Contaminated or worn accelerator pedal position sensor tracks inside the pedal assembly; Chafed, corroded, or loose wiring in the pedal sensor harness or connector; Poor electrical ground at the pedal sensor or PCM ground point; Failed accelerator pedal assembly (internal sensor drift or dead spot); PCM software calibration issue or internal PCM fault affecting signal processing; Voltage reference or signal return circuit fault shared by the two pedal sensors

DTC codes / Ford codes / P1256

P1256 · FordPedal Correlation PDS1 and HPDS

Q: What does code P1256 mean?

Pedal Correlation PDS1 and HPDS. P1256 on Ford vehicles indicates that the Powertrain Control Module (PCM) has detected a disagreement between the two independent accelerator pedal position signals, specifically the Pedal Demand Sensor 1 (PDS1) and the High-resolution Pedal Demand Sensor (HPDS). The PCM expects these two signals to track proportionally at all times, and when their correlation falls outside the calibrated tolerance, it stores this code and typically illuminates the wrench or check engine light.

P1256 on Ford vehicles indicates that the Powertrain Control Module (PCM) has detected a disagreement between the two independent accelerator pedal position signals, specifically the Pedal Demand Sensor 1 (PDS1) and the High-resolution Pedal Demand Sensor (HPDS). The PCM expects these two signals to track proportionally at all times, and when their correlation falls outside the calibrated tolerance, it stores this code and typically illuminates the wrench or check engine light.

SystemPowertrain

Code typeFord specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illumination of the check engine light or powertrain malfunction wrench light
Reduced engine power or limp-home mode with limited throttle response
Hesitation or stumble when pressing the accelerator pedal
Unintended idle flare or surging while cruising
Often no symptoms besides the warning light, especially if the fault is intermittent
Poor fuel economy or delayed downshifts due to incorrect pedal interpretation

Common causes, most likely first

Contaminated or worn accelerator pedal position sensor tracks inside the pedal assembly
Chafed, corroded, or loose wiring in the pedal sensor harness or connector
Poor electrical ground at the pedal sensor or PCM ground point
Failed accelerator pedal assembly (internal sensor drift or dead spot)
PCM software calibration issue or internal PCM fault affecting signal processing
Voltage reference or signal return circuit fault shared by the two pedal sensors

How to diagnose and fix it

Connect a scan tool and record live data for both PDS1 and HPDS while slowly sweeping the pedal through its full travel to confirm the correlation fault
Inspect the accelerator pedal connector and harness for corrosion, chafing, or loose pins, and repair any damaged wiring
Measure reference voltage and ground at the pedal sensor connector with a multimeter and compare to factory specifications
Check for Ford technical service bulletins (TSBs) or PCM calibration updates that address pedal correlation faults before replacing parts
Perform a wiggle test on the pedal harness while monitoring live data to expose intermittent connection faults
Replace the accelerator pedal assembly if sensor outputs are erratic or outside specification, then clear codes and verify correlation
If the fault persists after pedal replacement, diagnose the PCM and its ground circuits, including checking for water intrusion or terminal tension issues

Pedal correlation faults that fool good technicians

A dirty or worn accelerator pedal sensor often produces a correlation code before it sets a hard fault, so intermittent P1256 can be missed if you only check codes and not live data during a slow pedal sweep.
Many technicians replace the pedal assembly only to find a chafed wire in the harness near the brake pedal bracket or a corroded ground behind the kick panel, so always inspect the wiring before condemning the pedal.
P1256 can be set by a low battery or charging system issue that causes the PCM to misread sensor voltages during cranking, so check battery health and ground quality as part of the diagnosis.
On some Ford models, a PCM calibration update is required to correct a false correlation threshold, and replacing parts without checking for TSBs leads to repeat repairs.
The code does not always mean the pedal is failing; a faulty throttle body or electronic throttle control (ETC) motor can cause the PCM to cross-check pedal signals against throttle position and set P1256 as a secondary code.

Can I keep driving with P1256?

You can usually drive the vehicle to a repair shop, but expect reduced engine power and avoid heavy acceleration or highway merging until the fault is repaired. If the vehicle enters limp-home mode with severely limited speed, pull over safely and arrange a tow rather than risking a stall in traffic.

Tools that help

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Guidance is general and written for Ford vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.