Circuit Description
A toothed wheel mounted on the output shaft of the manual transmission generates an AC voltage pulse as it moves past the vehicle speed sensor (VSS). The VSS contains a permanent magnet surrounded by a coil of wire, which produces a magnetic field. The toothed wheel interrupts the magnetic field that generates an AC voltage pulse. As the vehicle speed increases the AC voltage pulse rate increases.
The PCM supplies the VSS signal (via the VSS output circuit) to the following components:
| • | Body Control Module (BCM) |
| • | Instrument Panel Cluster (IPC) |
| • | Electronic Suspension Control Module, if equipped |
Conditions for Running the DTC
| • | DTCs P0107, P0108, P0117, P0118, P0506, P0507, P1120, P1220, P1221 are not set. |
| • | The ECT is greater than 35°C (95°F). |
| • | The engine speed is greater than 1000 RPM. |
| • | The TP sensor angle is greater than 5 percent, but less than 100 percent. |
| • | The MAP is between 40 kPa (5.8 psi) and 99 kPa (14.3 psi) when the A/C is OFF. |
| • | The MAP is between 45 kPa (6.5 psi) and 99 kPa (14.3 psi) when the A/C is ON. |
| • | All conditions met for 2 seconds. |
Conditions for Setting the DTC
The PCM detects vehicle speed at 0 km/h (0 mph) for 1 minute and 40 seconds.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
Important:
• Remove any debris from the PCM\TAC module connector surfaces before
servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets
when diagnosing/replacing the modules. Ensure that the gaskets
are installed correctly. The gaskets prevent contaminate intrusion
into the PCM\TAC modules. • For any test that requires probing the PCM or a component
harness connector, use the Connector Test Adapter Kit J 35616
. Using this kit prevents damage
to the harness/component terminals. Refer to
Using Connector Test Adapters
in Wiring Systems.
| • | Inspect all of the circuits to the PCM and the VSS. Inspect the terminal connections at the VSS harness connector and at the PCM harness connector. If all of the circuits and connections are OK, replace the PCM. |
| • | For an intermittent, refer to Symptoms - Engine Controls in Engine Controls. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Important: Do Not perform this test without supporting the lower control arms so that the drive axles are in a normal horizontal position. Running the vehicle with the wheels hanging down at full travel may damage the drive axles. Does the scan tool indicate a vehicle speed above the specified value? | 15 mph (24 km/h) | Go to Diagnostic Aids | ||
3 |
Slowly bring the engine speed to 1500 RPM and hold. Does the DMM indicate a voltage above the specified value? | 1.2 V | ||
4 |
Is the test lamp illuminated? | -- | ||
5 |
Is the voltage above the specified value? | 0.2 V | ||
6 | Test the VSS high circuit for an open or short to ground. Repair if necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
7 | Repair the short to voltage on the VSS high circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
8 | Repair the open/high resistance in the VSS high circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
9 |
Important: Inspect the reluctor wheel on the transmission output shaft for damage. Replace the VSS. Refer to Vehicle Speed Sensor Replacement in Rear Drive Axle. Is the action complete? | -- | -- | |
10 | Repair the open in the VSS low circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
11 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls. Is the action complete? | -- | -- | |
12 |
Does the scan tool indicate that this test ran and passed? | -- | ||
13 | Select the Capture Info option and the Review Info option with the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
