OBD-I Codes List

Ford 990 Transmission fluid pressure solenoid circuit malfunction during the KOEO test

Make
Ford (1981-1995)
Category
Powertrain - Transmission
Severity
Check Engine Light

How to read it

Code 990 reads as 9 flashes, pause, 9 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 990 mean?

Transmission fluid pressure solenoid circuit malfunction during the KOEO test

Common causes of 990

  • A transmission fluid pressure solenoid that fails the KOEO circuit check
  • An open or short in the TFP solenoid wiring during the KOEO test
  • A failed transmission fluid pressure solenoid
  • An internal fault in the PCM TFP driver

How to fix 990

  1. Run the KOEO test and confirm the TFP solenoid fault
  2. Check the transmission connector pins for the TFP solenoid for corrosion or a poor fit
  3. Test the TFP solenoid and replace it only if it fails its own test
  4. Test the PCM last, only after every circuit test has passed
  5. 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 990. Include your vehicle, the issue and a source if you have one.

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