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 Descriptor

DTC P0502: Vehicle Speed Sensor (VSS) Circuit - Low Frequency
DTC P0503: Vehicle Speed Sensor (VSS) Circuit Intermittent

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Operating Conditions: Engine Running, drive wheels turning.
VSS Signal | P0502, P0503 | P0502, P0503 | P0502, P0503 | P0503

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Operating Conditions: Engine Running, drive wheels turning.
VSS Signal | 0 km/h (mph) | 0 km/h (mph) | 0 km/h (mph) | --

### Circuit/System Description

The vehicle speed sensor is provided to the engine control module (ECM) by the vehicle speed sensor (VSS). The ECM provides a 5 volt circuit, a low reference circuit, and a signal circuit to the VSS. The VSS provides a frequency signal that is proportional to an increase in vehicle speed.

### Conditions for Running the DTC

#### P0502

The ignition is ON.

#### P0503

• | Ignition voltage is between 11-18 volts.

• | Engine speed is between 1500--6500 RPMs.

• | VSS signal is between 150-200 RPMs for 2 seconds.

### Conditions for Setting the DTC

#### P0502

VSS signal is less than 60 RPMs for 4.5 seconds.

#### P0503

VSS signal is greater than 350 RPMs for 3.25 seconds.

### Action Taken When the DTC Sets

P0502 and P0503 are Type B DTCs.

### Conditions for Clearing the DTC

P0502 and P0503 are Type B DTCs.

### Diagnostic Aids

The battery must be fully charged. Refer to Battery Inspection/Test.

### Reference Information

#### Schematic Reference

Manual Transmission Schematics

#### Connector End View Reference

Component Connector End Views

#### 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

Engine Control Module Scan Tool Information

### Circuit/System Verification

1. Operate the vehicle on the road at various speeds up to 64 km/h (40 mph), with a scan tool. The VSS parameter and the speedometer display on the instrument cluster should match.
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 observed from the Freeze Frame/Failure Records.

### Circuit/System Testing

1. Ignition OFF, disconnect the VSS harness connector at the transmission.
2. Test for less than 5 ohms between the low reference circuit at the VSS harness connector terminal A and ground.

⇒ | If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, test for greater than 4 volts between the 5 volt circuit at the VSS harness connector terminal C and ground.

⇒ | If less than the specified value, test the 5 volt circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

4. Ignition OFF, test for less than 1 volt on the signal circuit terminal B at the VSS harness connector.

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

5. Ignition OFF, disconnect the X1 connector at the ECM.
6. Ignition ON, install a 3 A fused jumper wire between B+ and terminal B at the VSS harness connector. Test for greater than 11 volts at X1 terminal 41 at the ECM harness connector.

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

7. If all circuits tests normal, replace the VSS.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Engine Control Module Replacement

• | Engine Control Module Programming and Setup