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DTC EO28 relevant for a 1992 STS?


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We have a guy on the sub forum Cadillac Club Sweden reporting an error on his 1992 STS and we have problems to come up with a relevant solution?

  • First the engine wouldn't start at all.
  • Then the service garage replaced the ECM and the engine started. The ECM now in place is told to be a restored one imported from the USA.
  • The car is now consuming 2.5 times as much fuel as before
  • The gearbox seems not to be in the mood for service – acts very slow in the beginning
  • When checking the OBD system he reports EO28 which I can't find in the list for a 1992 STS, It's not listed in the Service Manual either http://www.caddyinfo.com/stscodes.html
  • P028 (E028) ......... Open 3rd or 4th Gear Shift Or Shorted 2-3 Shift Solenoid [VCC] says the list for the OBD 1 system
  • Can anybody find a reasonable explanation to this situation – could the garage have put in an irrelevant ECM (4.6 L)? Any other ideas?

    Thanks /Bengt B)

    Moderator sub forum Cadillac Club Sweden

    Bengt Olsson

    Cadillac Club Sweden

    99 STS Vogue Gold Edition

    Corsa cat-back w gold tips

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    I dont have a '92 manual but I have a '93.

    The '92 should have the 4.9L. The '93's had either the 4.6L (northstar) or 4.9L available.

    The 1993 manual has diagnostics for both the 4.6L and 4.9L.

    'EO' was used for codes thru 1992. Starting in 1993 'PO' was used. Technically EO and PO codes are the same thing.

    There is no code EO/PO 28 listed for the 1993 4.9L.

    There IS a EO/PO 28 listed for the 1993 4.6L Northstar. "PO28: Transaxle pressure switch / circuit problem." 1993 service manual page 6e-a-94.

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