The vehicle speed sensor (VSS) is a permanent magnet generator attached to the transmission case. The final drive assembly has a toothed wheel, VSS rotor. As the final drive assembly rotates, an AC voltage is induced and transmitted to the powertrain control module (PCM). The PCM converts the AC voltage into a digital signal. The PCM uses vehicle speed to determine shift timing, torque converter clutch apply and release and gear ratio.
If 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.
• | No MAF DTCs P0101, P0102 or P0103. |
• | No MAP DTCs P0106, P0107 or P0108. |
• | No TP DTCs P0121, P0122 or P0123. |
• | No VSS DTC P0502. |
• | No AT ISS DTCs P0716 or P0717. |
• | No IMS DTCs P1820, P1822, P1823, or P1825. |
• | No 1-2 shift solenoid valve electrical DTC P0974. |
• | The engine run time is greater than 5 seconds. |
• | The transmission is not in PARK or NEUTRAL. |
• | The time since the gear select lever change is greater than 6 seconds. |
• | The transmission input shaft speed has not changed by 500 RPM or greater for at least 4.8 seconds. |
• | LD8: The transmission output shaft speed is greater than 1,286 RPM and has not increased by 500 RPM or greater for at least 2 seconds. |
• | L37: The transmission output shaft speed is greater than 1,078 RPM and has not increased by 500 RPM or greater for at least 2 seconds. |
• | LD8: The transmission output shaft speed drops 1,125 RPM or greater for at least 1 second. |
• | L37: The transmission output shaft speed drops 943 RPM or greater for at least 1 second. |
• | 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 adaptive functions. |
• | The PCM calculates vehicle speed from the automatic transmission input, shaft, speed sensor and commanded gear. |
• | The PCM applies the TCC in 3rd gear when in Hot Mode. |
• | 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. |
• | 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. |
The numbers below refer to the step numbers on the diagnostic table.
This step tests for DTCs and for a vehicle speed signal. It is important to record Freeze Frame and Failure Record information before proceeding further.
This step tests for a resistance value greater than 1,911 ohms which would indicate an open in the high signal circuit, the low signal circuit or the VSS.
Step | Action | Values | Yes | No | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 4.6L | ||||||||||
Important: Before clearing the DTC, use the scan tool to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM. 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. With the drive wheels rotating, does the Transmission OSS RPM increase when the wheel speed increases? | -- | Go to Intermittent Conditions in Engine Controls - 4.6L | Go to Step 3 | |||||||||||
3 |
Important: Place the gear select lever in the Neutral position before rotating the drive wheel. Can a voltage greater than the specified value be obtained? | 0.5 V AC | Go to Step 14 | Go to Step 4 | ||||||||||
4 |
Does the resistance measure within the specified range? | 1,260-1,911 ohms | Go to Step 8 | Go to Step 5 | ||||||||||
Is the circuit resistance greater than the specified value? | 1,911 ohms | Go to Step 11 | Go to Step 6 | |||||||||||
6 |
Does the resistance measure less than the specified value? | 1,260 ohms | Go to Step 7 | Go to Step 13 | ||||||||||
7 | Test the high signal circuit and the low signal circuit 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 of the VSS for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 9 | ||||||||||
9 |
Does the DMM display system voltage? | -- | Go to Step 10 | Go to Step 12 | ||||||||||
10 | Test the high signal circuit of the VSS for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | -- | ||||||||||
11 |
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 15 | Go to Step 13 | ||||||||||
12 |
Refer to Vehicle Speed Sensor Replacement .
Refer to Differential Carrier and Housing Removal in the 4T80-E section of the Transmission Unit Repair Manual. Did you complete the repair? | -- | Go to Step 15 | -- | ||||||||||
13 | Replace the VSS. 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 - 4.6L. Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||||||
15 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 16 | Go to Step 2 | ||||||||||
16 | With the scan tool, observe the stored information, capture info, and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 4.6L | System OK |