected to ground, probe the Fused Ignition Switch Output circuit at the Coil On Plug harness connector.
Does the test light illuminate brightly?
Yes
- Go To 15
No
- Repair the Fused Ignition Switch Output circuit for an open.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
15. COIL ON PLUG
Turn the ignition off.
Remove the Fuel Pump Fuse from the Relay Control Module.
Using a 12-volt test light connected to 12-volts, probe the Coil On Plug Driver circuit.
Crank the engine for 5 second while observing the test light.
Does the test light blink/flicker?
Yes
- Replace the Coil On Plug. Ignition Coil - Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- Go To 16
16. COIL ON PLUG DRIVER CIRCUIT
With the ignition off.
Disconnect the PCM harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Check the Coil On Plug Driver circuits for a short to voltage, short to ground, or open.
Was a problem found with the Coil On Plug Driver circuits?
Yes
- Repair the Coil On Plug Driver circuits for the problem found.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary. Replace and program the Powertrain Control Module. Powertrain Control Module - Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
17. INTERMITTENT MISFIRE
NOTE: The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.
WARNING: WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
Search for any Technical Service Bulletins (TSBs) that may apply.
With the engine running at normal operating temperature, monitor the scan tool parameters related to the DTC while wiggling the wire harness. Look for parameter values to change and/or a DTC to set.
Visually inspect the related wire harness. Look for any chafed, pierced, pinched, partially broken wires and broken, bent, pushed out, or corroded terminals.
Inspect and clean all PCM, engine, and chassis grounds.
NOTE: Reviewing the vehicle repair history may aid in the repair of the misfire condition.
Visually and physically inspect the engine for any of the following conditions.
- Worn serpentine belt
- Binding Engine-Driven accessories.
- Misaligned water pump, P/S pump and A/C compressor pulleys
- Improper CKP Sensor mounting
- Poor connector/terminal to component connection. i.e., CKP Sensor, Fuel Injector, Ignition coil, etc.
- Vacuum leaks
- Restricted Air Intake system
Were any of the above conditions present?
Yes
- Repair as necessary.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test
No
- The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.