Note On Intermittents

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

NOTE: The following numbered steps refer to circled numbers on diagnostic chart. See Fig 1 . For circuit identification, see Fig 2 .

If DTC EO24 is also set, then there is a vehicle speed sensor or ECM problem. See SELF-DIAGNOSTICS -- ALLANTE article in ENGINE PERFORMANCE.
This step checks for a speed signal at the BCM.
This step isolates the loss of a valid speed signal to the BCM by checking for a problem in CKT 817 or a faulty ECM.

Fig 1: DTC B124: Vehicle Speed Sensor Circuit Problem Flow Chart

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC B124: Vehicle Speed Sensor Circuit Problem Flow Chart Circuit

Courtesy of GENERAL MOTORS CORP.