The vehicle speed information is provided to the engine control module (ECM) by the vehicle speed sensor (VSS). The VSS is a permanent magnet generator that is mounted to the transmission and produces a pulsing voltage. The AC voltage amplitude and frequency increases with vehicle speed. The ECM converts the pulsing voltage into km/h (mph).

The ECM detects that the vehicle speed is less than 5 km/h (3.1 mph) for more than 3 seconds.

DTC P0501 is a Type A DTC.

DTC P0501 is a Type A DTC.

Schematic Reference

Engine Controls Schematics

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Raise the drive wheels.

Caution: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel.

2. Support the lower control arms so that the drive axles are in a horizontal position.

Note: Engine running, engage the transmission into 2nd gear.

3. Engine running, observe the scan tool VSS data parameter. The following should display a vehicle speed once the drive wheels are at a speed above 5 km/h (3 mph):

•	The VSS data parameter

•	The speedometer

4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition OFF, disconnect the harness connector at the VSS.
2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal 1 or A and ground.

⇒	If greater than the specified range, repair the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 3 or C and ground.

⇒	If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.

4. Test for 9-11 volts between the signal circuit terminal 2 or B and ground.

⇒	If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

5. If the voltage is within the specified range, test or replace the vehicle speed sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.