OBD2 Fault Code Library

Free lookup for thousands of OBD2 trouble codes: filter by family, read short meanings, and open deeper articles. Desktop ELM327 scanner with live data and AI guidance.

OBD2 symptoms

Look up diagnostic trouble codes by what the car is doing: misfire, overheating, rough idle, a check engine light, and other common symptoms.

• Engine misfire
• Engine overheating
• Rough idle
• Check engine light
• Poor fuel economy
• Hard starting
• Engine stalling
• Catalytic converter efficiency
• Oxygen sensor fault
• EVAP leak
• Thermostat not reaching temperature
• Lean air-fuel mixture
• Rich air-fuel mixture
• EGR flow fault
• Engine knock
• Charging system
• Throttle position
• Mass airflow sensor
• Turbo underboost
• Coolant temperature sensor
• Transmission fault

• P0858 — Traction Control Input Signal Low (P0858): a powertrain (engine/transmission) fault affecting the ABS / stability control. Short, gentle driving to a shop is usually possible. Most often caused by damaged tone (reluctor) ring on the hub, blown fuse or low voltage to the ABS module, failed wheel speed sensor.
• P0859 — Traction Control Input Signal High (P0859): a powertrain (engine/transmission) fault affecting the ABS / stability control. Short, gentle driving to a shop is usually possible. Most often caused by blown fuse or low voltage to the ABS module, damaged sensor wiring or corroded connector, failed wheel speed sensor.
• P085A — OBD2 code P085A flags a problem with the automatic transmission control (gear shift control module "B" communication circuit). Short, gentle driving to a shop is usually possible. Common culprits: internal mechanical wear (clutches, torque converter), low or degraded transmission fluid, valve body wear.
• P085B — Gear Shift Control Module "B" Communication Circuit Low (P085B): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by low or degraded transmission fluid, valve body wear, failed shift or pressure control solenoid.
• P085C — P085C — Gear Shift Control Module "B" Communication Circuit High. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: failed shift or pressure control solenoid, wiring or connector faults in the valve body harness, internal mechanical wear (clutches, torque converter).
• P085D — OBD2 code P085D flags a problem with the automatic transmission control (gear shift control module "A" performance). Short, gentle driving to a shop is usually possible. Common culprits: faulty transmission speed sensor, failed shift or pressure control solenoid, valve body wear.
• P085E — Gear Shift Control Module "B" Performance (P085E): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by internal mechanical wear (clutches, torque converter), faulty transmission speed sensor, low or degraded transmission fluid.
• P0860 — Gear Shift Module Communication Circuit (P0860): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by faulty transmission speed sensor, valve body wear, wiring or connector faults in the valve body harness.
• P0861 — P0861 — Gear Shift Module Communication Circuit Low. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: faulty transmission speed sensor, internal mechanical wear (clutches, torque converter), low or degraded transmission fluid.
• P0862 — P0862 — Gear Shift Module Communication Circuit High. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: faulty transmission speed sensor, internal mechanical wear (clutches, torque converter), low or degraded transmission fluid.
• P0863 — P0863 — TCM Communication Circuit. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: corroded, loose or damaged connector, control module driver fault, blown fuse feeding the circuit.
• P0864 — OBD2 code P0864 flags a problem with the sensor and actuator circuits (TCM communication circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit.
• P0865 — P0865 — TCM Communication Circuit Low. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, open or shorted wiring in the circuit, faulty sensor or actuator of the affected circuit.
• P0866 — TCM Communication Circuit High (P0866): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by control module driver fault, blown fuse feeding the circuit, open or shorted wiring in the circuit.
• P0867 — Transmission Fluid Pressure (P0867): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by wiring or connector faults in the valve body harness, valve body wear, internal mechanical wear (clutches, torque converter).
• P0868 — Transmission Fluid Pressure Low (P0868): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by wiring or connector faults in the valve body harness, internal mechanical wear (clutches, torque converter), failed shift or pressure control solenoid.
• P0869 — Transmission Fluid Pressure High (P0869): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by valve body wear, faulty transmission speed sensor, low or degraded transmission fluid.
• P0870 — Transmission Fluid Pressure Sensor/Switch "C" Circuit (P0870): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by internal mechanical wear (clutches, torque converter), valve body wear, wiring or connector faults in the valve body harness.
• P0871 — Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance (P0871): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by failed shift or pressure control solenoid, faulty transmission speed sensor, wiring or connector faults in the valve body harness.
• P0872 — Transmission Fluid Pressure Sensor/Switch "C" Circuit Low (P0872): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by internal mechanical wear (clutches, torque converter), faulty transmission speed sensor, wiring or connector faults in the valve body harness.
• P0873 — OBD2 code P0873 flags a problem with the automatic transmission control (transmission fluid pressure sensor/switch "C" circuit high). Short, gentle driving to a shop is usually possible. Common culprits: wiring or connector faults in the valve body harness, internal mechanical wear (clutches, torque converter), valve body wear.
• P0874 — OBD2 code P0874 flags a problem with the automatic transmission control (transmission fluid pressure sensor/switch "C" circuit intermittent). Short, gentle driving to a shop is usually possible. Common culprits: wiring or connector faults in the valve body harness, faulty transmission speed sensor, valve body wear.
• P0875 — OBD2 code P0875 flags a problem with the automatic transmission control (transmission fluid pressure sensor/switch "D" circuit). Short, gentle driving to a shop is usually possible. Common culprits: low or degraded transmission fluid, faulty transmission speed sensor, valve body wear.
• P0876 — OBD2 code P0876 flags a problem with the automatic transmission control (transmission fluid pressure sensor/switch "D" circuit range/performance). Short, gentle driving to a shop is usually possible. Common culprits: low or degraded transmission fluid, valve body wear, faulty transmission speed sensor.