Fuel System > Engine Control System > P0501 Vehicle Speed Sensor \

General Description

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 PCM not only if the vehicle speed is low or high but also if the vehicle is or is not moving. The PCM 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.

DTC Description

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., PCM sets P0501. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

DTC Detecting Condition

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

•

PCM

Enable
Conditions

Case 1(Power)

•	Engine Running

•	No VSS disabling malfunction present

•	No TPS fault present

•	No MAP fault present

•	11V< Ignition Voltage< 16V

•	Engine Coolant Temperature >60°C (140°F)

•	MAP >55kPa

•	25% ≤ TPS ≤ 60%

•	1200rpm ≤ Engine Speed ≤ 4000rpm

•	Vehicle Speed derived from transmission ≥ 10 kph(6.2 mph)

Case 2(Decel)

•	Engine Running

•	No VSS disabling malfunction present

•	No TPS fault present

•	No MAP fault present

•	11V< Ignition Voltage< 16V

•	Engine Coolant Temperature >60°C (140°F)

•	MAP< 32kPa

•

TPS< 1%

•	1800rpm ≤ Engine Speed ≤ 6000rpm

•	Transmission in gear

Thresh
old
value

Case 1(Power)

•	Vehicle Speed ≤ 10kph

Case 2(Decel)

•	Vehicle Speed< 5kph

•	Delta Engine Speed ≥ 100rpm

Diagnosis Time

•	Continuous (More than 20 seconds failure for every 30 seconds test )

MIL On Condition

•	2 driving cycles

Schematic Diagram

Monitor DTC Status

Check DTC Status

(1)	Connect scantool to Data Link Connector(DLC).

(2)

IG "ON".

(3)	Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.

(4)	Read "DTC Status" parameter.

(5)

Is parameter displayed "Present fault"?

	▶ Go to "Terminal and connector inspection" procedure.
	▶ 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, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

Terminal And Connector Inspection

1.	Many malfunctions in the electrical system are caused by poor harness and terminal condition. 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.

Has a problem been found?

	▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
	▶ Go to " Signal Circuit Inspection " procedure.

Signal Circuit Inspection

■ Check short to ground in harness

IG "OFF"

2.	Disconnect PCM connector and ABS(ESC) control module connector.

Measure resistance between vehicle speed input signal terminal of PCM harness connector and chassis ground.

Specification : Infinite

Is the measured resistance within specifications?

	▶ Go to "Check open in harness" as follows.
	▶ Repair short to ground in harness, and go to "Verification of Vehicle Repair" procedure.

■ Check for open in harness

1.	Ignition "OFF"

2.	Disconnect PCM connector and ABS(ESC) control module connector.

Measure resistance between vehicle speed input signal terminal of PCM harness connector and wheel speed sensor output signal terminal of ABS(ESC) control module harness connector.

Specification : Approx. below 1Ω

Is the measured resistance within specifications?

	▶ Go to " Check wheel speed sensor " procedure.
	▶ Check open in harenss. ▶ Repair or replace as necessary and then, go to " Verification of Vehicle Repair" procedure.

■ Check wheel speed sensor

IG "OFF"

2.	Check open or short in wheel speed sensor (Refer to "C1203 Wheel speed sensor front-RH open/short")

Is the wheel speed sensor normal?

	▶ Substitute with a known - good PCM/ ABS(ESC) control unit and check for proper operation. If the problem is corrected, replace PCM/ ABS(ESC) control unit and go to "Verification of Vehicle Repair" procedure.
	▶ Repair or replace it as necessary. ▶ And then go to " Verification of Vehicle Repair" procedure.

There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. After testing PCM on the vehicle, use this function to reuse the PCM on the others.

Verification Of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.

1.	Connect scantool and select "DTC" button.

2.	Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions

3.	Read "DTC Status" parameter

Is parameter displayed "History(Not Present) fault"?

	▶ System performing to specification at this time. Clear the DTC
	▶ Go to the applicable troubleshooting procedure.