GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1997 🢒 Safari - 2WD 🢒 DTC 🢒 DTC P0500 Vehicle Speed Sensor (VSS) Circuit

Circuit Description

The Vehicle Speed Sensor (VSS) circuit is of the magnetic induction type. The gear teeth are pressed on the outside diameter of the output shaft assembly. The gear teeth induce an alternating current in the sensor as the shaft rotates. The signal goes directly to the VCM. This pulsing action takes place about 40 times per revolution of output shaft of transmission. The VCM calculates the vehicle speed based on the time between pulses. This is a type A DTC.

Conditions for Setting the DTC
    • No MAP DTCs.
    • Throttle angle below 3.125 %.
    • Engine coolant temperature above 60° C.
    • Engine speed between 1400 RPM and 4400 RPM.
    • MAP is below 20 kPa.
    • All conditions met for at least 5 seconds.

Action Taken When the DTC Sets

The VCM turns ON the MIL when this DTC is reported and 1 failure has occurred.

Conditions for Clearing the MIL/DTC

The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.

Diagnostic Aids

Check proper calibration for the speedometer.

Test Description

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

  1. This step determines if the DTC P0500 is the result of a hard failure or an intermittent condition.

    2.

  2. This step checks the wiring, the connections, the VCM, and the VSS.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear Info function is used.

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Connect the scan tool.
  2. Clear the DTCs.
  3. Back probe across the VSS signal circuits High and Low using the J 35616 connector test adapter kit.
  4. Raise the wheels of the vehicle.
  5. Operate the engine in gear.
  6. Set the voltmeter on the AC 200 volt scale.

Is the voltage constant?

--

Go to Step 5

Go to Step 3

3

Does the voltage vary?

--

Go to Diagnostic Aids

Go to Step 4

4

Does the voltmeter read NO voltage?

--

Go to Step 11

Go to Step 12

5
  1. With vehicle still raised, disconnect the Vehicle Speed Sensor (VSS).
  2. Operate the engine.
  3. Transmission in gear.
  4. The voltmeter on the AC 200 scale
  5. Measure the voltage across the Vehicle Speed Sensor terminals A and B.

Does the voltage vary with the RPM?

--

Go to Step 7

Go to Step 6

6

Replace the Vehicle Speed Sensor. Refer to Transmission.

Is the action complete?

--

Go to Step 12

--

7
  1. Check for a poor connection at the VCM harness connector.
  2. Check for a poor connection at the Vehicle Speed Sensor connector.

Was a problem found?

--

Go to Step 9

Go to Step 8

8
  1. Check for an open or a short circuit between the VCM connector terminal for the VSS signal low circuit and the Vehicle Speed Sensor connector terminal A.
  2. Check for an open or a short circuit between the VCM connector terminal for the VSS signal high circuit and the Vehicle Speed Sensor connector terminal B.

Was a problem found?

--

Go to Step 10

Go to Step 12

9

Repair the connection as necessary. Refer to Wiring Repairs in Engine Electrical.

Is the action complete?

--

Go to Step 12

--

10

Repair the open or short as necessary. Refer to Wiring Repairs in Engine Electrical.

Is the action complete?

--

Go to Step 12

--

11

Replace the VCM.

Important:  If the VCM is faulty, program the new VCM. Refer to VCM Replacement/Programming .

Is the action complete?

--

Go to Step 12

--

12
  1. Using the scan tool, select the DTC and the Clear Info.
  2. Start the Engine.
  3. Idle at the normal operating temperature.
  4. Select the DTC and the Specific.
  5. Enter the DTC number which was set.
  6. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?

--

Go to Step 13

Go to Step 2

13

Using the scan tool, select the Capture Info and the Review Info.

Are any DTCs displayed that have not been diagnosed?

--

Go to The Applicable DTC Table

System OK