A 2007 Ford Focus Mk II recently arrived in a German workshop with poor throttle response and two codes: P2125 and C1750. When a pedal code pairs with a manufacturer code, the diagnostic path splits between the cabin and the engine bay.
The Pedal Sensor Assembly
The P2125 code directly indicates a malfunction in the Accelerator Pedal Position (APP) sensor circuit. The pedal potentiometer degrades internally or fails entirely, sending inconsistent signals to the Powertrain Control Module (PCM). Our own data ranked this as the primary suspect at 90 percent probability with high severity.
To test the pedal assembly, mechanics need to check the APP sensor signal voltage using a multimeter. The next step is monitoring the APP-Sensor-E-PID in a live data stream with a diagnostic tool and performing a resistance test on the sensor itself.
Footwell Wiring and Fretting Corrosion
Ranked just behind the sensor at 85 percent probability is the wiring harness. The APP sensor wiring routes through the footwell. This environment invites moisture, abrasion from floor mats, and physical impact.
Fretting corrosion on the connector pins is a common issue here, interrupting circuit voltage and causing signal loss. The recommended steps are a visual inspection for cracked insulation, a continuity check of the cables using a multimeter, and a wiggle test on the harness while watching live data.
The Influence of C1750
While P2125 stays in the cabin, the internal Ford code C1750 points to the throttle body actuator and its position sensor. Ranked at 65 percent, this highlights that the PCM might be receiving the pedal command but failing to execute it at the throttle body.
Dirt, binding, or a failing actuator motor will mimic a bad pedal. Testing shifts to the engine bay. The technician should monitor the throttle position sensor signal in live data, visually inspect the throttle plate for carbon buildup or binding, and use a diagnostic tool to command the throttle motor.
PCM and Calibration Faults
If the pedal, wiring, and throttle body check out, Wrenchlane placed a PCM malfunction or outdated calibration at 50 percent probability. Bad processing of the APP signals or corrupted data can trigger both codes.
Technicians should check for manufacturer software updates via Technical Service Bulletins (TSBs). The final steps include diagnosing the PCM for internal fault codes and running an advanced test of the PCM input and output signals.
Next Steps for the Workshop
Drive-by-wire faults demand a structured approach rather than immediate parts replacement. Checking live data PIDs and performing continuity tests on the footwell wiring will isolate the fault before any components are ordered. If you see similar code pairings on older Ford models, test the footwell connectors before replacing the pedal.
Reference pages for the codes in this article
- P2125, what we measure for this code across real diagnostics
