Powertrain, generic · Fuel and air metering (injector circuit)

P0231 Fuel Pump Secondary Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The fuel pump circuit has two sides: the primary circuit is the engine module's output to the fuel pump relay coil (or to a pump control module), the secondary circuit is the power circuit from relay contact or module to the pump itself. P0231 means the secondary side reads low, and the meaning differs by system. Ford's relay systems read the voltage in the pump power circuit through a monitor wire: if it is missing with the pump commanded on – relay contact not closing, fuse missing, wire open or shorted to ground – the code sets after 2–5 s. GM pumps with their own power module report a short to ground as overcurrent at 18 A or more, setting the warning light in the first trip and switching the output off. The pump gets no voltage, so the engine will not start or stalls.

Likely causes

Power wire from relay or module to pump shorted to ground (chafing at tank or underbody)
Relay contact not closing, fuse or battery feed to the relay missing
Pump motor jammed or shorted (high current)
Connector at the tank flange corroded or burnt
Pump control module faulty

Symptoms

  • Engine cranks but does not start
  • Engine stalls while driving
  • Check engine light on
  • Blown fuel pump fuse

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–800
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel pumpfuel pump relayfuel pump control modulefuel pump wiring

Related codes

P0230P0232P0233P023FP2635P0628

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, saabwisonline.com.