P0502
DTC P0502 VEHICLE SPEED SENSOR "A" CIRCUIT LOW INPUTComponent Location:
GENERAL DESCRIPTION
The wheel Speed Sensor (WSS) generates a waveform with a frequency according to the speed of the vehicle. The signal generated by the WSS informs the PCM not only if the vehicle speed is low or high but also is stopped the vehicle or not. The PCM uses this signal to control the fuel injection, ignition timing, transmission/transaxle shift scheduling and torque converter clutch scheduling. Also the WSS signal is used to detect rough road driving condition.
DTC DESCRIPTION
The PCM sets DTC P0502 if PCM detects that wheel Speed Sensor (WSS) signal is less than the threshold value.
DTC Detecting Condition:
Schematic Diagram:
SIGNAL WAVEFORM & DATA
This is the wave form of vehicle sensor when it drives 40 km/h.
- The voltage at point (1) should be below 0.8 V and at point (2) should be above 7 V.
- The frequency of vehicle sensor must increase as the RPM increases.
MONITOR DTC STATUS
This is the inspection procedure to determine whether it is present DTC or memoried one by monitoring the current signal or by using the function of oscilloscope with Hi-scan pro.
1. Connect scantool to Data Link Connector(DLC).
2. Warm up the engine to normal operating temperature.
3. Monitor the "VSS signal" parameter on the scantool.
Service standard
Approximately 40 km/h
NOTE: The data shown above is only for reference and there may be a little difference actually.
4. Is parameter displayed within specifications?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared.Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
NO: Go to "W/Harness Inspection" procedure.
TERMINAL & CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage
3. Has a problem been found?
YES: Repair as necessary and go to "Verification of vehicle Repair" procedure.
NO: Go to "Power Circuit inspection" procedure.
POWER CIRCUIT INSPECTION
1. Ignition "OFF"
2. Disconnect VSS sensor connector.
3. Ignition "ON" & Engine "OFF"
4. Measure voltage between terminal 3 of sensor harness connector and chassis ground.
Specification approximately B+
5. Is measure voltage within Specification?
YES: Go to "Signal circuit inspection" procedure.
NO:
- Open circuit or short circuit to chassis ground between VSS harness connector and battery power circuit.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
NOTE: In case, when the connector of VSS is disconnected, the voltage of terminal 3 is 1 V
- Possible cause: Open circuit or short circuit after I/P- J/BOX fuse(10 A)
SIGNAL CIRCUIT INSPECTION
1. Check for open in harness
1. Ignition "OFF"
2. Disconnect VSS sensor connector.
3. Ignition "ON" & Engine "OFF"
4. Measure voltage between terminal 2 of sensor harness connector and chassis ground.
Specification approximately 5 V
5. Is measure voltage within Specification?
YES: Go to "Check for short to ground in harness" as below.
NO:
- Open or short circuit between VSS harness connector and PCM harness connector.
- Faulty PCM
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
NOTE:
1. In case,when the connector of VSS is disconnected, the voltage of terminal 2 is 0 V
2. The voltage of terminal 2 is about 6.5 - 7.5 V when the VSS connector is disconnected.
- Possible cause: If the terminal 2 voltage of VSS is 0 V, the possible cause is likely to be open or bad PCM.
2. Check for short to ground in harness
when the voltage of VSS terminal 2 is 0 V, the inspection of short circuit is recommended to find open or short circuit of signal line.
1. Ignition "OFF"
2. Disconnect VSS sensor connector and PCM connector.
3. Ignition "ON" & Engine "OFF"
4. Measure resistance between terminal 1 and 2 of sensor harness connector.
Specification : infinite
5. Is measure resistance within Specification?
YES: Go to "Ground Circuit Inspection" procedure.
NO:
- short circuit to chassis ground between VSS harness connector and PCM harness connector.
- short circuit between VSS signal circuit and ground circuit.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
GROUND CIRCUIT INSPECTION
The purpose of checking terminal 2 after disconnecting VSS connector is to check open or short circuit of ground.
1. Ignition "OFF"
2. Disconnect VSS sensor connector.
3. Ignition "ON" & Engine "OFF"
4. Measure voltage or resistance between terminal 1 of sensor harness connector and chassis ground.
Specification : below 0.5 V or below 1 Ohms
5. Is measure voltage or resistance within Specification?
YES: Go to "Component Inspection" procedure.
NO:
- Open circuit between VSS harness connector and Chassis ground.
- Repair as necessary and then go to Verification of Vehicle Repair procedure.
COMPONENT INSPECTION
1. Check PCM
The purpose of checking ECM is to determine whether there is any malfunction of PCM.
1. Ignition "OFF"
2. Connect Scantool and Engine "ON"
3. Select simulation function on scantool.
Specification: If the vehicle speed changes as simulation change,it is OK
4. Is VSS sensor signal value changed according to simulation voltage?
YES: Check VSS for contamination, deterioration, or damage. Clean VSS with suitable cleaner and necessary and let air dry before reinstalling. If problem still exists, Substitute with a know-good VSS and check for proper operation
If the problem is corrected, replace VSS and then go to "Verification of vehicle Repair" procedure
NO: Substitute with a known-good PCM and check for proper operation. If the problem is corrected, replace PCM and then go to "Verification of Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code (DTC) which has been diagnosed.
2. using a Scantool, Clear the DTCs.
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Monitor that all rediness test have been verified "Complete"
5. Are any DTCs present?
YES: Go to the applicable troubleshooting procedure.
NO: System is performing to specification at this time.