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Diagnostic Circuit Check

  1. If complaint is "CHECK ENGINE" lamp related, this check will lead to most likely problem area, if malfunction exists. Enter diagnostics and record stored trouble codes. Begin diagnosis with lowest numbered code which is displayed and refer to appropriate trouble code chart.
  2. If code "51" is displayed, refer to PROM removal and installation in this article for diagnosis of this code.
  3. If code "52" or "53" is displayed, check PROM installation before replacing ECM. Refer to ECM removal and installation.
  4. If codes "54" or "55" are displayed with another code, always refer to diagnostic chart for code "54" or "55" first, then proceed to next lowest numbered code.
    NOTE: Any time codes "51", "52", "53", "54" or "55" are displayed with another code, start with "50-series" code first, then proceed to next lowest numbered code.
  5. If codes "14" and "21" or "15" and "21" are displayed, start with code "21" first, then proceed to code "14" or "15".
  6. On 2.5L engines only, if codes "13" and "34" are displayed, start with code "34" first, then proceed to code "13".
  7. If "intermittent failure" codes "13", "15", "24", "44", "45" or "55" are displayed, use diagnostic chart for corresponding "hard failure" code.
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