Fuel system status
Last reviewed 2026-08-31
Mode 01 · PID 03 (decimal 3)
Description
Open- or closed-loop status for fuel system 1 (byte A) and 2 (byte B). Values are enumerated (1 open-loop cold, 2 closed-loop, 4 open-loop load/decel, …).
- PID number
- 03 · 3
- Unit
- —
- Range
- —
- Data bytes
- 2
- Formula
- Bit encoded (open/closed loop)
Allowed values
| Value | Meaning |
|---|---|
| 0 | Motor off Engine not running. |
| 1 | Open loop — cold Open loop because the engine has not reached operating temperature. |
| 2 | Closed loop Closed loop using oxygen-sensor feedback to control fuel mixture. |
| 4 | Open loop — load or decel Open loop due to engine load, or fuel cut during deceleration. |
| 8 | Open loop — fault Open loop because of a system failure. |
| 16 | Closed loop — fault Closed loop using at least one oxygen sensor, but a fault exists in the feedback system. |
- Also valid as Mode 02 freeze-frame data (same PID number, snapshot at last DTC).
- Bit-encoded or enumerated — not a single scaled physical value.
Defined by SAE J1979 / ISO 15031-5. Public index — not a substitute for the paid SAE document.
Sources
Provenance for this page. Official standards outrank community notes. See the confidence policy.
Official standard · high trust
SAE J1979 / ISO 15031-5 Mode 01 PID formulas (public index)
J1979 public PID index: 01 03