Schematic Reference: Engine Controls Schematics
Circuit Description
The vehicle speed sensor (VSS) is located behind the I/P cluster assembly. The powertrain control module (ECM) supplies 5 volts to the VSS. The VSS incorporates a reed switch that opens and closes four times per revolution of the speedometer cable. The VSS signal voltage at the ECM toggles high and low when the reed switch opens and closes. The ECM converts the toggled high/low voltage into a vehicle speed reading that is displayed in km/h (mph).
Conditions for Setting the DTC
| • | Engine is operating in fuel cut mode for more than 5 seconds. |
| • | No vehicle speed sensor signal indicated. |
Action Taken When the DTC Sets
| • | The ECM illuminates the malfunction indicator lamp (MIL). |
| • | The ECM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
| • | The ECM enters the Fail-Safe Function and limits air flow at the IAC valve. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutively passing trips without a fault present. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the scan tool Clear DTC Information function or disconnect the ECM battery feed in order to clear the DTC. |
Diagnostic Aids
Check for a faulty speedometer cable. A binding speedometer cable may set a false DTC P0500. Make sure that the speedometer cable is free from any restrictions and that the cable has a secure connection to the I/P cluster assembly.
An intermittent malfunction may be caused by a fault in the VSS electrical circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connector locks. |
| • | Improperly formed or damaged terminals. |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, splices, or terminals. |
If the DTC P0500 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions since the DTC was first set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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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.
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This step determines if a fault is present.
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Review the Freeze Frame data in order to determine when the DTC set. Always record this information.
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This step checks for the 5 volt reference signal from the ECM. The VSS is located behind the I/P cluster assembly.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Does the scan tool display the vehicle speed above the specified value? | 0 km/h (0 mph) | |||
Does the scan tool indicate a DTC P0500? | -- | Go to Diagnostic Aids | ||
Is the voltage within the specified value? | 4 to 6 volts | |||
5 | Connect a test light to B+ and probe the I/P cluster assembly connector C2 terminal 10. Is the test light ON? | -- | ||
6 |
Was a repair necessary? | -- | ||
7 |
Was a repair necessary? | -- | ||
8 |
Was a repair necessary? | -- | ||
9 | Repair the faulty ground connection or the open in the VSS ground circuit. Is the action complete? | -- | -- | |
10 | Replace the speedometer assembly. Refer to Speedometer Replacement in Body and Accessories. Is the action complete? | -- | -- | |
11 | Replace the ECM. Refer to Engine Control Module Replacement. Is the action complete? | -- | -- | |
12 |
Are any DTCs displayed on the scan tool? | -- | Go to the Applicable DTC Table | System OK |
