Circuit Description
The electronic control module (ECM) applies and monitors 12 volts on the signal wire between the vehicle speed sensor (VSS) and the ECM. The signal wire connects to the VSS which alternately grounds the signal wire when the drive wheels are turning. This pulsing action takes place 2,289 times per kilometer (3,683 times per mile) and the ECM will calculate vehicle speed based on the time between the pulses. This information is also displayed by the vehicle speedometer.
Conditions for Setting the DTC
| • | DTC 034 is not set. |
| • | The engine speed is between 2,000-5,000 RPM. |
| • | The VSS indicates a speed less than 6 km/h (4 mph). |
| • | The manifold absolute pressure (MAP) sensor signal indicates less than 24 kPa (3.4 psi). |
| • | These conditions are present for 2 seconds. |
Diagnostic Aids
Scan tool data should indicate a vehicle speed whenever the drive wheels are turning at more than 5 km/h (3 mph).
Step | Action | Yes | No |
|---|---|---|---|
1 | Was the Diagnostic System Check performed? | Go to Step 2 | |
2 |
Does the scan tool read vehicle speed? | Go to Diagnostic Aids | Go to Step 3 |
3 |
Is the test light ON? | Go to Step 9 | Go to Step 4 |
4 | With a test light connected to ground, momentarily touch the VSS connector terminal B several times a second. Does the scan tool read vehicle speed? | Go to Step 5 | Go to Step 11 |
5 | Connect a test light between the VSS connector terminal C and ground. Is the test light ON? | Go to Step 6 | Go to Step 7 |
6 |
Is the test light ON? | Go to Step 10 | Go to Step 8 |
7 | Repair the open wire between the VSS connector terminal C and the ignition switch. Is the repair complete? | System OK | Go to Step 2 |
8 | Repair the open wire between the VSS connector terminal A and ground. Is the repair complete? | System OK | -- |
9 | Repair the short to voltage in the wire between the VSS connector terminal B and the ECM connector terminal D10. Is the repair complete? | System OK | -- |
10 | Replace the VSS. Refer to Speedometer Driven Gear Replacement in Manual Transmission-D20. Is the repair complete? | System OK | -- |
11 |
Is the problem found? | Go to Step 12 | Go to Step 13 |
12 | Repair the open wire between the VSS connector terminal B and the ECM connector terminal D10. Is the repair complete? | System OK | -- |
13 | Replace the ECM. Refer to Engine Control Module Replacement . Is the repair complete? | System OK | -- |
