P0503

DTC P0503

Schematic:

Circuit Description
The Automatic Transmission Output, Shaft, Speed Sensor (AT OSS) provides vehicle speed information to the PCM. The AT OSS is a permanent magnet generator mounted to the transmission case. The AT OSS produces an AC voltage as the transmission speed sensor rotor teeth pass through the sensor's magnetic field. The AC voltage level increases as the speed of the vehicle increases. The PCM converts the AC voltage into a digital signal. The PCM uses the vehicle speed signal to determine shift timing, Torque Converter Clutch (TCC) apply, TCC release, and gear ratio calculations.
When the PCM detects a loss of vehicle speed while the vehicle is in motion, then DTC P0503 sets. DTC P0503 is a type B DTC.

Conditions for Running the DTC
- No TFP manual valve position switch DTC P1810.
- The engine is running.
- The time since the gear select lever change is greater than 6 seconds.
- An increase in output speed of 250 RPM or greater has not occurred for greater than 5 seconds.

Conditions for Setting the DTC
Output speed drops greater than 1,200 RPM for 3 seconds.

Action Taken When the DTC Sets
- The PCM illuminates the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
- The PCM commands maximum line pressure.
- The PCM freezes transmission adapt functions.
- The PCM calculates output speed from input speed, engine speed, and commanded gear.
- The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
- The PCM stores DTC, P0503 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC
- The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
- A scan tool can clear the MIL/DTC.
- The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
- The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

Test Description

Steps 1-8:

Steps 9-15:

The numbers below refer to the step numbers on the diagnostic table.
3. This step tests the ability of the AT OSS to produce an AC voltage. This step also verifies the integrity of the wiring to the PCM.
4. This step tests the AT OSS circuit for correct resistance.