Misfire Detection Monitor – Cylinder 1 Misfire
Description:
How does a P0301 code trigger the check engine light? This code will trigger the check engine light as follows:
The misfire detection monitor, a software strategy built into the computer, is designed to detect an engine misfire. The computer can also normally identify the specific cylinder in which the misfire has occurred. A misfire is nothing more than a lack of combustion, which can be caused by poor fuel quality or metering, low compression, lack of spark or unmetered air entering the engine. There are other possible, less obvious causes as well, such as uncommanded Exhaust Gas Recirculatin (EGR), flow. When the misfire monitor detects a misfire, it will trigger the check engine light with the specific cylinder number as the last digit in the P030X code. For instance cylinder 1 misfire is P0301, cylinder 2 is P0302 etc.
Possible Causes:
Fuel injectors, related wiring, sensors and computer issues
Running out of gas, or poor fuel quality
Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine
Incorrect Fuel Pressure
EGR system concerns: leaking EGR valve or restricted ports
Base engine concerns: low compression, valve train problems and timing issues
Ignition system concerns including, but not limited to:
Faulty spark plugs
Faulty coil or related wiring
Ignition module or related wiring issues
Ignition related sensor faults or wiring issues
Diagnostic Help:
Begin by checking for proper fuel and ignition system operation, and then follow up with the less likely causes listed above, such as EGR and EVAP system problems. New style coil on plug applications have a high failure rate, and can be concluded faulty by swapping to another cylinder and checking to see if the misfire moves to that cylinder. This is a quick check if a capable scan tool or oscilloscope is not available. Always make sure the basic maintenance is done first and that things such as the fuel filter, air filter, spark plugs and spark plug wires are in good working order, as these are all possible candidates for a problem. If necessary, check for wiring and component concerns. See our article “Automotive Circuit Testing 101”, if you need more assistance with this. If concern is determined to be intermittent, check out our article on intermittent diagnosis and wiggle test connectors and wiring, attempting to duplicate concern. You may also use the “Get Help” link if you need specifications or have any other related questions. Remember to refer to an appropriate manual for specific instruction.
System Too Lean – Bank 1
Description:
How does a P0171 code trigger the check engine light? This code will trigger the check engine light as follows:
The adaptive fuel strategy in the vehicle’s computer constantly monitors the fuel delivery system to make sure the engine is running at an optimum air to fuel ratio, which is 14.7:1. The computer adjusts injector pulse width to regulate the amount of fuel going into the engine. The oxygen sensors relay information to the Powertrain Control Module (computer), informing it of the oxygen content in the exhaust. This information is translated by the computer, and used to determine if more or less fuel is needed. The computer will then adjust fuel flow (and possibly other related engine operating characteristics), to keep the correct air fuel mixture. This loop continues as long as the engine is running. Please refer to our article Oxygen Sensor Code Diagnosis for more info on this system. A P0171 check engine light code is set when the computer has reached a rich calibration limit and can not add enough fuel to maintain the correct mixture.
Possible Causes:
Refer to our Oxygen Sensor Code Diagnosis article for a list of all possible causes. The following is an overview of P0171 check engine light code possible causes.
Fuel System:
Leaking or faulty fuel pressure regulator
Plugged or dirty fuel filter or lines
Fuel pump weak or defective check valve
Injectors leaking or faulty
Low fuel pressure or running out of fuel
Leaking EVAP system components
Faulty FRP (Fuel Rail Pressure Sensor)
Air Intake System
Vacuum leaks
Contaminated, damaged or faulty Mass Air Flow sensor
PCV valve leak or stuck open
Air induction turbulance caused by wrong filter
Oil dipstick not seated
Air leaks after the Mass Air Flow Sensor (MAF)
Oil coated aftermarket air filter
Exhaust System
Any exhaust leak before or near the oxygen sensors
EGR System
Vacuum line disconnected from EGR System Module (ESM)
EGR valve, tube or gasket leak
EGR vacuum regulator valve leaking
Secondary Air Injection System
Mechanically stuck secondary air injection valve
Intake Cam Position Timing Over Retarded – Bank 2
Description:
How does a P0022 code trigger the check engine light? This code will trigger the check engine light under the following condition:
The comprehensive component monitor, referred to as the CCM, monitors the Variable Camshaft Timing (VCT) position for over-retarded cam timing. If the cam timing exceeds a maximum calibrated limit or is stuck in a retarded position, the check engine light will come on and set this trouble code.
Possible Causes:
Incorrect camshaft timing
VCT solenoid valve stuck open or continuous oil flow to piston chamber
Camshaft advance mechanism binding, or faulty VCT unit
Diagnostic Help:
This check engine light code is caused by a mechanical fault of the VCT unit or related components, so there is no need for electrical diagnosis. Possible symptoms may include rough idle, stall or hard start. Refer to manufacturer specific component tests for the VCT unit. You may also use the “Get Help” link if you need specifications or have any other related questions. Remember to refer to an appropriate manual for specific instructions.
Intake Cam Position Timing Over Advanced – Bank 2
Description:
How does a P0021 code trigger the check engine light? This code will trigger the check engine light under the following condition:
The comprehensive component monitor, referred to as the CCM, monitors the Variable Camshaft Timing (VCT) position for over-advanced cam timing. If the cam timing exceeds a maximum calibrated limit or is stuck in an advanced position, the check engine light will come on and set this trouble code.
Possible Causes:
Incorrect camshaft timing
VCT solenoid valve stuck open or continuous oil flow to piston chamber
Camshaft advance mechanism binding, or faulty VCT unit
Diagnostic Help:
This check engine light code is caused by a mechanical fault of the VCT unit or related components, so there is no need for electrical diagnosis. Possible symptoms may include rough idle, stall or hard start. Refer to manufacturer specific component tests for the VCT unit. You may also use the “Get Help” link if you need specifications or have any other related questions. Remember to refer to an appropriate manual for specific instructions.
Intake Cam Position Actuator Open Circuit – Bank 2
Description:
How does a P0020 code trigger the check engine light? This code will trigger the check engine light under the following condition:
The comprehensive component monitor, referred to as the CCM, monitors the Variable Camshaft Timing (VCT) circuit to the computer for high and low voltages. If the voltage falls below a set limit for a specific amount of time during this test, the check engine light will come on and set this trouble code.
Possible Causes:
Open or short in the VCT circuit
Open in the Vehicle Power circuit
Open or short in the VCT solenoid valve itself
Damaged computer (PCM)
Diagnostic Help:
This check engine light code is caused by a circuit fault of the VCT system. Testing should include all related wiring circuits, the VCT solenoid and PCM itself. Please refer to out article on Automotive Circuit Testing for help with this. You may also use the “Get Help” link if you need specifications or have any other related questions. Remember to refer to an appropriate manual for specific instructions.
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