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A throttle plate or its linkage stiff in its bore, so the actuator cannot move it freely to the commanded position. The module detects it by comparing command against feedback and reports a throttle actuator or idle control fault, which reads as an electrical problem in a part that is mechanically stuck.

Carbon is the usual cause and it accumulates where it matters most. Deposits build around the plate's edge and on the bore at the closed position — precisely where idle is controlled — so the fault shows worst at idle and light throttle and may be unnoticeable at larger openings. An unstable idle with normal wide-open performance is this pattern.

Cleaning is the repair, with two cautions. Many electronic throttle bodies have a coating that solvent and abrasion will remove, making the surface rougher and the problem worse, so use what the manufacturer permits. And cleaning almost always requires a relearn afterwards — the module has adapted to the old closed position over years, and removing the carbon changes it. Skipping the relearn produces a fresh set of codes on a throttle body that has just been correctly cleaned.