For 1990-2009 cars

### 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 P0502: Vehicle Speed Sensor (VSS) Circuit Low Voltage

### 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.

• | Minimum throttle opening is greater than 15 %.

• | Engine torque is between 54 N·m and 8192 N·m.

• | Engine speed is between 1500 RPM and 6500 RPM.

### Conditions for Setting the DTC

Transmission output speed sensor (TOSS) raw speed is less than 48 RPM.

### 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.

### 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.

• | Automatic transmission terminal 2

• | Manual transmission terminal A

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

3. Ignition ON, verify that a test lamp illuminates between the ignition circuit and ground.

• | 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.

4. Test for ignition V between the signal circuit and ground.

• | 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

5. 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