OBD-II Fault Codes

Introduction The P0102 diagnostic trouble code indicates that the Mass Air Flow (MAF) sensor signal voltage sent to the powertrain control module (PCM) is lower than expected. The MAF sensor measures the volume and density of air entering the engine so the computer can calculate the correct amount of fuel. When the MAF signal voltage […]

Introduction The P0442 diagnostic trouble code indicates that the powertrain control module (PCM) has detected a minor leak in the Evaporative Emission Control (EVAP) system. Unlike a major leak code (P0455), code P0442 refers to a very small vapor leak—typically a hole or gap smaller than 0.04 inches in diameter. The EVAP system traps fuel

Introduction The P0120 diagnostic trouble code indicates a general circuit failure in the Throttle Position Sensor (TPS) “A” or Pedal Position Sensor circuit. The TPS measures how far the throttle plate is open and feeds this data directly to the powertrain control module (PCM) to control fuel delivery and ignition timing. If the PCM receives

Introduction The P0325 diagnostic trouble code indicates a malfunction in the circuit of Knock Sensor 1 on Bank 1. The knock sensor functions like a small microphone, detecting internal engine vibrations caused by premature detonation or “knocking.” The powertrain control module (PCM) uses this data to retard ignition timing and protect the engine. When the

Introduction The P0422 diagnostic trouble code indicates that the efficiency of the main catalytic converter on Bank 1 has dropped below the minimum acceptable factory threshold. The powertrain control module (PCM) compares readings from the upstream and downstream oxygen sensors. When both sensors report similar oxygen fluctuation patterns, it signals that the catalyst is no

Introduction The P0113 diagnostic trouble code indicates that the powertrain control module (PCM) has detected a high voltage signal from the Intake Air Temperature (IAT) sensor. The IAT sensor measures the temperature of the air entering the engine, allowing the computer to adjust fuel injection timing based on air density. A “high input” signal means

Introduction The P0455 diagnostic trouble code indicates a major leak has been detected in the Evaporative Emission Control (EVAP) system. The EVAP system is a sealed network designed to trap fuel vapors from the gas tank and route them into the engine to be burned, preventing them from escaping into the atmosphere. A large leak

Introduction The P0174 diagnostic trouble code indicates that the air-fuel mixture is running too lean in Bank 2 of the engine (the cylinder bank that does not contain cylinder #1). The powertrain control module (PCM) detects too much oxygen or insufficient fuel in the exhaust gases. If left uncorrected, a prolonged lean condition can cause

Introduction The P0141 diagnostic trouble code indicates a malfunction in the heater circuit of the downstream oxygen sensor (Bank 1, Sensor 2). This sensor is located after the catalytic converter and is primarily used to monitor catalyst efficiency. Like the upstream sensor, it features an internal heater to bring it to operating temperature quickly. When

Introduction The P0130 diagnostic trouble code indicates a failure in the circuit of the upstream oxygen sensor located on Bank 1 (Sensor 1). The powertrain control module (PCM) relies on this sensor to monitor the oxygen content in the exhaust gases immediately after leaving the engine. This real-time data is critical for adjusting the air-fuel