Test Procedure

WARNING: This page does not describe the selected car, but rather 22 other vehicles, including the 2011 Mercury Milan, 2011 Mercury Mariner, 2011 Mercury Grand Marquis, 2011 Lincoln Town Car, and 2011 Lincoln Navigator L. However, it is still accessible from the selected car via links, so may be relevant.

DF1 CHECK FOR DIAGNOSTIC TROUBLE CODES (DTCS)

Is DTC U0121 present?

Yes	No
REFER to the appropriate Vehicle Dynamic Systems article, Symptom Charts, No communication with the ABS module.	GO to DF2.

DF2 VISUAL INSPECTION

Carry out the ABS self-test.

Are any DTCs present?

Yes	No
REFER to the appropriate Vehicle Dynamic Systems article, Symptom Charts, No communication with the ABS module.	GO to DF3.

DF3 CHECK THE PCM VEHICLE SPEED SIGNAL INPUT

WARNING: STRICT OBSERVANCE OF POSTED SPEED LIMITS AND ATTENTION TO DRIVING CONDITIONS ARE MANDATORY WHEN CARRYING OUT THE ROAD TEST. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.

Access the PCM and monitor the VSS (SPD) PID.
Road test the vehicle while monitoring the VSS PID.

Does the VSS PID increase and decrease while driving?

Yes	No
The concern is not present at this time. CHECK for a loose connection, and damaged or corroded terminals. WIGGLE the harness attempting to recreate the concern. REPAIR as necessary. Clear the PCM DTCs. REPEAT the self-test.	GO to DF4.

DF4 CHECK FOR CORRECT PCM OPERATION

Disconnect all the PCM connectors.
Visually inspect for:
- pushed out pins
- corrosion
Connect all the PCM connectors and make sure they seat correctly.
Carry out the PCM self-test.
Verify the concern is still present.

Is the concern still present?

Yes	No
INSTALL a new PCM. REFER to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) , PROGRAMMING THE VID BLOCK FOR A REPLACEMENT PCM .	The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.