For 1990-2009 cars

### Circuit Description

The vehicle speed sensor (VSS) is located in the transmission assembly. The VSS incorporates a hall switch that generates a digital signal. The VSS sends this signal to the instrument cluster or the speedometer, the powertrain control module (PCM), and the cruise control servo, if equipped. The PCM converts the VSS signal into vehicle speed for use in engine and transmission operation.

### Condition for Running the DTC

• | The engine is running.

• | The vehicle is decelerating.

### Conditions for Setting the DTC

• | The engine is operating in Fuel Cut-off mode for more than 5 seconds.

• | No VSS signal is indicated.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

• | The PCM enters the Failsafe mode and limits air flow at the idle air control (IAC) valve.

### Conditions for Clearing the MIL/DTC

• | The MIL turns off after 3 consecutively passing trips without a fault present.

• | A history DTC clears after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function.

### Diagnostic Aids

A false DTC P0500 may set if there is no VSS signal to the PCM when the engine is operating in Fuel Cut-off mode. Observe the Vehicle Speed and the Fuel Cutoff Signal parameters on a scan tool while the vehicle is decelerating.

Check for a faulty cruise control servo assembly, if equipped. A malfunction in the cruise control module that causes the VSS signal to be pulled low can cause DTC P0500.

If the DTC P0500 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0500 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0500 appears in the Not Ran Since Code Cleared list, the P0500 diagnostic has not yet run. When the DTC P0500 does not appear in the Not Ran Since Code Cleared list, the P0500 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the P0500 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a fault in the VSS electrical circuit.

If DTC P0500 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions since the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Powertrain (OBD) System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step determines if a fault is present.

3. This step checks for the 5 volt reference signal from the PCM.

4. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0500 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0500 appears in the Not Ran Since Code Cleared list, the DTC P0500 diagnostic has not yet run. When the DTC P0500 does not appear in the Not Ran Since Code Cleared list, the DTC P0500 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0500 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Automatic Transmission Controls Schematics
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Install a scan tool.

Caution: To avoid any vehicle damage, serious personal injury or death when major components are removed from the vehicle and the vehicle is supported by a hoist, support the vehicle with jack stands at the opposite end from which the components are being removed and strap the vehicle to the hoist.

2. Raise and suitably support the vehicle drive axles. Refer to Lifting and Jacking the Vehicle in General Information.
3. Start the engine.
4. Put the gear selector in Low or engage the transmission in 1st gear.

Does the scan tool indicate a vehicle speed more than the specified value?

0 km/h (0 mph)

Go to Step 3

Go to Step 4

3 |

1. Lower the vehicle.
2. Perform the scan tool Clear DTC Information function.
3. Operate the vehicle within the conditions as specified in Running and Setting the DTC.

Does the scan tool indicate a DTC P0500?

--

Go to Step 5

Go to Diagnostic Aids

4 | Does the speedometer indicate vehicle speed? | -- | Go to Step 11 | Go to Step 5
5 |

1. Turn OFF the ignition.
2. Disconnect the electrical connector from the vehicle speed sensor (VSS) .
3. Turn ON the ignition, leaving the engine OFF.
4. Probe the ignition positive voltage circuit of the VSS electrical connector with a DMM connected to ground.

Is the voltage near the specified value?

12 V

Go to Step 6

Go to Step 8

6 |

1. Connect a test lamp to B+.
2. Probe the VSS ground circuit at the VSS electrical connector with the test lamp.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 13

7 |

1. Turn OFF the ignition.
2. Disconnect the PCM C4 electrical connector.
3. Probe the VSS signal circuit at the PCM, terminal C4-25, with a DMM connected to ground.
4. Turn ON the ignition, leaving the engine OFF.

Does the voltage equal the specified value?

5 V

Go to Step 9

Go to Step 15

8 | Repair the open circuit between S102 and the VSS. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 16 | --
9 |

1. Inspect for an open in the VSS signal circuit between the VSS and the PCM.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a wiring fault found and repaired?

--

Go to Step 16

Go to Step 10

10 |

1. Inspect the VSS signal circuit for a short to ground.

• | Between the PCM and the VSS

• | Between the cruise control module and S104

• | Between the instrument cluster and S215

2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a wiring fault found and repaired?

--

Go to Step 16

Go to Step 12

11 |

1. Inspect for an open in the VSS signal circuit between the PCM and S104.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a wiring fault found and repaired?

--

Go to Step 16

Go to Step 15

12 |

1. Inspect the transmission for a fault that prevents the VSS Hall switch circuitry from receiving a good physical signal.
2. Repair the transmission as necessary.

Was a transmission repair performed?

--

Go to Step 16

Go to Step 14

13 | Repair the faulty ground connection or the open in the VSS ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the wiring repair complete? | -- | Go to Step 16 | --
14 | Replace the VSS. Refer to Vehicle Speed Sensor Replacement in Automatic Transmission or to Vehicle Speed Sensor Replacement in Manual Transmission. Is the replacement complete? | -- | Go to Step 16 | --
15 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the replacement complete? | -- | Go to Step 16 | --
16 |

1. Turn OFF the ignition.
2. Remove the DOME fuse for 30 seconds.
3. Install the DOME fuse.
4. Reset the radio clock time. Refer to Radio/Audio System Description and Operation in Entertainment.
5. Start the engine.
6. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or until the DTC P0500 diagnostic test has run.

Does the DTC run and pass?

--

Go to Step 17

Go to Step 5

17 | Are any DTCs displayed on the scan tool? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK