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Home / DTC / B2871 — Pump motor:short to battery

B2871 — Pump motor:short to battery

Detailed page for trouble code B2871.

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Code

B2871

MITSUBISHI B — Body

Pump motor:short to battery

Brand: MITSUBISHI
Type: B — Body
Views: UK: 16 EN: 24 RU: 18
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Page language: EN

Causes

  • Damaged/abraded wiring contacting battery positive or a constant 12V source
  • Failed pump motor with internal short
  • Shorted pump driver or power transistor inside the control module
  • Corroded or bridged connector terminals (water ingress, debris)
  • Aftermarket equipment or recent repairs that disturbed harness routing or insulation
  • Blown or repeatedly failing fuse/relay associated with the pump circuit

Symptoms

  • DTC B2871 stored/Check Engine/Warning lamp illuminated
  • Associated pump not operating or operating intermittently
  • Blown fuse or repeated fuse failure on pump circuit
  • Parasitic battery drain or sudden battery discharge
  • Noise or seizure from the pump (if partially shorted)
  • Reduced system performance related to pump function (fuel, cooling, washer, depending on pump)

What to check

  • Read and record all stored codes and freeze-frame data with scan tool
  • Visually inspect pump wiring harness, connectors, and nearby routing for chafing, heat damage, corrosion, or pinching
  • Inspect related fuses and relays for evidence of melting or repeated failure
  • Unplug the pump connector and check for presence of battery voltage on the circuit with key ON (verify expected behavior)
  • Measure voltage at the pump connector while activated and when not activated
  • Measure resistance of the pump motor (with connector disconnected) and compare to specification

Signal parameters

  • Expected supply voltage to pump when ON: ~11.5–14.5 V (vehicle running/ignition ON as applicable)
  • Expected supply voltage to pump when OFF: 0 V at the switched output (no battery feed unless constant power circuit)
  • Pump motor DC resistance (typical range): ~0.1–5 Ω (varies by pump type) — consult service data
  • Expected pump current draw (typical): 2–20 A depending on pump; repeated fuse rating often 10–30 A — consult service data
  • Voltage at control/module output when shorted: may show battery voltage present continuously or excessive current causing voltage drop

Diagnostic algorithm

  1. Use a scan tool to read/record all DTCs and freeze-frame data. Note ignition state and any correlated events.
  2. Perform a visual inspection of pump, harness, connectors, fuses, and relays for damage, heat discoloration, corrosion, or aftermarket splices. Repair obvious damage before further testing.
  3. With ignition OFF, disconnect the pump connector. Inspect connector terminals for corrosion, melting or bridged pins.
  4. With connector disconnected, check for battery voltage present on the harness power feed with ignition OFF and ON as specified by service manual. A constant battery feed where a switched feed is expected indicates a short/incorrect wiring.
  5. Measure coil/motor resistance at the pump connector. Compare to service spec. Very low resistance suggests an internal short.
  6. If resistance is within spec, perform an in-circuit current draw test with the pump connected and activated (use clamp meter or inline ammeter). Excessive current indicates internal pump fault or short.
  7. Wiggle the harness and connectors while observing voltage/current and scan tool data to find intermittent shorts.
  8. Isolate the circuit by supplying known-good fused 12V to the pump (or bench-test the pump) to verify pump operation independent of vehicle wiring. If pump draws excessive current or is shorted, replace pump.
  9. If pump bench test is good and harness/isolation checks show battery short remains, suspect pump driver or control module. Test module output and driver components per factory procedures; replace module or repair driver only after verification.
  10. After repairs, restore connectors, replace any damaged fuses/relays, clear codes, and perform functional test and road test to confirm fault does not return.

Likely causes

  • Chafed harness where it rubs on body or frame, contacting battery positive wiring
  • Pump motor windings internally shorted to the motor case
  • Connector pin melted/bridged causing positive feed to be present when it should be switched
  • Faulty pump driver MOSFET/transistor in the ECU/pump module shorted to battery
  • Incorrect repairs or installation (incorrect splice to constant 12V)

Fault status

⚠️ Status
High-side (battery positive) short detected in pump motor circuit. Circuit overcurrent or unintended battery feed present; pump operation may be disabled.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours

Similar codes

B2870 B2872 P0620 P0627 P0563
203

Browse 203 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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