Engine Control System

DTC P0503 Vehicle Speed Sensor "A" Intermittent/Erratic/High

CIRCUIT DESCRIPTION

DTC Detection Condition:

The vehicle speed sensor detects the rotation speed of the transmission output shaft and sends signals to the ECM. The ECM determines the vehicle speed based on these signals. An AC voltage is generated in the vehicle speed sensor coil when the rotor mounted on the output shaft rotates, and then this voltage is sent to the ECM.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Manual transmission:
The ECM assumes that the vehicle is driven when the calculated engine load is large. If there is no signal from the vehicle speed sensor when the vehicle is driven, the ECM interprets this as a malfunction in the vehicle speed sensor circuit. The ECM illuminates the MIL and sets the DTC.

Automatic transmission:
The ECM assumes that the vehicle is driven when the engine RPM is more than 2,250 rpm and the park/neutral position switch was turned to OFF (for 30 seconds). If there is no signal from the vehicle speed sensor when the vehicle is driven, the ECM interprets this as a malfunction in the vehicle speed sensor circuit. The ECM illuminates the MIL and sets the DTC.

Wiring Diagram:

Step 1:

Step 2 - 3:

Step 4:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

CHECK FOR INTERMITTENT PROBLEMS

HINT:
Hand-held tester only:
Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect with the hand-held tester when the ECM is in check mode. In check mode, the ECM uses 1trip detection logic, which is more sensitive to malfunctions than normal mode (default) that uses 2trip detection logic.

a. Clear DTCs.
b. Switch the ECM from normal mode to check mode using a hand-held tester.
c. Perform a simulation test.
d. Check and wiggle the harness(es), the connector(s) and terminal(s).