Diagnostic Instructions
DTC Descriptor
DTC P0502: Vehicle Speed Sensor (VSS) Circuit
Circuit/System Description
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 supplies the VSS signal to the following components:
| • | The instrument panel for speedometer and odometer operation |
| • | The cruise control module |
| • | The multi-function alarm module |
Conditions for Running the DTC
| • | DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0201, P0202, P0203, P0204, P0300, P0351, P0352, P0402, P0404, P0405, P0406, and P1404 are not set. |
| • | The engine coolant temperature (ECT) is greater than 60°C (140°F). |
| • | The ignition 1 voltage is between 11-16 volts. |
| • | DTC P0502 runs continuously once the above conditions are met. |
| • | The following are additional Conditions for Running for the applicable test: |
Power Test
| • | The engine speed is between 1,200-4,000 RPM. |
| • | The throttle position (TP) sensor is between 25-60 percent. |
| • | The manifold absolute pressure (MAP) is more than 60 kPa. |
Deceleration Test
| • | The MAP is less than 30 kPa. |
| • | The change in engine speed per cycle is less than or equal to 50 RPM/cycle. |
| • | The throttle position (TP) sensor is less than or equal to 0.8 percent. |
| • | The engine speed is between 1,800-6,000. |
Conditions for Setting the DTC
The ECM detects that the vehicle speed is less than 5 km/h (3.1 mph) for greater than 37 seconds.
Action Taken When the DTC Sets
DTC P0502 is a Type B DTC
Conditions for Clearing the DTC
DTC P0502 is a Type B DTC
Diagnostic Aids
| • | Ensure the VSS is correctly torqued to the transmission housing. |
| • | This DTC may be set due to an instrument panel (IP) cluster condition. |
Reference Information
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
Circuit/System Verification
- Raise the drive wheels.
Notice: 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.
- Support the lower control arms so that the drive axles are in a horizontal position.
- Engine running, place the transmission into 2nd gear.
- Observe the scan tool VSS parameter.
The following should display a vehicle speed once the drive wheels are at a speed above 8 km/h (5 mph):
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the VSS.
- Ignition OFF, test for less than 5 ohms between the ground circuit terminal 1 and ground.
| ⇒ | If greater than the specified range, repair the ground circuit for an open/high resistance. |
- Ignition ON, test for battery voltage between the ignition voltage circuit terminal 3 and ground.
| ⇒ | If less than B+, repair the ignition voltage circuit for a short to ground, or an open/high resistance. |
- Test for 9-11 volts between the signal circuit terminal 2 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. |
- If the voltage is within the specified range, test or replace the VSS.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for engine control module replacement, setup, and programming.
