GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0503: Vehicle Speed Sensor (VSS) Circuit Intermittent

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Ignition

P0502, P0503

P0502, P0503

--

--

Signal

P0502, P0503

P0502, P0503

P0502, P0503

--

Ground

--

P0502, P0503

--

--

Circuit/System Description

The vehicle speed sensor (VSS) is mounted on the transaxle. As the transaxle turns the VSS, the VSS provides the speedometer with a vehicle speed input through voltage pulses. This input is used to drive the speedometer.

Conditions for Running the DTC

    • Ignition voltage is between 11 V and 18 V.
    • Raw output speed is greater than 3000 RPM.
    • Output speed change is less than 175 RPM.

Conditions for Setting the DTC

Loop to loop change in TOSS is greater than 3000 RPM.

Action Taken When the DTC Sets

DTC P0503 is a type B DTC.

Conditions for Clearing the DTC

DTC P0503 is a type B DTC.

Reference Information

Schematic Reference

    •  Automatic Transmission Controls Schematics
    •  Manual Transmission Schematics
    •  Manual Transmission Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

    •  Electronic Component Description
    •  Transmission System Description and Operation
    •  Transmission System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Operate the vehicle at 16-32 km/h (10-20 mph) while observing the scan tool VSS parameter. The reading should vary with the vehicle speed and not drop out.
  2. 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 observes from the Freeze Frame/Failure Records data.

Circuit/System Testing

  1. Ignition OFF, disconnect the VSS harness connector.
  2. Test for less than 10 Ω between the ground circuit and ground.
  3. • Automatic transmission terminal 2
    • Manual transmission terminal A
    If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the ignition circuit and ground.
  5. • Automatic transmission terminal 1
    • Manual transmission terminal C
    If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  6. Test for ignition V between the signal circuit and ground.
  7. • Automatic transmission terminal 3
    • Manual transmission terminal B
    If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the appropriate control module.
    • Automatic transmission TCM
    • Manual transmission ECM
  8. If all circuits test normal replace the VSS.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for ECM or TCM replacement, setup, and programming