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Home / DTC / B1991 — Front / rear pedal potentiometer feedback circuit - short circuit to the battery

B1991 — Front / rear pedal potentiometer feedback circuit - short circuit to the battery

Detailed page for trouble code B1991.

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B1991

LAND ROVER B — Body

Front / rear pedal potentiometer feedback circuit - short circuit to the battery

Brand: LAND ROVER
Type: B — Body
Views: UK: 5 EN: 8 RU: 3
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Page language: EN

Causes

  • Damaged wiring harness with chafing or insulation breach contacting battery voltage
  • Corroded or pushed-back connector pins causing a short to battery supply
  • Internal short in the pedal potentiometer (accelerator/brake pedal position sensor)
  • Aftermarket device or improper repair creating a direct feed of battery voltage into the signal circuit
  • ECU input stage fault (internal short to battery at the module pin)
  • Water ingress or contamination at sensor/connector producing conductive path to battery voltage

Symptoms

  • Malfunction Indicator Lamp (MIL) / dash warning related to throttle or traction control
  • Loss of throttle response or reduced power (limp-home mode)
  • Pedal position readings stuck high or jump to battery voltage when monitored with scan tool
  • Cruise control disabled or intermittent operation
  • Stored DTC B1991 (and possibly related throttle/pedal codes)

What to check

  • Read and record freeze-frame and live data for pedal position sensors with a scan tool
  • Inspect pedal sensor and wiring harness visually for damage, pinched sections, heat or corrosion
  • Back-probe the pedal sensor connector and measure signal, supply (5V ref) and ground with ignition ON (engine OFF)
  • With connector disconnected, check for battery voltage on the signal lead (should NOT be battery voltage)
  • Perform continuity/resistance checks between signal wire and battery positive to confirm short, and between signal and ground to check for leakage
  • Wiggle-test wiring and connectors while monitoring live data to try to reproduce the fault

Signal parameters

  • Reference supply (Vref) to pedal sensor: ~5.0 V (key ON, engine OFF)
  • Signal output at rest (pedal released): typically ~0.5–1.0 V (varies by design)
  • Signal output at full pedal travel: typically ~4.0–4.5 V
  • End-to-end potentiometer resistance (typical range): ~5 kΩ–20 kΩ (manufacturer-specific)
  • Short-to-battery symptom: signal wire measures ~12 V or battery voltage on the signal pin with sensor connected or disconnected

Diagnostic algorithm

  1. Connect a diagnostic scan tool and record live pedal position sensor voltages and any related codes (note freeze-frame data)
  2. Visually inspect pedal sensor, harness, and connectors for damage, corrosion, water ingress or recent repair evidence
  3. Back-probe the pedal sensor connector: verify Vref (~5 V), signal voltage, and ground with ignition ON (engine OFF). Note if signal reads battery voltage (~12 V)
  4. Disconnect pedal sensor harness connector and measure voltage on the harness signal pin. If it still shows battery voltage, the short is in the wiring or ECU; if it goes away, suspect the pedal sensor
  5. Perform continuity/ohm tests: measure resistance between signal wire and battery positive to confirm short to battery; measure signal-to-ground for leakage
  6. Isolate sections of the harness: unplug intermediate connectors, check continuity and re-test until the short location is narrowed
  7. If wiring and connectors test OK, install a known-good pedal sensor (or bench test original) to confirm sensor failure before replacing ECU
  8. If tests point to ECU internal short, confirm wiring harness and connectors are good, then follow manufacturer procedure for ECU testing/replacement
  9. Repair damaged wiring, replace corroded connectors or the pedal sensor as required, clear codes and road test to verify repair

Likely causes

  • Chafed or pinched wiring near pedal or bulkhead contacting constant 12V circuit
  • Corroded connector at pedal or ECU causing pin-to-pin short to Vb
  • Failed pedal potentiometer with internal short to the supply rail
  • Damage from recent work in the footwell area (fastener, zip-tie, screw) piercing wiring harness

Fault status

⚠️ Status
Front/rear pedal position sensor feedback circuit is shorted to battery voltage. ECU detects an over-voltage on the pedal signal line; inspect pedal sensor, wiring and connectors for short to 12V.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

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B1990 B1992 P0122 P0123 P2138
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