Faulty fuel level sensor (sending unit) in the secondary tank, often due to wear or sulfur contamination on the resistor card; Damaged or corroded wiring harness or connector at the secondary tank sensor; Poor ground connection for the fuel level sensor circuit; Failed fuel tank pressure sensor or fuel pump module assembly that incorporates the level sensor; PCM calibration issue or faulty PCM (rare, but possible after other causes are ruled out); Contaminated fuel or debris causing the float to stick or move erratically; Aftermarket or incorrect fuel level sensor installed previously

DTC codes / GM codes / P1431

P1431 · GMFuel Level Sensor 2 Performance

Q: What does code P1431 mean?

Fuel Level Sensor 2 Performance. P1431 on GM vehicles means the powertrain control module (PCM) has detected a performance problem with the fuel level sensor in the secondary fuel tank, typically on dual-tank trucks and SUVs. The PCM compares the signal from this sensor against expected values and flags the code when the reading is erratic, stuck, or outside the plausible range for the fuel volume it calculates.

P1431 on GM vehicles means the powertrain control module (PCM) has detected a performance problem with the fuel level sensor in the secondary fuel tank, typically on dual-tank trucks and SUVs. The PCM compares the signal from this sensor against expected values and flags the code when the reading is erratic, stuck, or outside the plausible range for the fuel volume it calculates.

SystemPowertrain

Code typeGM specific

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Fuel gauge reads incorrectly or fluctuates, especially when switching between tanks
Fuel gauge may show empty or full when the tank is not actually at that level
Often no symptoms besides the warning light, with the gauge appearing normal to the driver
Incorrect fuel range or distance-to-empty calculations on the driver information center
Possible fuel transfer or tank switching issues on vehicles with dual tanks
Remote start or fuel system monitoring features may be disabled as a result of the code

Common causes, most likely first

Faulty fuel level sensor (sending unit) in the secondary tank, often due to wear or sulfur contamination on the resistor card
Damaged or corroded wiring harness or connector at the secondary tank sensor
Poor ground connection for the fuel level sensor circuit
Failed fuel tank pressure sensor or fuel pump module assembly that incorporates the level sensor
PCM calibration issue or faulty PCM (rare, but possible after other causes are ruled out)
Contaminated fuel or debris causing the float to stick or move erratically
Aftermarket or incorrect fuel level sensor installed previously

How to diagnose and fix it

Use a scan tool to read the fuel level sensor voltage or resistance values for both tanks and compare them while monitoring live data
Visually inspect the wiring and connector at the secondary fuel tank for chafing, corrosion, or loose pins
Check the ground circuit for the fuel level sensor with a multimeter to ensure less than 0.1 volt drop
Remove the secondary fuel level sensor and inspect the float, resistor card, and arm for binding or contamination
Test the sensor with a multimeter through its full range of motion to check for dead spots or erratic resistance
Replace the faulty fuel level sensor or fuel pump module assembly if testing confirms it is out of specification
Clear the code and verify the repair by test-driving while monitoring fuel level sensor data to ensure the code does not return

Why the fuel gauge lies before the code sets

The PCM often sets P1431 only after multiple drive cycles with inconsistent fuel level readings, so the gauge may have been inaccurate for weeks before the light appeared.
On GM dual-tank trucks, the secondary tank sensor signal is often affected by a poor ground at the frame rail, which can mimic a failed sensor and is frequently overlooked.
A fuel level sensor that reads correctly when stationary can still fail P1431 because the PCM checks for signal changes during fuel transfer and driving; a sticky float may only act up when fuel sloshes.
Replacing the fuel level sensor without checking the fuel tank pressure sensor or the wiring harness can lead to a repeat code if the real problem is a chafed wire inside the tank.
Some aftermarket fuel level sensors have resistance curves that do not match the GM calibration, causing P1431 to set even though the sensor is new and the gauge appears to work.

Can I keep driving with P1431?

You can generally continue driving with P1431 because it does not affect engine operation or safety, but do not rely on the fuel gauge for accurate fuel level, especially on dual-tank models. Refuel before the tank is truly empty and have the sensor diagnosed soon to avoid running out of fuel unexpectedly.

Tools that help

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Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.