What causes Ford code 46?

Secondary air was not bypassed during the self test. The AIR bypass solenoid failed and could not divert the air. A vacuum hose to the AIR system is damaged or connected wrong. The ignition coil primary circuit is open or the coil failed. The ECM could not bypass the air or fire the coil.

How do I fix Ford code 46?

Check the AIR bypass solenoid and confirm it diverts air during the self test. Check the vacuum hoses to the AIR system for damage or a wrong connection. Check the ignition coil primary circuit and the coil. Test the AIR bypass solenoid and the ignition coil and replace each only if it fails its own test. Test the ECM last, only after every circuit test has passed. Clear the code, then retest to confirm the AIR bypass and the coil both work.

Ford 46 Secondary air not bypassed during self test or ignition coil primary circuit fault

Q: What does Ford code 46 mean?

Ford code 46. Secondary air not bypassed during self test or ignition coil primary circuit fault.

Make: Ford (1981-1995)
Category: Powertrain - Auxiliary Emissions Controls
Severity: Check Engine Light

How to read it

Code 46 reads as 4 flashes, pause, 6 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 46 mean?

Secondary air not bypassed during self test or ignition coil primary circuit fault

Common causes of 46

Secondary air was not bypassed during the self test.
The AIR bypass solenoid failed and could not divert the air.
A vacuum hose to the AIR system is damaged or connected wrong.
The ignition coil primary circuit is open or the coil failed.
The ECM could not bypass the air or fire the coil.

How to fix 46

Check the AIR bypass solenoid and confirm it diverts air during the self test.
Check the vacuum hoses to the AIR system for damage or a wrong connection.
Check the ignition coil primary circuit and the coil.
Test the AIR bypass solenoid and the ignition coil and replace each only if it fails its own test.
Test the ECM last, only after every circuit test has passed.
Clear the code, then retest to confirm the AIR bypass and the coil both work.

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. Code 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 EEC-IV trouble codes, Crown Victoria, Mustang, Taurus, Thunderbird 1992-1995 (code, fault location, 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 additional probable causes.
https://web.archive.org/web/20160502051413id_/http://www.troublecodes.net:80/ford/crown-victoria-mustang-cobralxgt-taurus-thunderbird-1992-1995/
Ford EEC-IV trouble code table: code, fault location, probable cause (Crown Victoria, Mustang, Taurus, Thunderbird 1992-1995)
reference page (troublecodes.net)
Supports: per-code probable causes used for the page cause list and test order
Fetched 2026-09-30. The probable cause column is what the page lists, in source order, with the test order built from it.
https://www.troublecodes.net/ford/crown-victoria-mustang-cobralxgt-taurus-thunderbird-1992-1995/

Last updated 2026-10-10.

Report a correction for 46. Include your vehicle, the issue and a source if you have one.