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Home / DTC / P1252 — Pedal Correlation PDS1 and LPDS High

P1252 — Pedal Correlation PDS1 and LPDS High

Detailed page for trouble code P1252.

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Code

P1252

MERCURY P — Powertrain

Pedal Correlation PDS1 and LPDS High

Brand: MERCURY
Type: P — Powertrain
AI status
Completed
ready
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Page language: EN

Causes

  • Faulty accelerator/pedal position sensor(s) (PDS1 or LPDS)
  • Damaged, corroded or disconnected wiring or connectors between pedal sensors and PCM
  • Poor sensor reference voltage or ground (intermittent or low 5V reference)
  • Water intrusion or contamination of pedal sensor or connector
  • Faulty PCM (less common)
  • Incorrect or failed pedal assembly (aftermarket or wrong part)

Symptoms

  • Check Engine Light (MIL) illuminated
  • Reduced engine power / limp-home mode
  • Unresponsive, delayed, or unpredictable throttle response
  • Engine hesitation or poor acceleration
  • Possible stored or intermittent related throttle/pedal codes

What to check

  • Read freeze frame and full DTC list; note any related throttle/pedal codes
  • Use a scan tool to view live data: PDS1 and LPDS sensor voltages or percent values
  • Verify battery voltage stable while testing (low battery can affect readings)
  • Visually inspect pedal sensor connectors and harness for damage, corrosion, or water
  • Perform wiggle test of harness while watching live sensor data for intermittency
  • Check for proper reference voltage (typically ~5V) and good ground at sensor connector

Signal parameters

  • Sensor reference (VREF): approximately 5.0 V (check vehicle spec)
  • Sensor output range: typically ~0.5 V (rest) to ~4.5 V (full pedal) — vehicle-specific
  • PDS1 and LPDS should vary together with pedal travel and remain within a small offset (usually
  • PCM flags code when difference between PDS1 and LPDS exceeds manufacturer correlation limit or if one sensor is out-of-range

Diagnostic algorithm

  1. Connect a capable scan tool. Record freeze frame data and note any other stored codes.
  2. Clear codes. Operate the vehicle and recheck for immediate return to confirm repeat condition.
  3. With ignition ON (engine off) or per manufacturer instructions, monitor live data for PDS1 and LPDS. Slowly depress and release the pedal while observing both signals — they must track smoothly together.
  4. Check sensor connector pins for corrosion, bent pins, or moisture. Repair or dry as needed.
  5. Verify VREF (~5V) and ground at the sensor connector using a DVOM. Repair any wiring issues.
  6. Backprobe sensor signal wires and measure voltage while operating the pedal. Look for stuck, noisy, or out-of-range values, and for jumps during wiggle test.
  7. If wiring and connectors test good but one sensor output is inconsistent, replace the failed pedal position sensor or the pedal/module assembly (if sensors are integrated).
  8. If replacing sensors does not clear the issue, inspect/repair PCM connector and wiring to PCM. As a last resort consider PCM testing or replacement following manufacturer procedures.
  9. After repairs, clear codes and verify proper operation over a road test and re-check for DTC recurrence.

Likely causes

  • Open or short in signal wire from PDS1 or LPDS (short to voltage or ground)
  • Intermittent connector pin contact (corrosion bent pin)
  • Internal failure of one pedal position sensor producing out-of-range voltage
  • Damaged sensor harness at the pedal where it flexes
  • Integrated pedal module failure (sensors built into pedal assembly)

Fault status

⚠️ Status
PCM detected a high correlation difference between Pedal Position Sensor 1 (PDS1) and the low/secondary pedal position sensor (LPDS). Sensor signals are not tracking within expected limits; DTC P1252 set.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

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296

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