P0420 Code: Catalyst System Efficiency Below Threshold (Bank 1) Diagnostic
OBD2 code P0420 indicates that the Bank 1 catalytic converter's oxygen storage capacity has dropped below the minimum emissions threshold. The downstream O2 sensor is mirroring upstream sensor switching.
P0171 Code: System Too Lean (Bank 1) Causes, Smoke Test & Fix
OBD2 code P0171 indicates that the engine computer has reached its maximum fuel enrichment limit (+20% to +25% fuel trim) trying to compensate for an air-fuel mixture that contains excess unmetered air.
P0300 Code: Random / Multiple Cylinder Misfire Diagnostic Guide
OBD2 code P0300 indicates that the engine control module has detected random, intermittent misfires occurring across multiple cylinders simultaneously rather than isolated to a single cylinder.
P0700 Code: Transmission Control System Malfunction Diagnostic Guide
OBD2 code P0700 is an informational DTC indicating that the Transmission Control Module has illuminated the Check Engine Light and stored internal transmission codes.
P0335 Code: Crankshaft Position Sensor (CKP) Circuit Malfunction Fix
OBD2 code P0335 indicates that the engine control module has lost the reference timing signal from the Crankshaft Position Sensor, preventing spark and injection.
P0101 Code: Mass Air Flow (MAF) Sensor Circuit Range/Performance Fix
OBD2 code P0101 indicates that the Mass Air Flow sensor signal is irrational compared to calculated airflow from engine RPM, throttle position, and manifold pressure.
P0442 Code: EVAP System Small Leak Detected Diagnostic & Smoke Test
OBD2 code P0442 indicates that the EVAP monitor detected a small fuel vapor leak (equivalent to a 0.040-inch pinhole) during pressure decay testing.
P0304 Code: Cylinder 4 Misfire Detected Causes, Swap Test & Fix
OBD2 code P0304 indicates that the engine computer has detected incomplete combustion specifically isolated to Cylinder 4.
P0303 Code: Cylinder 3 Misfire Detected Diagnostic & Repair Guide
OBD2 code P0303 indicates that the engine control module has recorded consistent combustion failures specifically on Cylinder 3.
P0302 Code: Cylinder 2 Misfire Detected Causes & Coil Swap Test
OBD2 code P0302 indicates that the engine control module detected rotational crankshaft deceleration specifically during Cylinder 2 combustion power strokes.
P0430 Code: Catalyst System Efficiency Below Threshold (Bank 2) Fix
OBD2 code P0430 indicates that the Bank 2 catalytic converter has degraded below minimum emissions storage thresholds, mirroring Bank 1 code P0420.
P0340 Code: Camshaft Position Sensor (Bank 1) Circuit Malfunction Fix
OBD2 code P0340 indicates that the PCM has not detected the required square-wave pulse signal from the Bank 1 Camshaft Position Sensor during engine cranking.
P0113 Code: Intake Air Temp (IAT) Sensor Circuit High Input Diagnostic
OBD2 code P0113 indicates that the PCM detected maximum signal voltage (typically 5.0V) on the IAT sensor circuit, interpreting it as an open circuit or -40°F air.
P0507 Code: Idle Control System RPM Higher Than Expected Fix
OBD2 code P0507 indicates that the engine idle speed is higher than commanded by the engine computer (typically idling at 1,000+ RPM instead of 650-750 RPM).
P0301 Code: Cylinder 1 Misfire Detected Diagnostic & Swap Test
OBD2 code P0301 indicates that the crankshaft position sensor detected rotational deceleration specifically isolated to Cylinder 1 combustion events.
P0174 Code: System Too Lean (Bank 2) Diagnostic & Smoke Test Guide
OBD2 code P0174 indicates that the engine computer has reached its fuel enrichment limit (+20% or higher) trying to compensate for excess unmetered air on Bank 2.
P0401 Code: EGR Flow Insufficient Detected Diagnostic & Carbon Cleaning
OBD2 code P0401 indicates that the EGR system failed to introduce sufficient inert exhaust gases into the intake manifold to lower combustion temps.
P0128 Code: Coolant Thermostat Stuck Open Diagnostic & Repair
OBD2 code P0128 indicates that the engine has failed to reach normal operating temperature (typically 175°F to 195°F) within a calculated time and mileage window.
P0455 Code: EVAP System Large Leak Detected Causes & Fix Guide
OBD2 code P0455 indicates that the EVAP monitor detected a major fuel vapor leak (diameter greater than 0.090 inches) during vacuum decay testing.