Powertrain Controls - ECM/PCM

DTC 24 Vehicle Speed Sensor (VSS) Circuit Low (Trans Output Speed Signal):

Vehicle Speed Sensor (VSS) Circuit:

CIRCUIT DESCRIPTION
The speed sensor circuit consists of a magnetic induction type sensor, a Vehicle Speed Sensor (VSS) buffer module and wiring. Gear teeth pressed onto the output shaft induces an alternating voltage into the sensor. This signal is transmitted to the VSS buffer module. The VSS buffer module compensates for various final drive ratios. The VSS buffer module will also convert the AC VSS signal into a 40 Pulse Per Revolution (PPR) DC signal on CKT 437 to indicate transmission output speed.

DTC 24 WILL SET WHEN
^ Not in P/N.
^ CKT 437 voltage is constant.
^ Engine speed is greater than 3000 RPM.
^ Output speed is less than 200 RPM.
^ Manifold Absolute Pressure (MAP) is greater than 40 kPa.
^ Throttle Position (TP) is between 10% and 100%.
^ All conditions met for 3 seconds.
^ No DTC(s) 21, 22, 28, 33, or 34.

ACTION TAKEN (TCM will default to)
Second gear only at maximum line pressure.

DTC 24 WILL CLEAR WHEN
The ignition is cycled "OFF" then "ON."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test checks for voltage to the VSS buffer module.
2. This test checks the ground circuit to the VSS buffer module.
3. This test checks the Vehicle Speed Sensor (VSS) circuit at the VSS buffer module.
4. This test checks for an output speed signal from the VSS buffer module.

DIAGNOSTIC AIDS
^ DTC 24 will set when no vehicle speed is detected at start off.
^ DTC 72 will set when vehicle speed has been detected and is lost.