Powertrain
Manufacturer-specific
OBD-II Fault Code
P1231: Fuel Pump Secondary Circuit Low, High Speed
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P1231.
Fuel system
Use this category to narrow your checks before replacing parts.
High
Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.
What P1231 usually means
Fuel Pump Secondary Circuit Low, High Speed.
Common symptoms
Check Engine light; Poor drivability or reduced fuel economy depending on fault; Hard start, hesitation, stalling or inaccurate fuel reading depending on component
Likely causes
Low fuel pressure; Faulty pump/regulator/sensor; Wiring fault; Clogged filter; Injector fault; Low signal voltage; Weak power supply; High resistance/poor ground; Failed sensor; High signal voltage; Open ground; Short to voltage
Diagnostic checks
Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Check fuel pressure and sensor data; Inspect pump/injector fuses, relay, wiring and grounds; Check sensor reference voltage, ground and signal voltage; Check sensor ground and signal circuit for short to voltage
Repair guidance
Repair wiring/relay issues, replace clogged filter, failed pump/sensor/injector only after testing; Repair poor ground/power feed or replace confirmed faulty sensor; Repair ground/signal circuit or replace confirmed faulty sensor
Verification after repair
Clear code, road-test through the same drive condition, then rescan