DTC P0500 Vehicle Speed Sensor (VSS) Circuit. Geo Prizm 1997

For 1990-2009 cars

Schematic Reference: Refer to Engine Controls Schematics

### Circuit 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 (voltage pulses). This input is used to drive the speedometer. The speedometer then converts the vehicle speed input into a more precise signal and provides the Powertrain Control Module (PCM) and the Cruise Control Module with its own vehicle speed input. The PCM converts this input (ground pulses) into a vehicle speed.

### Conditions for Setting the DTC

#### Manual transaxle Vehicle

No vehicle speed sensor signal to PCM, when the vehicle speed is above 3 mph.

#### Automatic Transaxle Vehicle

• | Park/Neutral position switch is "OFF."

• | Vehicle speed is above 3 mph.

### Action Taken When the DTC Sets

• | The PCM will illuminate the MIL.

• | The PCM will store the conditions which were present when the DTC set as Freeze Frame Data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL "OFF" on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.

• | A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.

• | A DTC can be cleared by using the scan tool "Clear Information" function or by disconnecting the PCM battery feed.

### Diagnostic Aids

• | A scan tool should indicate a vehicle speed whenever the drive wheel is turning greater than 3 mph (5 km/h). DTC P0500 can be falsely set if the engine is "brake-torqued" in gear. Disregard if set while the drive wheels are not turning.

• | An intermittent malfunction may be cause by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation. Inspect harness connectors for backed out terminals, improper matting, broken locks, terminal-to wire connection before component replacement.

• | The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

• | Check G202 for a clean and tight connection.

### Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The 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. Checks whether the PCM is receive a signal from the vehicle speed sensor.

3. This step checks whether DTC P0500 is the result of a hard failure or an intermittent condition.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | 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. Raise the drive wheels.
2. Support the lower control arms so that the drive axles are in a horizontal (straight) position.
3. Allow the engine to idle in gear.
4. Observe vehicle speed on the scan tool.

Does scan tool display vehicle speed above the specified value?

0 mph

Go to Step 3

Go to Step 4

3

1. Clear the DTC.
2. Using the scan tool, place the vehicle into Check Mode.
3. Operate vehicle within the "Freeze Frame" conditions as noted.

Does DTC P0500 set?

--

Go to Step 4

Go to Diagnostic Aids

4 | Does the vehicle speedometer operate? | -- | Go to Step 5 | Go to Step 7

5

1. Disconnect the cruise control module connector. (if equipped)
2. Disconnect instrument cluster connector C2.
3. Turn the ignition switch ON.
4. Using a DMM, measure voltage at VSS connector C2 cavity 12.

Does the DMM read within specified value?

4-6 V

Go to Step 6

Go to Step 11

6

1. Turn the ignition switch OFF.
2. Reconnect instrument cluster connector C2.
3. Using a DMM, backprobe the connector C2 cavity 12 of the instrument cluster.
4. Raise and suitably support vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
5. Turn the ignition switch ON.
6. Measure voltage while slowly rotating the front drive wheel with transaxle in gear.

Does DMM vary in voltage within specified range?

0-5 V

Go to Step 20

Go to Step 18

7

1. Turn the ignition switch ON.
2. Using a DMM, measure voltage at the VSS connector cavity 1.

Does DMM read more than specified value?

10 V

Go to Step 8

Go to Step 12

8 | Probe the VSS connector cavity 2 with a test light connected to battery voltage Does the test light illuminate? | -- | Go to Step 9 | Go to Step 13
9 | Using a DMM, measure voltage at instrument cluster connector C3 cavity 12. Does the DMM read more than specified value? | 10 V | Go to Step 10 | Go to Step 14

10

1. Reconnect the VSS connector.

Important: All 3 connectors to instrument cluster must be plugged in.

2. Using a DMM, backprobe the instrument cluster connector C2 cavity 6.
3. Raise and suitably support vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
4. Measure voltage while slowly rotating the front drive wheel with transaxle in gear.

Does DMM vary in voltage within specified value?

0-10 V

Go to Step 16

Go to Step 15

11

1. Check vehicle speed input control circuit for an open or short between instrument cluster and PCM.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 20

12 | Check for an open or short in the ignition power feed between VSS and junction block 1. Is the action complete? | -- | Go to Step 21 | --

13

1. Check for an open in VSS ground circuit between VSS and instrument cluster or between instrument cluster and G202.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 19

14 | Check for an open or short between ignition power feed and junction block 3. Is the action complete? | -- | Go to Step 21 | --

15

1. Check VSS input circuit between VSS and instrument cluster
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 17

16

1. Check for the instrument cluster printed circuit for cracks or bad connection to speedometer.
2. Replace as necessary.

Did printed circuit need replacement?

--

Go to Step 21

Go to Step 18

17 | Replace the VSS. Is the action complete? | -- | Go to Step 21 | --
18 | Replace the speedometer. Is the action complete? | -- | Go to Step 21 | --
19 | Replace the instrument cluster printed circuit. Is the action complete? | -- | Go to Step 21 | --
20 | Replace the PCM. Refer to Powertrain Control Module Replacement. Is the action complete? | -- | Go to Step 21 | --
21 | After repairs, use the scan tool clear information function and road test vehicle within "Freeze Frame" conditions that set the DTC. Check for DTC(s). Review scan tool data and if no DTC(s) are stored repair is complete. Are any DTC(s) displayed on scan tool? | -- | Go to the applicable DTC table | System OK