P0503

Wiring Diagram:

CIRCUIT DESCRIPTION

The Output Shaft Speed Sensor (OSS Sensor), which is a Permanent Magnet (PM) generator, provides the vehicle speed information to the Vehicle Control Module (VCM). The PM generator produces a pulsing AC voltage as the transmission speed sensors rotor teeth pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The VCM then converts the pulsing voltage to a digital signal for vehicle speed. The vehicle speed is used for engine and transmission calculations.

If the VCM detects a low vehicle speed and there is a high engine speed in a drive gear range, DTC P0503 sets. DTC P0503 is a type D DTC. For California emissions, DTC P0503 is a type B DTC.

CONDITIONS FOR SETTING THE DTC

^ No Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) DTC P1810.

^ No TFP Val. Position Sw. changes in less than 10 seconds.

^ The A/T ISS is greater than 1500 RPM.

^ The gear range is not Park or Neutral.

^ The engine is running more than 475 RPM for 7 seconds.

^ No VSS increase greater than 250 RPM within 2 seconds.

^ The OSS RPM has dropped more than 1000 RPM for at least 4 seconds.


ACTION TAKEN WHEN THE DTC SETS

^ For California emissions, the VCM illuminates the Malfunction Indicator Lamp (MIL).

^ The VCM commands maximum line pressure.

^ The VCM freezes the shift adapts.

^ The VCM defaults a calculated output speed value by using the ISS values.

^ DTC P0503 is stored in the VCM history.


CONDITIONS FOR CLEARING THE MIL/DTC

^ For California emissions, the VCM turns off the MIL after three consecutive trips without a failure reported.

^ A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.

^ The VCM cancels the DTC default actions when the fault no longer exists and the ignition is cycled OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS

^ DTC P0503 sets when the VCM detects an OSS loss.

^ Inspect the wiring at the VCM, the OSS Sensor connector and all other circuit connecting points for the following conditions:

- A bent terminal

- A backed out terminal

- A damaged terminal

- Poor terminal tension

- A chafed wire

- A broken wire inside the insulation.

- Moisture intrusion

- Corrosion

^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.

^ The vehicle may need to be driven to duplicate the intermittent condition.

^ First diagnose and clear any engine DTCs or TP Sensor codes. Then inspect for any transmission DTCs that may have reset.

TEST DESCRIPTION

The numbers below refer to the step numbers on the diagnostic table.

3. This step tests the integrity of the OSS Sensor.

5. This step tests for voltage in the 822 low circuit.

7. This step tests the 5-volt and ground circuit of the OSS sensor circuit.

13. This step tests the OSS sensor and the circuit.