The P1625 code on your 2021 GMC Terrain indicates a problem with the fuel level sensor 2 circuit. This GM-specific code affects your Terrain's 1.5L or 2.0L turbocharged engine's fuel monitoring system. Vehicles with saddle-type fuel tanks often use two fuel level sensors, and this code specifically relates to the secondary sensor.
Understanding P1625 on Terrain
Some vehicles use dual fuel level sensors to accurately measure fuel in irregularly shaped or saddle-type fuel tanks. Sensor 2 typically monitors the secondary section of the tank. Code P1625 sets when the PCM detects an electrical fault in the sensor 2 circuit, including open circuits, short circuits, or erratic signal readings.
Common Symptoms
- Check engine light on
- Inaccurate fuel gauge readings
- Fuel gauge stuck at partial reading
- Distance-to-empty calculation errors
- Low fuel warning malfunction
- Fuel gauge may show partially full when empty
Primary Causes
- Faulty fuel level sensor 2
- Open circuit in sensor wiring
- Corroded connector at fuel tank
- Ground circuit problem
- Damaged wiring from road debris
- Fuel tank contamination affecting sensor
- Float mechanism stuck or damaged
Diagnostic Procedure for 2021 Terrain
Start by monitoring fuel level sensor 2 readings with a scan tool - compare to sensor 1 readings for consistency. Test sensor circuit voltage at the fuel tank connector. Check wiring continuity from connector to PCM. Inspect connector for corrosion or damage. If possible, observe sensor float movement when tank is at different levels. Ground circuit testing is critical as both sensors often share a common ground.
Repair Solutions
Clean corroded connectors with electrical contact cleaner and apply dielectric grease. Repair any damaged wiring found during inspection. If the fuel level sensor 2 is faulty, replacement requires fuel tank access - the sensor may be integrated with the fuel pump module or mounted separately depending on design. After replacement, clear codes and verify accurate fuel gauge readings across various fill levels.