DTC 16

Vehicle Speed Signal Fault:

Vehicle Speed Signal Buffer Fault:

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 Powertrain Control Module (PCM). The buffer sends two different signals to the PCM. The 437 circuit relays the transmission output speed which is used to control shift points, line pressure, Torque Converter Clutch (TCC), Diagnostic Trouble Code (DTC) 24 and DTC 72. The 817 circuit relays the vehicle speed which is used to control engine operating functions and DTC 16. When DTC 24 or 72 is set, second gear only at maximum line pressure will occur.

DTC 16 WILL SET WHEN
^ Greater than 20 mph.
^ 1000 to 4400 RPM.
^ CKT 817 open or grounded.
^ All conditions must be met for 2 seconds.

ACTION TAKEN (PCM will default to)
No cruise control or fuel cutoff.

DTC 16 WILL CLEAR WHEN
The fault condition(s) no longer exist, and the ignition switch is cycled "OFF" then "ON."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This tests for B+ at Vehicle Speed Sensor (VSS) buffer.
2. This tests for proper ground path for vehicle speed sensor signal buffer.
3. This tests for vehicle speed sensor signal buffer signal to PCM.
4. This tests for a signal from VSS buffer to the PCM.

DIAGNOSTIC AIDS
Check connections at VSS buffer and PCM. Refer to Diagnostic Trouble Codes, if DTC 24 or DTC 72 is also set. Testing and Inspection