DTC P0502 3.8L
Circuit Description
The vehicle speed sensor (VSS) system is a pulse generator consisting of a speed sensor assembly, located in the case extension, and a toothed vehicle speed sensor reluctor wheel, which is pressed onto the final drive carrier assembly. As the vehicle drives forward, the vehicle speed sensor reluctor wheel rotates. This rotation produces a variable AC signal in the pickup coil that is proportional to vehicle speed. The PCM uses this signal in order to calculate vehicle speed, shift timing and gear ratios.
If the PCM detects a low vehicle speed with a high engine speed while in a drive range, then DTC P0502 sets. DTC P0502 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Voltage
Conditions for Running the DTC
| • | No MAP sensor DTC P0107 or P0108. |
| • | No ISS DTC P0716 or P0717. |
| • | The engine speed is greater than 500 RPM for 5 seconds and not in fuel cut off. |
| • | The TP angle is 12 percent or greater. |
| • | The TFT is 0°C (32°F) or more. |
| • | The engine torque is 68-407 N·m (50-300 lb ft). |
| • | The input shaft speed is 1,500 RPM or greater. |
| • | The TCC slip speed is 0 RPM or more. |
Conditions for Setting the DTC
The output shaft speed is 150 RPM or less for 5 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. |
| • | The PCM inhibits TAP shift operation, if equipped. |
| • | The PCM freezes transmission adaptive functions. |
| • | The PCM calculates vehicle speed from the AT input shaft speed sensor for shift timing. |
| • | 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 P0502 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 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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the ability of the VSS to produce an AC voltage. This step also verifies the integrity of the wiring to the PCM.
-
This step tests the VSS circuit for correct resistance.
Step | Action | Value(s) | 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. Using the Clear DTC Information function will erase the stored 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. Does the Transmission OSS RPM increase when wheel speed increases? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||||||||||
Does the voltage measure greater than the specified value? | 0.4 V AC | Go to Step 8 | Go to Step 4 | |||||||||||||
Is the circuit resistance within the specified range? | 1,650-3,180 ohms | Go to Step 9 | Go to Step 5 | |||||||||||||
5 | Is the circuit resistance greater than the specified value? | 3,180 ohms | Go to Step 11 | Go to Step 6 | ||||||||||||
6 |
Are the signal and ground circuits shorted together? | -- | Go to Step 7 | Go to Step 14 | ||||||||||||
7 | Repair the short between the VSS high signal circuit and the VSS low signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 16 | -- | ||||||||||||
8 | Test the high signal circuit of the VSS for a short to ground between the PCM and the VSS. Refer to Testing for Short to Ground and Wiring Repairs Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 | ||||||||||||
9 |
Does the DMM display greater than the specified voltage? | 1.0 V | Go to Step 10 | Go to Step 13 | ||||||||||||
10 | Repair the short to voltage in the VSS high signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 16 | -- | ||||||||||||
11 | Test the high signal circuit of the VSS for an open between the PCM and the VSS. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 12 | ||||||||||||
12 | Test the low signal circuit of the VSS for an open between the PCM and the VSS. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||||||||
13 |
Refer to Vehicle Speed Sensor Replacement .
Refer to Differential Carrier Inspection. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||||||||
14 | Replace the VSS. Refer to Vehicle Speed Sensor Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||||||
15 | Replace the PCM. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||||||
16 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 17 | Go to Step 2 | ||||||||||||
17 | With a 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 |
