The Wheel Speed Sensor (WSS) generates a waveform with a frequency proportional to the speed of the vehicle. The signal generated by the WSS informs the ECM not only if the vehicle speed is low or high but also if the vehicle is or is not moving. The ECM uses this signal to control the fuel injection, ignition timing, transaxle shift scheduling and torque converter clutch scheduling. The WSS signal is also used to detect rough road conditions.
Checking vehicle speed signal every from ABS(or ESC) control every 30 sec. under detecting condition, if an signal is in the detecting condition for more than 20 sec., ECM sets P2159.
Item
Detecting Condition
Possible cause
DTC Strategy
Detects the lack of vehicle speed signal
Poor connection
Open or short in harness
Wheel speed sensor(FR)
ABS or ESC control unit
ECM
Enable
Conditions
Case 1
Engine Running
No VSS disabling malfunction present
No TPS fault present
No MAP fault present
11V < Ignition Voltage < 16V
Engine Coolant Temperature > 60?(140?)
MAP > 55kPa
25% = TPS = 60%
1200rpm = Engine Speed = 4000rpm
Vehicle Speed derived from transmission
= 10KPH(6.2MPH)
Case 2
MAP < 32kPa
TPS < 1%
1800rpm = Engine Speed = 6000rpm
Transmission in gear
Threshold
value
Vehicle Speed = 10kph
Vehicle Speed < 5kph
Delta Engine Speed = 100rpm
Diagnosis Time
Continuous (More than 20 seconds failure for every 30 seconds test )
MIL On Condition
3 Driving Cycles
Fig. 1) Normal data & waveforms of VSS (from ABS,ESC(ESP) ECU) when vehicle speed is 6km/h.
Fig. 2) Normal data & waveforms of VSS (from ABS,ESC(ESP) ECU) when vehicle speed is 25km/h.