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 P0501: Vehicle Speed Sensor (VSS) Performance
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 Voltage | P0502 | P0502 | -- | P0501
Signal | P0502 | P0502 | P0502 | P0501
Ground | -- | P0502 | -- | P0501

### Typical Scan Tool Information

#### Vehicle Speed Sensor Parameter

Circuit | Short to Ground | Open/High Resistance | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine running, in gear, drive wheels rotating. Parameter Normal Range: Displays km/h (mph)
Ignition Voltage | 0 km/h (mph) | 0 km/h (mph) | --
Signal | 0 km/h (mph) | 0 km/h (mph) | 0 km/h (mph)
Ground | 0 km/h (mph) | 0 km/h (mph) | --

### Circuit/System Description

Vehicle speed information is provided to the engine control module (ECM) by the vehicle speed sensor (VSS). The VSS consists of a hall-effect sensor mounted to the transmission case which interfaces with a rotor pressed onto the transmission output shaft. The hall-effect sensor contains a permanent magnet and a semiconductor plate to which ignition voltage is applied. As the output shaft spins, the rotor directs the field of the permanent magnet either toward or away from the plate. The VSS produces a frequency signal that is proportional to vehicle speed. The ECM converts the VSS signal to vehicle speed, displayed on the scan tool in kilometers per hour or miles per hour. The ECM also uses the VSS signal to generate the 4,000 pulses per mile vehicle speed signal used by the instrument cluster.

### Conditions for Running the DTC

• | The engine speed is greater than 1800 RPM for 3 seconds.

• | The engine coolant temperature (ECT) is greater than 40°C (104°F).

### Conditions for Setting the DTC

The VSS indicates a speed of less than 0 km/h (0 mph) for 4 seconds.

### Action Taken When the DTC Sets

• | P0501 and P0502 are Type B DTCs.

• | The ECM disables cruise control.

### Conditions for Clearing the MIL/DTC

P0501 and P0502 are Type B DTCs.

### Diagnostic Aids

The battery must be fully charged and pass a battery test. 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

Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information.

### Circuit/System Verification

1. Operate the vehicle on the road at 64 km/h (40 mph). Observe the transmission vehicle speed sensor parameter with a scan tool. The VSS signal should match the instrument panel speedometer indicator.
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 X2 harness connector at the ECM.
2. Disconnect the VSS harness connector.
3. Ignition OFF, test for less than 5 ohms of resistance between the ground circuit at the VSS harness connector terminal 3 and ground.

⇒ | If greater than the specified value, repair the open/high resistance condition.

4. Ignition ON, test for less than 1-volt between the signal circuit terminal 1 and ground at the VSS harness connector.

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

5. Ignition ON, test for greater than 11-volts between the ignition voltage circuit, at the VSS harness connector terminal 3, and ground.

⇒ | If less than the specified value, test the ignition voltage circuit for a short to ground or an open/high resistance.

6. Ignition ON, install a 3A fused jumper wire between the ignition voltage circuit terminal 3 and the signal circuit terminal 1 at the VSS harness connector. Test for greater than 11-volts at X2, terminal 43 of 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.

7. Remove the 3A fused jumper wire.
8. Ignition ON, engine OFF, transmission in NEUTRAL.
9. Install a 3A fused jumper wire between the ignition voltage circuit terminal 1 on the VSS harness connector and terminal 1 on the VSS. Connect a second jumper wire between the ground circuit terminal 2 on the VSS harness connector and terminal 2 on the VSS.
10. Test for greater than 0.15-volts AC, at terminal 1 on the VSS sensor, while rotating the rear wheels by hand.

⇒ | If less than the specified value, replace the VSS.

11. If all circuits test normal, replace the ECM.

### Component Testing

1. Remove the VSS sensor. Refer to Vehicle Speed Sensor Replacement.
2. Inspect and repair the VSS or the transmission for the following conditions:

• | Loose or damaged VSS

• | Excessive VSS to rotor gap

• | Incorrect VSS rotor alignment

• | Loose or damaged VSS rotor

### Repair Instructions

• | Vehicle Speed Sensor Replacement

• | Engine Control Module Programming and Setup

• | Engine Control Module Replacement

### Repair Verifications

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.