For 1990-2009 cars

### Circuit Description

Vehicle speed information is provided to the PCM by the Vehicle Speed Sensor (VSS). The VSS consists of a magnetic pickup sensor mounted to the transmission case which interfaces with a rotor pressed onto to the transmission output shaft. The VSS produces a frequency signal that is proportional to vehicle speed. The PCM converts the VSS signal to vehicle speed, displayed on the scan tool in miles per hour and kilometers per hour. The PCM also uses the VSS signal to generate the 4000 pulses per mile vehicle speed signal used by the instrument cluster and the stepper motor cruise control module.

### Conditions for Setting the DTC

• | Engine speed is greater than 600 RPM.

• | Engine load and engine speed acceleration indicate that the vehicle is in gear.

• | Above conditions must be present for over 2 seconds.

• | Vehicle speed sensor indicates a speed of less than 5 km/h (3 mph) for greater than 10 seconds.

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.

• | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared by using the scan tool.

### Diagnostic Aids

The scan tool should display vehicle speed while the drive wheels are turning.If you suspect that an intermittent fault exists, check for the following conditions:

• | Poor connection at the PCM or the VSS -- Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

• | Damaged harness -- Inspect the wiring harness for damaged insulation. Check for bolts, brackets, etc.interfering with the wiring harness and rubbing through the wiring insulation.Damaged insulation can cause an intermittent condition.

• | Loose or damaged VSS rotor -- A damaged VSS rotor may cause an erratic or incorrect vehicle speed to be displayed.Refer to Manual Transmission section for on-vehicle service.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

1. If the condition that caused the DTC to set cannot be duplicated, checking the items referred to in Diagnostic Aids may isolate the cause of an intermittent fault.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn OFF the ignition switch.
2. Raise drive wheels
3. Start the engine and idle in gear.
4. Observe the vehicle speed display on the scan tool.

Does the scan tool display vehicle speed greater than the specified value?

0

Go to Diagnostic Aids

Go to Step 3

3 | Observe the cluster speedometer with the engine still idling in gear. Does the speedometer display vehicle speed greater than the specified value? | 0 | Go to Step 7 | Go to Step 4
4 |

1. Turn OFF the ignition switch.
2. Disconnect the VSS electrical connector.
3. Connect J 33431-C Signal Generator and Instrument Panel Tester to the VSS harness connector.
4. Turn ON the ignition switch.
5. Turn ON the Signal Generator, set signal generator to generate a VSS signal.
6. Observe the vehicle speed display on the scan tool.

Does the scan tool display vehicle speed greater than the specified value?

0

Go to Step 6

Go to Step 5

5 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Turn ON the ignition switch.
4. Check for the following conditions:

• | VSS High circuit open, shorted to ground, or shorted to voltage.

• | If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

5. VSS Low circuit open or shorted to voltage.

Was a problem found?

--

Go to Step 8

Go to Step 7

6 | Replace the VSS. Refer to Automatic Transmission On-Vehicle Service . Is the action complete? | -- | Go to Step 8 | --
7 | Replace the PCM. Important:: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 8 | --
8 |

1. Turn OFF the ignition switch.
2. Raise drive wheels.
3. Start the engine and idle in gear.
4. Observe vehicle speed display on the scan tool.

Does the scan tool display vehicle speed greater than the specified the specified value?

0

System OK

Go to Step 3