OBD-II Code
P1431
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$80–$950
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P1431 indicates the secondary fuel level sensor (Sensor 2, located in the secondary saddle of a two-sided saddle-tank, or on the passive side of a siphon-fed dual-pump setup) is reporting a value outside the rational range — typically the sensor's resistance is reading outside 40-250 ohms across the float sweep, or its rate of change disagrees with Sensor 1 by more than a calibrated delta over a fuel-level transition.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP1431 indicates the secondary fuel level sensor (Sensor 2, located in the secondary saddle of a two-sided saddle-tank, or on the passive side of a si…
P1431 indicates the secondary fuel level sensor (Sensor 2, located in the secondary saddle of a two-sided saddle-tank, or on the passive side of a siphon-fed dual-pump setup) is reporting a value outside the rational range — typically the sensor's resistance is reading outside 40-250 ohms across the float sweep, or its rate of change disagrees with Sensor 1 by more than a calibrated delta over a fuel-level transition.
Diagnose cheapest first
- scan-tool both fuel level sensors and watch the raw voltage/percentage as the tank drains across a full driving cycle — the two should track within 10% of each other on a saddle-tank truck once fuel sloshes equalize.
- If Sensor 2 reads pinned at 0% or 100% while Sensor 1 sweeps normally, the secondary sender's float arm has separated from the rheostat (a documented saddle-tank failure) or the wiring to the secondary sender has rubbed through at the frame-rail clip.
- The expensive misdiagnosis: dropping the fuel tank ($600+ labor on a long-bed) when the actual fault is a $12 connector full of corroded brass — always pin-test the harness first.
Vehicle-specific patterns1999-2006 Silverado/Sierra 4.8L/5.3L/6.0L extended/crew cab with the side-saddle dual-tank or single-tank-dual-sender configuration is the canonical…
- 1999-2006Silverado/Sierra 4.8L/5.3L/6.0L extended/crew cab with the side-saddle dual-tank or single-tank-dual-sender configuration is the canonical P1431 vehicle — the secondary sender's plastic float arm cracks at the pivot and floats off the rheostat (TSB 03-06-04-007 covers the redesigned float assembly).
- 2007-2013Silverado/Sierra 5.3L sees P1431 from the siphon-jet pump assembly failing on the secondary side, which the PCM detects via the disagreeing sensor readings.
- 2003-2009Hummer H2 6.0L gets P1431 from the same saddle-tank float failure.
- 2005-2009Trailblazer EXT/Envoy XL with the larger fuel tank throws P1431 from a chafed sender harness at the body-mount crossmember.
Estimated repair$80 to $950.
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