OBD-II Code P0502 - VSS Low Input
 

Does anyone know how to troubleshoot this Vehicle Speed Sensor problem?

I replaced the VSS, but still get the code.

Re: OBD-II Code P0502 - VSS Low Input
 

<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=1582045&pubCellSyskey=7025&pu bObjSyskey=1582045&from=sm&cellId=7025#tab8-1582045"> DTC P0502

Step
Action
Values
Yes
No
1
Did you perform the Diagnostic System Check - Vehicle?
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Go to Step 2
Go to Diagnostic System Check - Vehicle
2

1. <LI type=1>Install a scan tool. <LI type=1>Turn ON the ignition, with the engine OFF. 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.
   <LI type=1>Record the DTC Freeze Frame and Failure Records. <LI type=1>Clear the DTC. <LI type=1>Raise and support the rear axle assembly. <LI type=1>Start the engine.
2. Place the transmission in any drive range.

With the drive wheels rotating, does the scan tool Transmission OSS increase with the drive wheel speed?
--
Go to Testing for Intermittent Conditions and Poor Connections
Go to Step 3
3

1. <LI type=1>Turn OFF the ignition. <LI type=1>Disconnect the PCM.
2. Using the DMM and the J 35616 GM Terminal Test Kit, measure the resistance between the VSS high signal and VSS low signal circuits at the PCM connector.

Does the resistance measure within the specified range?
976-2354 Ω
Go to Step 4
Go to Step 7
4

1. <LI type=1>Place the transmission in NEUTRAL. <LI type=1>Select AC volts. <LI type=1>Prevent one rear wheel from turning.
2. Rotate the other rear wheel by hand, ensuring that the driveshaft is turning.

Does the voltage measure greater than the specified value?
0.5 V
Go to Step 5
Go to Step 12
5
Measure the resistance from the high signal circuit of the VSS to ground.
Does the resistance measure greater than the specified value?
50 K Ω
Go to Step 6
Go to Step 9
6

1. <LI type=1>Connect the PCM. <LI type=1>Disconnect the engine wiring harness from the VSS. <LI type=1>Turn ON the ignition, with the engine OFF.
2. Test the high signal circuit of the VSS for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs.

Did you find and correct the condition?
--
Go to Step 15
Go to Step 14
7

1. <LI type=1>Disconnect the engine wiring harness from the VSS.
2. Measure the resistance of the VSS.

Does the resistance measure within the specified range?
976-2354 Ω
Go to Step 8
Go to Step 13
8
Was the resistance measured in Step 3 greater than the specified value?
2354 Ω
Go to Step 10
Go to Step 11
9
Test the high signal circuit of the VSS for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs.
Did you find and correct the condition?
--
Go to Step 15
--
10

1. <LI type=1>Test the high signal circuit of the VSS for an open.
2. Test the low signal circuit of the VSS for an open. Refer to Testing for Continuity and Wiring Repairs.

Did you find and correct the condition?
--
Go to Step 15
--
11
Test the high signal circuit and the low signal circuit of the VSS for a short together. Refer to Circuit Testing and Wiring Repairs.
Did you find and correct the condition?
--
Go to Step 15
--
12

1. <LI type=1>Remove the VSS. <LI type=1>Inspect the output shaft speed sensor rotor for damage or misalignment.
2. Inspect the case extension bushing for wear.

Did you find and correct the condition?
--
Go to Step 15
Go to Step 13
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 Control Module References for replacement, setup and programming.
Did you complete the replacement?
--
Go to Step 15
--
15
Perform the following procedure in order to verify the repair:

1. <LI type=1>Select DTC. <LI type=1>Select Clear Info. <LI type=1>Operate the vehicle, so that the transmission output speed is greater than 250 RPM for 2 seconds. <LI type=1>Select Specific DTC.
2. Enter DTC P0502.

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 - Vehicle
System OK