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

• P1851 — P1851 — Transfer Unit Contact Plate B Circuit Malfunction. P1851 often leaves the vehicle drivable in two-wheel drive, but four-wheel drive may be disabled or unreliable.
• P1852 — P1852 — Transfer Unit Contact Plate B Circuit Fault. P1852 can prevent the transfer unit from selecting the requested drive or low range.
• P1853 — P1853 — Transfer Unit Contact Plate B Ground Short. P1853 can prevent the transfer unit from changing drive modes or cause inconsistent mode selection.
• P1854 — P1854 — Transfer Unit Contact Plate C Circuit. P1854 can prevent 4WD/AWD engagement or leave the transfer unit in the wrong mode.
• P1855 — P1855 — Transfer Unit Contact Plate C Circuit Fault. P1855 can prevent the transfer unit from completing a mode change or confirming its operating state.
• P1856 — P1856 — Transfer Case C Plate Short to Positive. P1856 can interrupt four-wheel-drive mode selection and, if sustained, damage wiring or a connector.
• P1857 — P1857 — Transfer Unit Contact Plate C Ground Short. P1857 indicates a ground short in the transfer unit contact plate C circuit, so four-wheel-drive or terrain modes may not engage correctly.
• P1858 — P1858 — Transfer Unit Contact Plate D Circuit Malfunction. P1858 can leave the transfer unit without the requested drive mode and may affect traction.
• P1859 — P1859 — Transfer Unit Contact Plate D Circuit Fault. If the vehicle remains in its normal two-wheel-drive mode and P1859 causes no unusual noise or shifting, it may be driven cautiously to a repair shop.
• P1860 — P1860 — Transfer Case D Plate Short to Positive Supply. P1860 can prevent four-wheel-drive or other transfer case modes from operating correctly and may allow continued electrical damage if the short remains.
• P1861 — P1861 — Transfer Unit Contact Plate D Short to Ground. Driving may be possible, but four-wheel-drive engagement can be unavailable or unreliable.
• P1862 — P1862 — Transfer Case Contact Plate Power Supply Fault. Driving in 2WD may be possible if the transfer case is fully disengaged, but P1862 can leave 4WD or low range unavailable or incorrectly indicated.
• P1864 — P1864 — Transfer Case Contact Plate Power Short. P1864 can prevent the transfer case from changing modes as commanded.
• P1865 — P1865 — Transfer Unit Contact Plate Supply Short to Ground. P1865 can prevent proper transfer-unit engagement while the vehicle may still drive in a default mode.
• P1866 — P1866 — Transfer Case Control Circuit Fault. P1866 can prevent the transfer case from reaching the selected drive mode.
• P1867 — Transmission Transfer Case Contact Plate Power Circuit Failure (P1867): 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), low or degraded transmission fluid, faulty transmission speed sensor.
• P1868 — Transmission Transfer Case Contact Plate Power Open Circuit (P1868): 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), low or degraded transmission fluid, wiring or connector faults in the valve body harness.
• P1869 — P1869 — Transmission Transfer Case Contact Plate Power Short To Battery. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: internal mechanical wear (clutches, torque converter), faulty transmission speed sensor, valve body wear.
• P1870 — P1870 — Transmission Transfer Case Contact Plate Power Short To Ground. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: wiring or connector faults in the valve body harness, low or degraded transmission fluid, failed shift or pressure control solenoid.
• P1871 — OBD2 code P1871 flags a problem with the automatic transmission control (transmission transfer case system concern - servicing required). Short, gentle driving to a shop is usually possible. Common culprits: wiring or connector faults in the valve body harness, valve body wear, low or degraded transmission fluid.
• P1872 — Transmission Transfer Case Contact Plate General Circuit Failure (P1872): 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.
• P1873 — OBD2 code P1873 flags a problem with the automatic transmission control (transmission automatic 4-wheel drive indicator (Lamp) circuit failure). Short, gentle driving to a shop is usually possible. Common culprits: valve body wear, faulty transmission speed sensor, failed shift or pressure control solenoid.
• P1874 — P1874 — Transmission Automatic 4-Wheel Drive Indicator (Lamp) Circuit Short To Battery. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: low or degraded transmission fluid, valve body wear, internal mechanical wear (clutches, torque converter).
• P1875 — P1875 — Transmission Component Slipping/ Transmission Mechanical Transfer Case 4x4 Switch Circuit Failure. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: failed shift or pressure control solenoid, faulty transmission speed sensor, wiring or connector faults in the valve body harness.