Test Procedure

WARNING: This page is about a different car, the 1989 Cadillac Allante. However, it is still accessible from the selected car via links, so may be relevant.

If code E024 is also set, then there is a vehicle speed sensor or ECM problem. These are diagnosed under E024 diagnostic chart. See 1989 SELF-DIAGNOSTICS -- ALLANTE article in ENGINE PERFORMANCE.
Checks for speed signal at BCM.
Isolates the loss of a valid speed signal to the BCM by checking for a circuit problem in circuit No. 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.