Code
P1231
DAEWOO
P — Powertrain
FUEL PUMP RELAY FLT(PWR SHT)
AI status
Completed
Completed
100%
Causes
- Failed or sticking fuel pump relay
- Blown fuse for fuel pump circuit
- Open, shorted or intermittent wiring between relay, pump, and PCM/ECM
- Poor ground at fuel pump or relay
- High current draw from a failing fuel pump causing protection to trip
- Faulty ECM/PCM driver for the relay circuit
Symptoms
- No start or intermittent no-start
- Engine stalls or dies while driving
- Fuel pump does not run or runs intermittently
- Check Engine Light (MIL) illuminated with P1231 stored
- Possible poor fuel pressure or hard starting
What to check
- Scan for stored codes and freeze-frame data; note conditions when code set
- Visually inspect fuel pump relay, fuse(s), relay socket and related connectors for corrosion or damage
- Listen for fuel pump operation when ignition is cycled and when cranking
- Swap relay with identical known-good relay (if available) to rule out relay defect
- Measure battery voltage at relay feed and at fuel pump connector while cranking and while running
- Check continuity and resistance of relay coil and relay contacts in socket
Signal parameters
- Battery feed to pump relay: ~12 V (engine off, battery healthy), ≥10 V during cranking
- Relay coil resistance (typical automotive 12 V relay): ~50–200 Ω (varies by relay)
- Fuel pump supply voltage at pump connector when running: ~11–13.5 V
- Fuel pump current draw (typical in-tank pump): ~4–15 A depending on vehicle and pump; large deviation indicates fault
- Control signal from ECM to relay: either battery voltage or switched ground depending on design — should change state when key ON/crank
Diagnostic algorithm
- Verify the code with a scan tool and record freeze-frame; clear codes and attempt to re-create the fault under the same conditions.
- Inspect fuses and fusible links for the fuel pump circuit; replace if blown and retest.
- Inspect relay and socket for corrosion or heat damage; swap with identical relay to test function.
- Probe relay socket: confirm constant battery feed present and that the ECM control terminal changes state (ground or +12 V) when pump should run (key ON/crank).
- Measure voltage at fuel pump connector while cranking/running. If voltage is absent or drops to zero when code appears, trace wiring back to relay and ECM for opens/shorts.
- Check ground continuity for pump and relay; repair any high-resistance grounds.
- Measure pump current draw. If current is abnormally high, replace pump and inspect fuel inlet/filter. If current is normal and voltage is switched off, suspect relay or ECM driver.
- If wiring, relay, fuse and pump check OK, test/replace ECM or investigate immobilizer/security cut-off as per manufacturer procedures.
- After repairs, clear codes and perform road/crank test to confirm problem is resolved and code does not return.
Likely causes
- Corroded/loose relay socket or connector
- Blown fuse or fusible link in pump feed
- Relay contact failure (stuck open or intermittent)
- Damaged wiring harness or connector to in-tank pump
- Excessive pump current draw due to pump fault or restricted inlet
Fault status
Status
Fuel pump relay power shut detected — ECM observed loss or interruption of supply to the fuel pump relay when it should be powered. Circuit interruption, relay failure, wiring or control driver fault possible.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Repair manuals
Manual library for DAEWOO
75
Browse 75 DAEWOO manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
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- CDX, 4D Wagon, Standard
- SX, 4D Hatchback, Automatic
- SX, 4D Hatchback, Standard
- SX, 4D Sedan, Automatic
- SX, 4D Sedan, Standard
- SX, 4D Wagon, Automatic
- SX, 4D Wagon, Standard
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