the VSS is in the top of the rear diff on an '06 6.0L. Not in the transmission. The VSS sensor also sends signal to the ABS module. There are three speed sensors on an '06, one on the rear diff, and one on each front hub. VSS Ford pt# is F85Z-2L373-AB. Refer to pinpoint test G, (Inaccurate Speedometer Indication) section in the workshop manuals.
2006 F-Super Duty 250-550 Workshop Manual
Pinpoint Test G: Inaccurate Speedometer Indication
Normal Operation
The vehicle speed signal (VSS) is generated in the anti-lock brake system (ABS) and sent to the powertrain control module (PCM). The PCM transmits the VSS data to the instrument cluster over the communication network. If the instrument cluster fails to receive the VSS input from the PCM, the instrument cluster indicates 0 km/h (0 mph) on the speedometer.
* Possible Causes ABS concern
* ABS module
* instrument cluster
PINPOINT TEST G: INCORRECT SPEEDOMETER INDICATION
Test Step Result / Action to Take
G1 RETRIEVE THE RECORDED ABS MODULE AND PCM DTCs FROM BOTH THE CONTINUOUS AND ON-DEMAND SELF-TESTS
* Check for recorded ABS module and PCM DTCs from both the continuous and on-demand self-tests.
* Are any ABS or PCM DTCs recorded?
Yes
For ABS module DTCs, REFER to Section 206-09.
For PCM DTCs, REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.
No
GO to G2.
G2 CARRY OUT THE INSTRUMENT CLUSTER SPEEDOMETER ACTIVE COMMAND USING THE SCAN TOOL
* Ignition ON.
* Enter the following diagnostic mode on the diagnostic tool: Instrument Cluster Active Command.
* Select the instrument cluster speedometer active command and scroll the speedometer in increments of 10% while monitoring the speedometer. The speedometer should increase in increments of approximately 16 km/h (10 mph) for each 10% change.
* Does the speedometer reading increase within the specifications?
Yes
GO to G3.
No
GO to G7.
G3 VERIFY THE SPEEDOMETER CONCERN
* Test drive the vehicle and observe the speedometer operation.
* Does the speedometer operate smoothly as the vehicle speeds increase and decrease?
Yes
GO to G4.
No
INSPECT the ABS wheel speed harnesses and connectors for damage, corrosion or water, wheel speed sensors and the ABS harness for correct routing. REFER to Section 206-09.
G4 CHECK FOR STICKING STEPPER MOTOR
* Observe the speedometer with the vehicle stopped (no VSS).
* Does the speedometer pointer indicate 8 km/h (5 mph) or more?
Yes
GO to G7.
No
GO to G5.
G5 CHECK THE PCM VEHICLE SPEED SENSOR (VSS) PID
* NOTE: This step may require the use of an assistant to monitor and record the scan tool data. Enter the following diagnostic mode on the diagnostic tool: PCM PID.
* NOTE: The speedometer should register approximately the same speed as the VSS PID ±8 km/h (5 mph).
* Monitor the PCM VSS PID while driving the vehicle at 32 km/h (20 mph), 64 km/h (40 mph) and 97 km/h (60 mph).
* Does the speedometer indication agree with the PCM VSS PID within specification?
Yes
GO to G6.
No
GO to G7.
G6 CHECK THE ABS MODULE CONFIGURATION
* Ignition ON.
* Enter the following diagnostic mode on the diagnostic tool: ABS Module Configuration.
* Verify the tire size and axle ratio is correctly configured in the ABS module. Refer to Section 418-01.
* Is the ABS module configured correctly?
Yes
GO to G8.
No
RECONFIGURE the ABS module with the correct tire size and axle ratio. REFER to Section 418-01.
G7 CHECK FOR CORRECT INSTRUMENT CLUSTER OPERATION
* Disconnect all the instrument cluster connectors.
* Check for:
o corrosion
o damaged pins
o pushed-out pins
* Connect all the instrument cluster connectors and make sure they seat correctly.
* Operate the system and verify the concern is still present.
* Is the concern still present?
Yes
INSTALL a new instrument cluster. REFER to Instrument Cluster (IC) in this section. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. TEST the system for normal operation.
G8 CHECK FOR CORRECT ABS OPERATION
* Disconnect all the ABS connectors.
* Check for:
o corrosion
o damaged pins
o pushed-out pins
* Connect all the ABS connectors and make sure they seat correctly.
* Operate the system and verify the concern is still present.
* Is the concern still present?
Yes
INSTALL a new ABS module. REFER to Section 206-09. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. TEST the system for normal operation.