For 1990-2009 cars

## DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Input Manual Trans. Only

Engine Controls Components
VSS and Cruise Control
OBD II Symbol Description Notice
Engine Controls Connector End Views
Handling ESD Sensitive Parts Notice

### Circuit Description

Vehicle speed information is provided to the Powertrain Control Module (PCM) by the vehicle speed sensor (VSS). The VSS is a permanent magnet generator that is mounted in the transaxle and produces a pulsing voltage whenever vehicle speed is over about 3 mph (5 km/h). The AC voltage level and the number of pulses increases with vehicle speed. The PCM converts the pulsing voltage into km/h (mph) and then supplies the necessary signal to the instrument panel for speedometer, odometer operation and to the cruise control module and multi-function alarm module operation.

### Conditions for Setting the DTC

• | Vehicle speed is less than 2 mph (3 km/h).

• | Engine speed is between 1700 and 3600 RPM.

• | Throttle Position (TP) is between 8% and 20%.

• | Engine vacuum is between 38-55 kPa.

• | Above conditions met for 5 seconds.

• | DTCs P0107, P0108, P0122, and P0123 not set.

### Action Taken When the DTC Sets

• | The malfunction indicator lamp (MIL) illuminates.

• | The PCM records the operating conditions at the time when the diagnostic fails. This information stores in the Freeze Frame and Failure Records buffers.

• | A history DTC stores.

• | The coolant fan turns ON.

### Conditions for Clearing the MIL/DTC

• | The MIL will turn OFF after three 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.

• | The MIL/DTCs can be cleared by using the scan tool.

### Diagnostic Aids

• | An Intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.

• | VSS high and low CKT(s) should be thoroughly checked for the following conditions:

- | Backed out terminals

- | Improper mating

- | Broken locks

- | Improperly formed

- | Damaged terminals

- | Poor terminal to wiring connections

- | Physical damage to the wiring harness or for proper routing

• | Ensure the VSS is correctly torqued to the transmission housing.

• | Refer to Intermittent Conditions .

### Test Description

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

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records 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 on the scan tool for later reference.

2. The permanent magnet generator only produces a signal if the drive wheels are turning greater than 3 mph (5 km/h). This step determines if DTC P0502 is the result of a hard malfunction or an intermittent condition.

3. Proper engine loads cannot be achieved in a shop environment to properly run the vehicle within the Freeze Frame Data conditions. It will be necessary to drive the vehicle on the road to obtain the proper engine loads.

4. This step verifies that the PCM is receiving a signal from the vehicle speed sensor.

5. Refer to service bulletin information for the latest calibration update.

6. Refer to the latest Techline information for programming procedures.

7. A resistance reading that is higher than the specified value indicates that the VSS circuitry is open.

8. If the displayed resistance were less than the 1300 ohms, the VSS high and low circuits are shorted together. If the resistance value within the specified value, check the VSS high and low circuits for a short to ground.

9. This checks the resistance of the VSS if no opens or shorts were found on the VSS high and low circuits.

10. The replacement PCM must be programmed and the crankshaft position system variation procedure must be preformed. Refer to the latest Techline procedure for PCM reprogramming and also refer to the Crankshaft Position System Variation Procedure.

#### DTC P0502-Vehicle Speed Sensor (VSS) Circuit Low Input (Manual Trans.)

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

Notice: In order to avoid damage to the drive axles, support the lower control arms in the normal horizontal position. Do not run the vehicle in gear with the wheels hanging down at full travel.

1. Turn the ignition switch ON, with the engine OFF.
2. Install a scan tool.
3. Raise the drive wheels.
4. Support the lower control arms so that the drive axles are in a horizontal (straight) position.
5. Allow the engine to idle in gear.

Does the scan tool display vehicle speed above the specified value?

0 MPH

Go to Step 3

Go to Step 4

3 |

1. Turn the ignition switch ON, with the engine OFF.
2. Review the Freeze Frame data and note the parameters.
3. Operate the vehicle within the Freeze Frame conditions and Conditions For Setting The DTC as noted.

Does the scan tool display the vehicle speed above the specified value?

0 MPH

Go to Step 14

Go to Step 4

4 |

1. Turn the ignition switch OFF.
2. Disconnect the PCM connectors.
3. Connect a DVM between the VSS high and the VSS low terminals.
4. Rotate the drive wheels and measure the AC voltage.

Is the AC voltage greater than or equal to the specified value?

0.5V

Go to Step 5

Go to Step 7

5 | Check for the most current calibration ID. number. Is the latest calibration ID. in the vehicle? | -- | Go to Step 13 | Go to Step 6
6 | Update the PCM with the latest calibration ID. Is the action complete? | -- | Go to Step 14 | --
7 | Using a DVM, measure the resistance between the VSS high and VSS low PCM electrical connector terminals. Is the resistance greater than the specified value? | 870 ohms | Go to Step 8 | Go to Step 9
8 | Check the VSS high circuit for an open and repair as necessary. Was a repair necessary? | -- | Go to Step 14 | Go to Step 11
9 | Was the resistance value within or equal to the specified value? | 530-870ohms | Go to Step 10 | Go to Step 11
10 | Check the VSS high circuit for a short to ground or for being shorted together and repair as necessary. Was a repair necessary? | -- | Go to Step 14 | Go to Step 11
11 |

1. Remove the VSS.
2. Measure the resistance in the VSS high and low terminals.

Is the resistance value within the specified value?

530-870ohms

Go to Step 13

Go to Step 12

12 | Replace the Vehicle Speed Sensor (VSS). Is the action complete? | -- | Go to Step 14 | --
13 | Replace the PCM. Is the action complete? | -- | Go to Step 14 | --
14 |

1. Using the scan tool, clear the DTCs.
2. Start the engine and idle at normal operating temperature.
3. Operate the vehicle within the conditions for setting this diagnostic as specified in the supporting text.

Does the scan tool indicate that this diagnostic has ran and passed?

--

Go to Step 15

Go to Step 2

15 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK