MODE 01 · PID 21

Distance with MIL on

This counter describes distance associated with MIL operation as reported by the ECU. It is not a predicted distance to component failure.

Formula
256 × A + B
Data bytes
2
Units
km

A worked decoding example

Request: 01 21

Response: 41 21 00 64

Data: 00 64 → 100 km

The example shows service, PID and data only. It omits adapter headers, CAN identifier, length and padding. It is not a live vehicle reading.

Reading context

Record current MIL and DTC status separately. Counter support and reset conditions must be checked against vehicle information.

A decoded value is a measurement, not a diagnosis. Encoding limits are not normal operating limits. Confirm vehicle support and the manufacturer’s procedure.

Byte decoder

Your input stays in this browser.MODE 01

Formula256 × A + B → km

A decoded value is a measurement, not a diagnosis. Encoding limits are not normal operating limits. Confirm vehicle support and the manufacturer’s procedure.

Sources

  1. python-OBD: Mode 01 command table ↗
  2. python-OBD: byte decoding implementation ↗
  3. CSS Electronics: OBD-II PID and response frames ↗
  4. California BAR: OBD test reference ↗

Independent reference; no affiliation with SAE, vehicle manufacturers or regulators. Sources checked 28 October 2026.