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 multifunction alarm module |
Conditions for Running the DTC
| • | DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0351, P0352, P0402, P0404, P0405, P0406, and P1404 are not set. |
| • | The engine coolant temperature (ECT) is more 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 TP sensor is less than or equal to 0.8 percent. |
| - | The engine speed is between 1,800-6,000 RPM. |
Conditions for Setting the DTC
The ECM detects that the vehicle speed is less than 5 km/h (3.1 mph) for more than 35 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 (I/P) 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):
- 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.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the VSS.
- Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal A and ground.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
- Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 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. |
- Test for 9-11 volts between the signal circuit terminal 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. |
- If the voltage is within the specified range, replace the VSS.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
