P2139: Throttle/Pedal Position Sensor/Switch D/F Voltage Correlation

What it means

Channels D and F of the throttle/pedal position sensor disagree by more than the allowed tolerance.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

Channels D and F are position signals monitored by the throttle or accelerator pedal control system, with their exact source depending on vehicle design. P2139 sets when the control module finds that D and F differ beyond the allowed relationship, which can come from a worn track, a wiring or connector problem, misalignment, or a control-module fault.

Common causes

Most likely first.

1. Worn or damaged sensor track in the throttle or pedal position sensor
2. Poor connector contact or damaged wiring
3. Sensor misalignment or mechanical wear
4. Fault in the throttle control module

Symptoms

• Check engine light on
• Reduced throttle response, possible limp mode
• Hesitation or surging
• Idle too high or too low

How to diagnose it

1. Record freeze-frame data and identify which component supplies channels D and F from the vehicle's scan data; graph both while slowly moving the pedal or throttle.
2. Inspect the D and F sensor connectors and harness for corrosion, loose pins, chafing, or damage, and check that the sensor assembly is securely mounted.
3. Check power, ground, and signal continuity for both channels using the wiring diagram, comparing results with the manufacturer's specification.
4. Compare the D and F signal curves across the operating range to locate a track that is worn, erratic, or mechanically out of alignment.
5. If the sensor and circuits pass, follow the manufacturer's procedure to assess throttle-control module inputs and outputs before condemning the module.

Common fixes

• Secure a loose sensor or repair a verified alignment or mounting problem.
• Clean and secure corroded or loose D/F connector terminals.
• Repair damaged wiring or poor power, ground, or signal connections on the affected channels.
• Replace the position-sensor assembly if either track fails testing.
• Repair or replace the control module only if its fault is confirmed after circuit and sensor checks.

Can I keep driving?

Avoid driving if throttle response is reduced or erratic, since the module may limit power or enter limp mode. If response is normal, drive only as needed for diagnosis; a worsening D/F mismatch can make acceleration unreliable.