GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Cavalier 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 3T40 🢒 DTC P0503

Object Number: 669900 Size: SF
Master Electrical Component List
OBD II Symbol Description Notice

Circuit Description

The vehicle speed sensor (VSS) assembly provides vehicle speed information to the powertrain control module (PCM). The VSS assembly is a permanent magnet generator. The VSS assembly produces an AC voltage as the speed sensor rotor teeth on the transmission governor assembly pass through the sensor's magnetic field. The AC voltage level and the number of pulses increases as the speed of the vehicle increases. The output voltage varies from a minimum of 0.5 volts AC at 25 RPM to more than 100 volts AC at 200 RPM. The PCM converts the pulsing voltage to vehicle speed. The PCM uses the vehicle speed signal to calculate torque converter clutch (TCC) scheduling.

When the PCM detects a loss of vehicle speed with high engine speed in a drive range, then DTC P0503 sets. DTC P0503 is a type B DTC.

Conditions for Running the DTC
    • Engine is running.
    • Time since the last gear select lever change is greater than 6 seconds.
    • Transmission output speed is greater than 500 RPM for 5 seconds.

Conditions for Setting the DTC

Transmission output speed drops more than 1200 RPM in a drive range for 4 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.
    • TCC will not apply.
    • 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 consecutive warm-up cycles without an emission-related fault occurring.

Test Description

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

  1. This step tests for a vehicle speed signal.

    2.

  2. This step tests for the VSS assembly ability to produce an AC voltage.

    3.

  3. This step tests for correct circuit resistance.

    4.

  4. When the VSS assembly is disconnected, the circuit resistance should be infinite.

    5.

  5. This step tests for improper voltage in the circuit.

    6.

  6. This step inspects for possible mechanical problems.

    7.

  7. Replace the PCM only after you have completed the preceding diagnostic steps.

DTC P0503

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls - 2.2 L or Diagnostic System Check - Engine Controls in Engine Controls - 2.4 L

2

  1. Install a Scan Tool .
  2. Turn On the ignition, with the engine OFF.

    3. Important: Before clearing the DTC, use the Scan Tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.

    5. Notice: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel.

  5. Raise and support the drive wheels.
  6. Start and idle the engine.
  7. Place the transmission in DRIVE.

With the drive wheels rotating, does the Scan Tool transmission output speed increase when the wheel speed increases?

--

Go to Intermittent Conditions in Engine Controls - 2.2 L or Intermittent Conditions in Engine Controls - 2.4 L

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the PCM connectors C1 and C2.
  3. Using the J 35616-A connector test adapter kit, connect the J 39200 digital multimeter (DMM) between PCM terminals C1-64 and C2-61.
  4. Select AC volts.
  5. Turn ON the ignition, with the engine OFF.
  6. Rotate the right front drive wheel by hand.
  7. Observe the voltmeter display.

Can a voltage value greater than the specified amount be obtained?

0.5 V AC

Go to Step 14

Go to Step 4

4

  1. Leave the J 39200 DMM test leads connected.
  2. Measure circuit resistance.

Is the circuit resistance within the specified range?

139-376 ohms

Go to Step 8

Go to Step 5

5

Is the circuit resistance greater than the specified value?

376 ohms

Go to Step 11

Go to Step 6

6

  1. Leave the J 39200 DMM test leads connected.
  2. Disconnect the VSS assembly connector at the transmission.

Is the circuit resistance less than specified?

139 ohms

Go to Step 7

Go to Step 13

7

Test the high signal circuit (CKT 400) and the low signal circuit (CKT 401) of the VSS for being shorted together.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

--

8

Test the high signal circuit (CKT 400) of the VSS for a short to ground.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 9

9

  1. Reconnect PCM connectors C1 and C2.
  2. Using the J 39200 DMM, connect the test leads to terminals A and B of the VSS assembly connector end.
  3. Select DC volts.
  4. Turn ON the ignition, with the engine OFF.

Does the DMM display system voltage?

--

Go to Step 10

Go to Step 12

10

Test the high signal circuit (CKT 400) of the VSS for a short to power.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

--

11

Test the high signal circuit (CKT 400) and the low signal circuit (CKT 401) for an open.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

12

  1. Remove the VSS assembly. Refer to Vehicle Speed Sensor Replacement .
  2. Inspect the VSS assembly and the transmission for the following:
    3. • Loose VSS assembly mounting
    • VSS assembly damage
    • Excessive VSS assembly to speed sensor rotor gap
    • Incorrect speed sensor rotor alignment
    • Speed sensor rotor damage
  3. Repair any of the conditions as necessary.

Refer to Transmission Overhaul in the 3T40-E Section of the Transmission Unit Repair Manual.

Did you complete the repair?

--

Go to Step 15

--

13

Replace the VSS assembly.

Refer to Vehicle Speed Sensor Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM.

Refer to Powertrain Control Module Replacement in Engine Controls - 2.2 L or Powertrain Control Module Replacement in Engine Controls - 2.4 L.

Did you complete the replacement?

--

Go to Step 15

--

15

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle in drive range with the transmission output speed greater than 500 RPM for 2 seconds.
  4. Select Specific DTC.
  5. Enter DTC P0503.

Has the test run and passed?

--

System OK

Go to Step 1