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Makes 🢒 Pontiac 🢒 1997 🢒 Firebird 🢒 DTC 🢒 DTC P0503 Vehicle Speed Sensor (VSS) Circuit Intermittent

DTC P0503 Vehicle Speed Sensor (VSS) Circuit Intermittent 3.8L, VIN K Only


Object Number: 42294 Size: SF
Handling ESD Sensitive Parts Notice
OBD II Symbol Description Notice
Automatic Transmission Components VIN K

Circuit Description

The Vehicle Speed Sensor (VSS) provides vehicle speed information to the Powertrain Control Module (PCM). The VSS is a Permanent Magnet (PM) motor. The VSS produces a pulsing AC voltage. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The PCM converts the voltage pulses to vehicle speed. A scan tool can display the calculated vehicle speed.

If the PCM detects an unrealistically large drop in the output speed in two consecutive ignition cycles, then DTC P0503 sets. DTC P0503 is a type B DTC.

Conditions for Setting the DTC

DTC P0503 sets if the following conditions occur once per ignition cycle, two consecutive times.

    • No TFP Manual Valve Position Switch DTC P1810.
    • The engine speed is greater than 400 RPM for five seconds and not in fuel cutoff.
    • The time since the last gear range change is greater than six seconds.
    • The transmission output speed does not rise by 500 RPM within six seconds.
    • The transmission output speed drops by greater than 1600 RPM in Park/Neutral.
    • The transmission output speed drops by greater than 1300 RPM and is not in Park/Neutral.
    • All conditions are met for 3 seconds.

Action Taken When the DTC Sets
    • The PCM commands a soft landing to second gear.
    • The PCM inhibits TCC engagement.
    • The PCM commands maximum line pressure.
    • The PCM inhibits fourth gear in Hot Mode.
    • The PCM freezes shift adapts from being updated.
    • The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
    • A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
    • The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • An incorrect VSS calibration may set DTC P0503. Refer to Service Bulletins to ensure that the calibration is the most current.
    • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    • Inspect the wiring for poor electrical connections at the PCM.
    • Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following problems:
       - A bent terminal
       - A backed out terminal
       - A damaged terminal
       - Poor terminal tension
       - A chafed wire
       - A broken wire inside the insulation
    • Test circuits 400 and 401 for Electromagnetic Interferences (EMI) induced by a wiring harness incorrectly routed near the spark plug wires.
    • Inspect for a damaged VSS.
    • Inspect for damaged transmission rotor teeth.
    • Ensure that the VSS is correctly aligned and torqued securely to the transmission case.

Test Description

An example test description follows:

  1. This step verifies the integrity of the VSS.

    2.

  2. This step tests the resistance of the VSS.

    3.

  3. This step verifies the integrity of the VSS circuit.

DTC P0503 Vehicle Speed Sensor (VSS)-Intermittent

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check , Section 6.

2
  1. Install the Scan Tool ®.
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

  3. Record the Freeze Frame and Failure Records.
  4. Raise and support the drive wheels.
  5. Start the engine.
  6. Disable the traction control system, if equipped.
  7. Place the transmission in any drive range.
  8. Observe the Transmission Output Speed Sensor (Trans. OSS) value displayed on the scan tool.

With the drive wheels rotating, does the Trans. OSS RPM increase as the drive wheel speed increases?

--

Go to Step 3

Go to Step 5

3

Verify the PCM's calibration ID. Use the scan tool.

Refer to Service Bulletins for the current calibration ID.

Does the Powertrain Control Module's calibration identification number match the Service Bulletin's calibration identification number?

--

Go to Step 5

Go to Step 4

4

Update the Powertrain Control Module (PCM) with the current calibration.

Refer to Powertrain Control Module Replacement/Programming .

Is the PCM's calibration updated?

--

Go to Step 12

--

5
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the wiring harness connector from the Vehicle Speed Sensor (VSS).
  3. Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM between VSS terminals A and B.
  4. Select the AC Volts option on the J 39200 DMM.
  5. Be sure that the drive shaft is turning by rotating the drive wheels.

Is the measured voltage greater than the specified value?

0.5 volts

Go to Step 9

Go to Step 6

6
  1. Connect the J 39200 DMM between VSS terminals A and B. Use the J 35616-A Connector Test Adapter Kit.
  2. Select the Ohms option on the J 39200 DMM.

Is the measured resistance within the specified range?

1470-2820 ohms

Go to Step 7

Go to Step 8

7
  1. Remove the VSS from the automatic transmission.
  2. Inspect the Output Shaft Speed Sensor rotor for damage or misalignment.

Did you find and correct a problem?

--

Go to Step 12

Go to Step 8

8

Replace the VSS.

Refer to Vehicle Speed Sensor, in On-Vehicle Service.

Is the replacement complete?

--

Go to Step 12

--

9
  1. Inspect circuit 400 (YEL) for the following problems:
    2. • An open circuit
    • A short to ground
    • A short to positive battery voltage
  2. Inspect circuit 401 (PPL) for the following problems:
    3. • An open circuit
    • A short to ground
    • A short to positive battery voltage
  3. Inspect circuits 400 (YEL) and 401 (PPL) for a short together.

Refer to Troubleshooting Procedures, Section 8.

Did you find and correct a problem?

--

Go to Step 12

Go to Step 10

10
  1. Disconnect the C1 (Blue) connector from the Powertrain Control Module (PCM).
  2. Inspect the PCM connector terminals for the following problems:
    3. • Damaged connector pins
    • Backed-out connector pins
    • Weak terminal tension

Did you find and correct a problem?

--

Go to Step 12

Go to Step 11

11

Replace the PCM.

Refer to Powertrain Control Module Replacement/Programming , Section 6.

Is the replacement complete?

--

Go to Step 12

--

12

In order to verify your repair, perform the following procedure:

  1. Select DTC on the scan tool.
  2. Select Clear Info on the scan tool.
  3. Operate the vehicle so that the transmission output speed is greater than 600 RPM for 3 seconds and does not drop by more than 500 RPM.
  4. Select Specific DTC on the scan tool.
  5. Enter DTC P0503.

Has the test run and passed?

--

System OK

Begin diagnosis again. Go to Step 1