Ford 312 AIR misdirected during KOER
How to read it
Code 312 reads as 3 flashes, pause, 1 flash, pause, 2 flashes on the check-engine light. Jumper the self-test input to signal return at the test connector, then run the key on engine off self test and the running self test, counting the check-engine flashes each time.
New to flash codes? The How to Read Ford EEC-IV Self-Test Codes walks through the test and what the numbers mean. The general OBD-I guide covers the rest.
What does Ford code 312 mean?
AIR misdirected during KOER
Common causes of 312
- Disconnected or leaking secondary air hose
- Faulty air pump, diverter or bypass valve
- Open or shorted wiring in the air control circuit
- Corroded connector at the air control solenoid
- Faulty PCM air control output
How to fix 312
- Confirm the code and read the flash sequence again
- Inspect the secondary air hoses for leaks and disconnects
- Test the air pump and control valves for operation
- Repair a hose or wiring fault before replacing parts
- Replace a failed valve or solenoid only after the tests
Source
Source review recorded
Sources and review
Review: checked against the recorded source material.
- EEC-IV Ford trouble code table (MIL, description, type)
archived reference page (troublecodes.net via Wayback Machine)
Supports: code identity and meaning
Fetched directly. The three-digit row matches the description used in the data file.
https://web.archive.org/web/20030720231430id_/http://www.troublecodes.net:80/Ford/eec-iv.shtml
- Ford trouble codes, Contour, Escort, Mustang, Probe, Taurus and Tempo 1992-1995 (code, description, probable cause)
archived reference page (troublecodes.net via Wayback Machine)
Supports: code identity and probable causes
Independent table on the same archive site with matching code identity and a probable cause column.
http://web.archive.org/web/20160501223306id_/http://www.troublecodes.net:80/ford/contour-escort-mustang-probe-taurus-tempo-1992-1995/
Last updated 2026-09-29.
Report a correction for 312. Include your vehicle, the issue and a source if you have one.