Ford 650 Overdrive selection switch no signal change during the KOEO test
How to read it
Code 650 reads as 6 flashes, pause, 5 flashes, pause, 0 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 650 mean?
Overdrive selection switch no signal change during the KOEO test
Common causes of 650
- The overdrive switch was not operated during the KOEO test
- A failed overdrive selection switch
- An open or short in the overdrive switch circuit
- An internal fault in the PCM overdrive input
How to fix 650
- Operate the overdrive switch during the KOEO test as prompted
- Check the overdrive selection switch and replace it only if it fails its own test
- Check the overdrive switch circuit wiring for an open or short
- Test the PCM last, only after every circuit test has passed
- Clear the code, then retest to confirm the fix holds
Source
Qualified source review
Sources and review
Review: qualified. Read the source limits below.
- 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/
- Ford EEC-IV trouble code table: code, fault location, probable cause (Aerostar, Bronco, Econoline, Explorer, F-Series, Ranger 1992-1997)
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/aerostar-vanwagon-bronco-econolineclub-wagon-explorer-f-series-ranger-1992-1997/
Last updated 2026-10-10.
Report a correction for 650. Include your vehicle, the issue and a source if you have one.