Circuit Description
The automatic transmission output shaft speed (AT OSS) sensor is a three-wire magnetic pick-up sensor that is mounted externally to the transmission. The OSS utilizes the gear teeth, located on the output shaft, to generate a voltage signal of varying frequency that corresponds to the rotational speed of the output shaft. The OSS signal is sent to the powertrain control module (PCM) and is used to calculate output shaft speed and vehicle speed. Simultaneously, the automatic transmission input shaft speed (AT ISS) sensor signal is used to calculate the input shaft speed and the vehicle speed. The PCM compares the vehicle speed calculated from both speed sensors and uses this comparison for diagnosis of the speed sensors.
If the PCM detects the OSS calculated vehicle speed is 6 times or greater than the ISS calculated vehicle speed, DTC P0501 sets. DTC P0501 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0501 Vehicle Speed Sensor (VSS) Performance
Conditions for Running the DTC
| • | No TR Switch DTCs P0705 or P0706. |
| • | No AT ISS DTCs P0716 or P0717. |
| • | No Clutch PC Solenoid 1 DTCs P0962 or P0963. |
| • | No Clutch PC Solenoid 2 DTCs P0966 or P0967. |
| • | No SS 1 DTCs P0973 or P0974. |
| • | No SS 2 DTCs P0976 or P0977. |
| • | No SS 3 DTCs P0979 or P0980. |
| • | No TCC PC Solenoid DTCs P2763 or P2764. |
| • | No TCC Enable Solenoid DTCs P2769 or P2770. |
| • | The ignition voltage is greater than 11 volts. |
| • | The engine speed is 500 RPM or greater for 5 seconds. |
| • | The vehicle speed is greater than 20 km/h (13 mph). |
| • | The commanded gear is greater than 1st. |
| • | The selected range is D, I, or L. |
| • | The transmission is not shifting. |
Conditions for Setting the DTC
The ratio of the vehicle speed calculated from the OSS signal, divided by the vehicle speed calculated from the ISS signal is 6.0 or greater for 10 seconds.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL). |
| • | The PCM limits the commanded gears to 2nd and 3rd 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 P0501 in PCM history. |
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 cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Inspect the connectors at the PCM, the OSS, and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections . |
| • | Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents . |
| • | Inspect for a disconnected output shaft speed sensor connector. |
| • | Inspect for an open or shorted output shaft speed sensor wire. |
| • | Inspect for a faulty output shaft sensor. |
| • | Inspect for an internal fault of PCM. |
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||
2 |
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. 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. Does the scan tool indicate Transmission OSS parameter increasing when wheel speed increases? | -- | Go to Step 3 | |||||||||
3 |
Does the voltage measure near the specified value? | 5 V | Go to Step 4 | Go to Step 7 | ||||||||
4 | Measure the voltage from the OSS 5 volt reference circuit to the OSS low reference circuit. Does the voltage measure near the specified value? | 5 V | Go to Step 5 | Go to Step 8 | ||||||||
5 | Measure the voltage from the OSS high signal circuit to the OSS low reference circuit. Does the voltage measure near the specified value? | 5 V | Go to Step 9 | Go to Step 6 | ||||||||
6 | Test the OSS high signal circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||||||
7 |
Important: The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Power Distribution Schematics for complete circuit distribution. Test the OSS 5 volt reference circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||||||
8 | Test the OSS low reference circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||||||
9 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||||||
10 | Replace the OSS. Refer to Output Speed Sensor Replacement . Did you complete the repair? | -- | Go to Step 12 | -- | ||||||||
11 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the repair? | -- | Go to Step 12 | -- | ||||||||
12 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | Go to Step 13 | Go to Step 2 | ||||||||
13 | 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? | -- | System OK |
