Powertrain, generic (extended)

P2AD3 Throttle/Pedal Position Sensor/Switch A/G Voltage Correlation

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P2AD3 compares tracks A and G. In GM's 2023 scheme A is the first sensor of the bank 1 throttle body and G the second sensor of the bank 2 unit, so the pair links both throttles of a V engine and can reveal that one plate is not where the other suggests. Mercedes-Benz is the documented user: on M177 V8s from the 2015 AMG C63 to the 2025 Maybach GLS 600, P2AD300 reads as an implausible relation between the A and G position values. Bulletin LI07.10-P-080384 already listed it in version 2 (May 2026) and blames raised contact resistance in the connectors M16/60 and M16/61 of the two throttle actuators. When P2135 or P2136 are stored alongside, a shared cause in the connectors is more likely than two failed throttles.

Likely causes

Raised contact resistance in the connectors of both throttle actuators

One throttle body with a faulty position sensor

Fault on a shared sensor supply or ground

Symptoms

Check engine light on
Possible loss of power or emergency throttle mode

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€150–900

Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

throttle position sensorthrottle position sensor gecm

Related codes

P2AD1 P2AD2 P2135 P2136 P212B

References: static.nhtsa.gov, static.nhtsa.gov, gsi.ext.gm.com.