What does this code mean?
The wording below belongs to the named make and communication. Match the complete code, reporting module, model year and engine before applying it.
A code identifies a detected condition, not a part that must automatically be replaced.
Manufacturer wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
C1991MODULE CALIBRATION FAILUREC1991MODULE CALIBRATION FAILUREC1991MODULE CALIBRATION FAILUREManufacturer communications
4Original wording in English
FORD, MERCURY
Reported code forms C1991
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…
FORD, LINCOLN
Reported code forms C1991
THIS ARTICLE ADDRESSES THE PROPER PROCEDURE TO CLEAR DIAGNOSTIC TROUBLE CODES C1990 OR C1991 FROM THE VEHICLE DYNAMICS MODULE/4-WHEEL AIR SUSPENSION MODULE. *TT
FORD, LINCOLN
Reported code forms C1991
DIAGNOSTICS FOR DIAGNOSTIC TROUBLE CODE C1991 IN THE ABS (ANTILOCK BRAKE SYSTEM) MODULE - OMITTED FROM WORKSHOP MANUAL - PROCEDURE PROVIDED. *TT
FORD, LINCOLN
Reported code forms C1991
DIAGNOSTIC PROCEDURES FOR DIAGNOSTIC TROUBLE CODE C1991 (MODULE CALIBRATION FAILURE) OMITTED FROM THE WORSHOP MANUAL. *TT
Check vehicle applicability
4A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
| Make | Model | Model year |
|---|---|---|
| Ford | EXPEDITION | 2003 |
| Ford | FREESTAR | 2004 |
| Lincoln | NAVIGATOR | 2003 |
| Mercury | MONTEREY | 2004 |
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.