Test Procedure

WARNING: This page does not describe the selected car, but rather 30 other vehicles, including the 2004 Mercury Sable, 2004 Mercury Mountaineer, 2004 Mercury Monterey, 2004 Mercury Marauder, and 2004 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.

DF1 DTCS P0500, P0503, P1501 AND P1502: CHECK THE VEHICLE SPEED CIRCUIT FOR INTERMITTENT CONCERNS

NOTE: PCM detected an error in the vehicle speed information received from the ABS control module. This test step checks for recurrence of this vehicle speed error.

Key ON Engine OFF.
Scan tool connector connected.
CLEAR the DTCs.
Take the vehicle to a suitable location and gradually increase the vehicle speed to 80 km/h (50 mph).
Coast down to an idle and stop the vehicle.
Key OFF.
Key ON Engine OFF.
CHECK Continuous Memory DTCs:

Are DTCs P0500, P0503, P1501 or P1502 present?

Yes	No
KEY OFF. The vehicle speed input was not as expected GO to DF2.	KEY OFF. The vehicle speed input was as expected. The fault that produced the original DTC may be intermittent. GO to DF6.

DF2 CHECK THE VSS AND VSS-GND FOR A SHORT TO POWER IN THE HARNESS

PCM connector disconnected.
ABS Module connector disconnected.
Key ON Engine OFF.
Measure the voltage between:

( + )PCM Connector, Harness Side	( - )
VSS - Pin 58	Ground
VSS-GND - Pin 33	Ground

Are the voltages less than 1 V?

Yes	No
GO to DF3.	KEY OFF. GO to DF7.

DF3 CHECK FOR AN OPEN VSS BETWEEN THE PCM AND ABS CONTROL MODULE

Measure the resistance between:

( + )PCM Connector, Harness Side	( - )ABS Module Connector, Harness Side
VSS - Pin 58	VSS - Pin 11

Is the resistance less than 5 ohms?

Yes	No
GO to DF4.	REPAIR open circuit. CARRY OUT the VSS Circuit Repair Verification Drive Cycle GO to DF8.

DF4 CHECK THE VSS-GND CIRCUIT FOR AN OPEN IN THE HARNESS

Measure the resistance between:

( + )PCM Connector, Harness Side	( - )
VSS-GND - Pin 33	Ground

Is the resistance less than 5 ohms?

Yes	No
GO to DF5.	REPAIR open circuit. CARRY OUT the VSS Circuit Repair Verification Drive Cycle GO to DF8.

DF5 CHECK THE VSS CIRCUIT(S) FOR A SHORT TO GROUND IN THE HARNESS

Scan tool connector disconnected.
Measure the resistance between:

( + )PCM Connector, Harness Side	( - )
VSS - Pin 58	Ground

Measure the resistance between:

( + )PCM Connector, Harness Side	( - )PCM Connector, Harness Side
VSS - Pin 58	VSS-GND - Pin 33

Are all the resistances greater than 10K ohms?

Yes	No
RESTORE vehicle. REFER to the appropriate ANTI-LOCK CONTROL article for further diagnosis of the ABS control module, its speed sensors and its wheel speed sensor harness circuits. If these components are working properly, INSTALL a new PCM. Refer to FLASH ELECTRICALLY ERASEABLE PROGRAMMABLE READ ONLY MEMORY - FLASH EEPROM . GO to DF8.	GO to DF7.

DF6 VISUAL INSPECTION

Visually inspect the VSS circuit harness and connectors at PCM, ABS and other VSS User Modules for damage, loose connections, loose grounds or incorrect routing.

NOTE: REFER to the appropriate SYSTEM WIRING DIAGRAMS article for harness, module and connector locations.

Did the visual inspection reveal a potential failure?

Yes	No
Repair the fault as necessary. GO to DF8.	Unable to duplicate or identify the fault at this time. REFER to the appropriate ANTI-LOCK CONTROL article for diagnosis of intermittent control module and wheel speed sensor concerns.

DF7 VERIFY IF THE VSS IS SHORTED IN HARNESS OR ANOTHER MODULE

Determine which, if any, modules are connected to the VSS circuit. Refer to the appropriate SYSTEM WIRING DIAGRAMS article. If no other modules are connected to the VSS circuit, GO to the YES Action To Take.
One at a time, disconnect the modules associated with the VSS. After disconnecting each module, TEST again for a short circuit. Refer to test step that sent you here). Repeat until each associated module is disconnected or the short circuit is eliminated.

Did the short circuit remain after all associated modules were disconnected?

Yes	No
REPAIR short circuit. GO to DF8.	REFER to the appropriate article for further diagnosis of the appropriate module. After the repair, RESTORE the vehicle. GO to DF8.

DF8 VSS CIRCUIT REPAIR VERIFICATION DRIVE CYCLE

NOTE: Warm the engine to normal operating temperature before continuing.

NOTE: Carry out the VSS circuit drive cycle at least 3 times as described below.

Automatic Transmission Drive Cycle:
- Place the transmission range selector lever in DRIVE range.
- Accelerate heavily to 56 km/h (35 mph).
- Coast down to an idle and stop the vehicle.
- Cycle the key OFF and ON.
Manual Transmission Drive Cycle:
- Shift from first to second gear.
- Accelerate moderately to 64 km/h (40 mph).
- Coast down to an idle and stop the vehicle.
- Cycle the key OFF and ON.
Key OFF.
Key ON Engine OFF.
CHECK Continuous Memory DTCs:

Are DTCs P0500, P0503, P1501 or P1502 present?

Yes	No
Disregard the current Diagnostic Trouble Code (DTC) at this time. Address the next DTC. Go to POWERTRAIN DTC CHARTS & DESCRIPTIONS - CNG, FLEX-FUEL & GASOLINE for DTC charts.	The repair has been verified.