P2166: Throttle/Pedal Position Sensor D Maximum Stop Performance

P2166 refers to position signal D, which on Ford designs is the first track of the accelerator pedal. The code means the reading with the pedal pressed all the way does not match the calibrated maximum, for instance because the pedal never reaches its stop or the track is worn at the far end. No manufacturer documents P2166 publicly; it applies the logic of the A version P2163 and of the open-stop learning in a Visteon patent to the pedal. A thick floor mat, a bent pedal arm or a worn pedal module are typical causes. The engine computer may then cap the torque request, so the car feels as if it never reaches full power. P2115 covers the rest position of D, P2120-P2124 its circuit, and P2138 the D/E correlation.

Symptoms

• Engine warning lamp on
• No kickdown or no full power with the pedal floored
• Possible limp mode

Most likely causes

• Floor mat or object keeps the pedal from its stop
• Pedal sensor track D worn at full travel
• Bent pedal arm or damaged pedal bracket
• Corroded pedal connector shifting signal D

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the pedal and throttle connectors
2. Compare the reading with other engine data while varying the engine speed.
3. Use live data to confirm that both sensors rise smoothly and consistently
4. Clean the throttle if it has carbon buildup
5. Run the relearn procedure with the scanner if the manufacturer requires it
6. Replace the part identified by the diagnosis

Good to know

• Repair difficulty: easy
• It can trigger limp mode.
• It affects emissions.

What each character of P2166 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 1: Air and fuel
• 66: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2166?

Be careful: the car may suddenly lose power. If it goes into limp mode, get off the highway and calmly make your way to a repair shop.

What causes code P2166?

The most common causes are: floor mat or object keeps the pedal from its stop; pedal sensor track D worn at full travel; bent pedal arm or damaged pedal bracket.

Related codes

• P2115Throttle/Pedal Position Sensor D Minimum Stop Performance
• P2167Throttle/Pedal Position Sensor E Maximum Stop Performance
• P2122Throttle/Pedal Position Sensor/Switch D Circuit Low
• P2138Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation

Sources

• patents.google.com: en
• newtonnet.co.uk: fordobd2012
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.