P0501
Refer to PCM, VSS Buffer, VSS, EBCMDiagnostic Chart (Part 1 Of 2):
Diagnostic Chart (Part 2 Of 2):
CIRCUIT DESCRIPTION
The speed sensor circuit consists of a magnetic induction type sensor, a vehicle speed sensor buffer module and wiring. Gear teeth pressed on the output shaft induce an alternating current in the sensor. This signal is transmitted to the buffer. The buffer compensates for various axle ratios and converts the signal into a square wave for use by the speedometer, cruise control, antilock brake and PCM. The buffer sends two different signals to the PCM.
CONDITIONS FOR SETTING THE DTC
^ The PCM performs this DTC diagnostic continuously.
^ The vehicle speed greater than 20 mph.
^ The four wheel low not selected.
^ The VSS buffer calculated speed is less than half the transmission calculated speed.
^ All of the diagnostic set conditions met for 2 seconds.
or
^ The PCM performs this DTC diagnostic continuously.
^ The VSS buffer calculated speed is greater than transmission calculated speed by 20 mph.
^ All of the diagnostic set conditions met for 2 seconds.
ACTION TAKEN WHEN THE DTC SETS
^ The PCM disallows all cruise control inputs.
^ The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM records the operating conditions at the time the diagnostic fails. This information stores in the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
^ A History DTC will clear when forty consecutive warm-up cycles during which the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from the start up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle.
^ Use of a Scan tool.
DIAGNOSTIC AIDS
Check connections at VSS buffer and PCM. Refer to 4L80-E Diagnostic Trouble Codes in Transmission if DTC P0722 or DTC P0723 is also set. Transmission and Drivetrain
TEST DESCRIPTION
The numbers below refer to the step numbers on the Diagnostic Table.
3. This tests for B+ at VSS buffer.
4. This tests for proper ground path for vehicle speed sensor signal buffer.