B124

The vehicle speed sensor uses a permanent magnet P.M. generator to produce an electrical signal representative of vehicle speed. This signal is sent to the ECM by CKTs 400 (VSS HI) & 401 (VSS LO) where the ECM buffers and amplifies the signal for its prospective uses. Output of the generator can be seen by using a digital voltmeter on the AC scale while rotating the generator drive (rotate front wheels).

Code B124 will set if the following conditions are present for 30 seconds:
^ Ignition "ON."
^ No code EO56 or EO57 set.
^ No code B334 or EO47.
^ Transaxle in 4th gear (EI82 "HI").
^ Engine RPM greater than 1300.
^ No vehicle speed input to the BCM from the ECM.

During the time the failure is present the continuous compressor at idle will be disabled.
1. If code EO24 is also set, then there is a vehicle speed sensor or ECM problem. These are diagnosed under EO24 diagnostic chart in ECM Diagnostic Charts. Testing and Inspection
2. This step checks for a speed signal at the BCM.
3. This step isolates the loss of a valid speed signal to the BCM by checking for a circuit problem in 817 or a faulty ECM.

Note on Intermittents
If an intermittent code B124 has been set, manipulate circuit 817 while observing BCM data parameter BD60. If a failure is induced, the reading will jump from a normal value to zero.