P2123: Throttle/Pedal Position Sensor/Switch D Circuit High

What does P2123 mean?

P2123 is the high-voltage fault on pedal track D, usually an open sensor ground or a short to the 5 V reference or to battery voltage. GM's 2007 tables set it above 4.75 V (19 of 39 counts, Type A), a Bosch-based GM ECM from 2012 above 4.824 V lasting 0.2 s, and the 2014 VW Touareg above 4.89 V; Ford uses 4.75 V. A track pinned near the supply rail would read like a fully pressed pedal, so the controller rejects it, carries on with track E and caps engine output. GM PIP3783D lists the code among the very intermittent pedal faults on 2007-2014 full-size trucks and advises wiggling the harness and testing terminal tension. P2122 is the low counterpart, P2120 the general circuit code, P2128 the high fault on track E.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Engine warning lamp and reduced power message
• Limited throttle opening despite full pedal
• Fault may appear and vanish with harness movement

Common causes

• High Open or high-resistance ground return of the pedal sensor
• Medium Track D signal shorted to the 5 V reference or battery voltage
• Medium Internal pedal sensor fault
• Low Loose or spread terminals at pedal or inline connector

Likelihood is a general estimate across vehicles; your make and model may differ.