Vehicle/Wheel Speed Sensors - Diagnostics
Group: ENGINE ELECTRICALNumber: 00-36-011
Date: OCTOBER, 2000
Model: ALL 2001 MY
Subject:
VEHICLE SPEED SENSOR (VSS) AND
RIGHT FRONT WHEEL SPEED SENSOR (RF-WSS)
DIAGNOSIS
DESCRIPTION:
This bulletin explains the function of the Vehicle Speed Sensor (VSS) and Right Front Wheel Speed Sensor (RF-WSS) on current Hyundai models and how they relate to Diagnostic Trouble Codes (DTC). It also helps diagnose conditions related to these sensors.
KEY information:
The same DTC, P0500 (Vehicle Speed Sensor Fault), can be set by the VSS or the RF-WSS, depending on the model.
The table listed in this TSB can be used to determine which sensor is pertinent to which model vehicle when working on a DTC for the vehicle speed sensor.
VEHICLE SPEED SENSOR (VSS):
The VSS on current Hyundai vehicles is one of two types:
1. Electrical sensor (either magnetic or Hall-type sensor) mounted directly on the transmission. This sensor is driven by a gear on the transaxles final drive assembly. All current model vehicles use this type of sensor, except for the Accent.
2. Electrical sensor (reed switch type) mounted to the speedometer head unit. This sensor is driven by magnets mounted on the speedometer shaft, which is driven by the speedometer cable.
The main functions of the VSS are to:
1. Send a signal to the speedometer -- input to the speedometer (except for vehicles equipped with a speedometer cable and reed switch VSS).
2. Send a signal to the ECM/TCM (this signal is typically used by the ECM/TCM for diagnostic purposes).
RIGHT FRONT WHEEL SPEED SENSOR (RF-WSS):
Some Hyundai Vehicles incorporate a sensor on the right front hub. This sensor reads a "tone-wheel" mounted on the right front axle assembly. The sensor and tone-wheel function very similarly to the crankshaft position sensor. The main function of this sensor is to send a signal directly to the ECM.
When driving over a very rough road, the engine will experience a sharply varying load, transferred from the wheels to the crankshaft, which may incorrectly appear to be an engine misfire to the ECM misfire diagnostic logic (based on the analysis of the crankshaft position sensor signal). The RF-WSS is used to minimize inaccurate diagnoses that an engine misfire has occurred.
The RF-WSS signal is used to determine if the vehicle is going over a rough road. If the ECM determines that the vehicle is going over a rough road, based on the "roughness" of the signal from the RF-WSS, the misfire diagnostics will be suspended until the driving conditions have changed.
VEHICLES EQUIPPED WITH ANTI-LOCK BRAKES (ABS) OR ABS/TRACTION CONTROL SYSTEM (TCS) WHICH USE THE RF-WSS TO DETERMINE ROUGH ROAD CONDITION:
On vehicles equipped with ABS/(TCS), the RF-WSS sends a signal to the ABS Module (computer). If the vehicle uses the RF-WSS to determine rough road condition (such as the 2001 Elantra), the ABS Module sends a signal to the ECM for use in determining the rough road condition.
The RF-WSS and the "tone-wheel" on the right front axle are the same components on ABS and Non-ABS equipped vehicles.
A malfunction of the RF-WSS will result in:
1. The ABS light being turned ON.
2. Diagnostic Trouble Code C1203 ("RF Wheel Sensor Open or Short") stored in the ABS Module.
NOTE:
All XG300 vehicles are equipped with ABS.
APPLICATION:
All current Hyundai vehicles are equipped with a VSS, however, not all are equipped with a RF-WSS. Vehicles which are not equipped with a RF-WSS use other means to determine when the vehicle is traveling over a rough road (for example, the Tiburon uses a rough road sensor mounted to the left front shock tower).
The table shows the application on the latest model vehicles.
DIAGNOSIS of the VSS and RF-WSS:
There are three main symptoms of a VSS or RF-WSS related fault:
1. The Check Engine Light is ON and a Diagnostic Trouble Code (DTC) related to the VSS or RF-WSS is stored in the ECM/TCM/ABS Module.
2. The speedometer is inoperative.
3. The Vehicle Speed display on the Hi-Scan Pro (under the Engine current data menu) shows no output (display shows 0 mph while the vehicle is moving).
The table in this bulletin shown, shows the results of a non-functioning sensor.
Diagnostic Trouble Codes (DTC):
If a vehicle has a VSS related DTC stored in the ECM/TCM, it is very important to use the table to determine which sensor is related to the DTC.
DTCs related to either the VSS or RF-WSS will set a P0500 or P0501 code (on vehicles without ABS/TCS). The code description on Hi-Scan Pro typically reads "Vehicle Speed Sensor -- Abnormal" and makes no mention of the Right Front Wheel Speed Sensor, even when the RF-WSS or it's related circuitry have caused the DTC to be set.
EXAMPLE:
On the 2.4L 14 Sonata, the DTC P0500 (the Hi-Scan Pro description is "Vehicle Speed Sensor") indicates a condition with the VSS mounted on the transmission or related circuitry.
On the 2.5L V6 Sonata, the DTC P0500 (the Hi-Scan Pro description is again "Vehicle Speed Sensor") indicates a condition with the RF-WSS mounted on the right front hub or related circuitry.
Thus, for the Sonata, the same DTC (P0500) on different engine options (2.4L versus 2.5L) relate to a different sensor (one mounted on the transmission and the other mounted to the right front hub).
RECOMMENDATIONS:
^ Because the code alone does not pinpoint which sensor/circuit may be related to the code, refer to the table on the following page when working on a VSS related code.
^ The condition can be verified by checking the operation of the speedometer and/ or the vehicle speed readout on the Hi-Scan Pro.
^ Once the correct sensor/circuit has been determined, diagnose the condition by checking the integrity of the circuit and the function of the sensor.
DIAGNOSTIC PROCEDURE EXAMPLE:
1. The Check Engine Light is ON.
VEHICLE: 2001 Elantra.
2. A VSS related DTC is stored in the ECM (P0500 or P0501).
EXAMPLE: DTC P0501 ("Vehicle Speed Sensor -- Abnormal�) stored in ECM.
3. Using the table, determine which sensor is related to the DTC.
EXAMPLE: The table indicates that the RF-WSS is related to the code P0501.
4. Diagnose the related electrical circuit and the sensor for proper function.
EXAMPLE: Check that the RF-WSS circuit and sensor are functioning properly. Make sure that the "tone-wheel" on the RF-axle is not damaged.