C1991 on the 2004 Mercury Monterey
The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.
This code is specific to a manufacturer and is not described here. Its meaning is in the manufacturer's service information.
| 04125 | 2004-07-24. Service bulletin. DIAGNOSTIC TROUBLE CODE (DTC) C1991 (MODULE CALIBRATION FAILURE) - ANTI-LOCK BRAKE, ADVANCED TRAC, INTERACTIVE VEHICLE DYNAMICS (IVD), TRACTION CONTROL SYSTEM - SERVICE TIP. ALSO INCLUDES FORD FREESTAR MY2005 AND MERCURY MONTEREY MY2005. *TT |
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1 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.