Engine run time for Auxiliary Emissions Control Device (AECD)

Last reviewed 2026-08-31

Mode 01 · PID 81 (decimal 129)

Description

Run time of auxiliary emission-control devices (first block). Large multi-byte payload.

PID number

81 · 129

Unit

s

Range

—

Data bytes

41

Formula

AECD run-time block 1

• Also valid as Mode 02 freeze-frame data (same PID number, snapshot at last DTC).

Defined by SAE J1979 / ISO 15031-5. Public index — not a substitute for the paid SAE document.