Circuit Description
The vehicle speed information is provided to the engine control module (ECM) by the vehicle speed sensor (VSS). The VSS is a permanent magnet generator that is mounted to the transmission and produces a pulsing voltage. The AC voltage amplitude and frequency increases with vehicle speed. The ECM converts the pulsing voltage into km/h (mph). The VSS signal is also supplied to the following components:
| • | The instrument panel for speedometer and odometer operation |
| • | The clock |
| • | The HVAC control module |
If the ECM detects no vehicle speed for a calibrated amount of time, this DTC sets.
DTC Descriptor
This diagnostic supports the following DTC:
DTC P0501 Vehicle Speed Sensor (VSS) Circuit
Conditions for Running the DTC
| • | The engine is operating. |
| • | Vehicle speed does not change for at least 10 seconds. |
| • | Engine speed is greater than 2,100 RPM. |
| • | DTC P0501 runs continuously when the above conditions are met. |
Conditions for Setting the DTC
The ECM detects that the vehicle speed is less than 5 km/h (3.1 mph) for more than 35 seconds.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | Using the scan tool, can clear DTCs. |
| • | Disconnect the ECM battery feed for 10 seconds. |
Diagnostic Aids
| • | An intermittent condition may be caused by a poor connection, rubbed-through wire insulation, or a wire that is broken inside the insulation. |
| • | Ensure the VSS is correctly torqued to the transmission housing. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Descriptions
The numbers below refer to the step numbers on the diagnostic table.
-
Tests the signal circuit of the VSS for an open or a short to ground.
-
Tests the signal circuit of the VSS for a short to voltage.
-
Tests the ignition 1 voltage circuit of the VSS for an open or a short to ground.
-
Tests the ground circuit of the VSS for an open or high resistance.
Step | Action | Values | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||||||||
2 |
Notice: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel. Is the vehicle speed more than the specified value? | 0 km/h (0 mph) | Go to Step 3 | Go to Step 4 | ||||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||||||||
Is the voltage within the specified range? | 9-11 V | Go to Step 5 | Go to Step 8 | |||||||||||
Probe the signal circuit of the VSS with a test lamp connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 6 | |||||||||||
Measure the voltage at the ignition 1 voltage circuit of the VSS with a DMM. Is the voltage within the specified range? | 11-14 V | Go to Step 7 | Go to Step 12 | |||||||||||
Measure the resistance between the ground circuit of the VSS and battery ground with a DMM. Is the resistance less than the specified value? | 5 ohms | Go to Step 9 | Go to Step 13 | |||||||||||
8 | Test the VSS signal circuit for one of the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 11 | ||||||||||
9 |
Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 10 | ||||||||||
10 | Test for shorted terminals and poor connections at the VSS. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||||||
11 | Test for shorted terminals and poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 | ||||||||||
12 | Repair the ignition 1 voltage circuit between the VSS connector and the fuse for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 16 | -- | ||||||||||
13 | Repair the VSS ground circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 16 | -- | ||||||||||
14 | Replace the VSS. Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||||
15 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||||
16 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 17 | ||||||||||
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||
