OBD-I Codes List

Ford 511 Read out memory test failure KOEO

Make
Ford (1981-1995)
Category
Powertrain - Computer and Auxiliary Controls
Severity
Check Engine Light

How to read it

Code 511 reads as 5 flashes, pause, 1 flash, pause, 1 flash 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 511 mean?

Read out memory test failure KOEO

Common causes of 511

  • Battery power was interrupted and the read out memory was cleared
  • An open power feed or blown fuse to the PCM memory circuit
  • Corroded or loose battery terminals and grounds
  • Low charging system voltage during the test
  • An internal PCM memory fault

How to fix 511

  1. Confirm the code and note whether battery power was recently interrupted
  2. Check the battery cables, grounds and the PCM memory fuse
  3. Measure battery and charging voltage under load
  4. Test the PCM last, only after every circuit test has passed
  5. Clear the code, then retest to confirm the fix holds

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 2026-10-10.

Report a correction for 511. Include your vehicle, the issue and a source if you have one.

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