CLOCKSPRING
DESCRIPTION
The clockspring for this vehicle is internal to and serviced as a unit with the Steering Control Module (SCM) (4). The SCM is secured near the top of the steering column below the steering wheel. On vehicles so equipped, the SCM also includes an integral, internal Steering Angle Sensor (SAS) that is serviced as a unit with the SCM. The SCM is a modular unit that also interfaces with and supports the left (lighting) multi-function switch (1), the right (wiper) multi-function switch (2), the hazard switch (3), and the turn signal cancel cam. Each of these switches and the turn signal cancel cam can be separated from and are serviced individually from the SCM.
Besides the clockspring and SAS, the SCM contains an electronic circuit board and a microprocessor, which allows it to communicate with other electronic modules in the vehicle over the Controller Area Network (CAN) data bus. The SCM circuitry, the clockspring, and the SAS are all contained within a flat, round molded plastic case.
The SCM case includes two connector receptacles that face toward the instrument panel. Within the plastic case is a spool-like molded plastic rotor with a large exposed hub. The upper surface of the rotor hub has a large, keyed center hole, an index hole, two short pigtail wires with connectors, and two connector receptacles that face toward the steering wheel. Wound around the rotor spool within the case is a long ribbon-like tape that consists of several thin copper wire leads sandwiched between two thin plastic membranes. The outer end of the tape terminates at the connector receptacles that face the instrument panel, while the inner end of the tape terminates at the pigtail wires and connector receptacles on the hub of the clockspring rotor that face the steering wheel. The lower surface of the rotor hub has a molded plastic turn signal cancel cam with two lobes that is keyed to the clockspring rotor.
The service replacement SCM body is shipped with the clockspring pre-centered and with a molded plastic locking pin (5) installed. The locking pin secures the centered clockspring rotor to the SCM case during shipment and handling, but must be removed after the SCM is installed on the steering column and before the steering wheel is installed. (Refer to 8 - ELECTRICAL/RESTRAINTS/CLOCKSPRING - STANDARD PROCEDURE - CLOCKSPRING CENTERING).
The clockspring cannot be repaired. If the clockspring is ineffective, damaged, or if the driver airbag has been deployed, the SCM/clockspring/SAS unit must be replaced. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/STEERING CONTROL MODULE - REMOVAL).
OPERATION
The clockspring is a mechanical electrical circuit component that is used to provide continuous electrical continuity between the fixed instrument panel wire harness and certain electrical components mounted on or in the rotating steering wheel. On this vehicle the rotating electrical components include the driver airbag, the horn switch, the speed control switches, and the remote radio switches, if the vehicle is so equipped. The Steering Control Module (SCM)/clockspring is positioned and secured near the top of the steering column. The fixed connector receptacles on the back of the fixed SCM/clockspring case connect the clockspring to the vehicle electrical system through two take outs with connectors from the instrument panel wire harness.
The turn signal cancel cam is keyed so as to move with the rotation of the steering column shaft and the steering wheel. The cancel cam is secured and also keyed to the lower surface of the clockspring rotor hub, which indexes the clockspring rotor to the steering column shaft. Two short, yellow-sleeved pigtail wires on the upper surface of the clockspring rotor connect the clockspring to the driver airbag, while a steering wheel wire harness and a driver airbag jumper harness connected to the two connector receptacles on the upper surface of the clockspring rotor complete circuits to the horn switch, the two speed control switches and, if the vehicle is so equipped, to the optional remote radio switches on the steering wheel.
Like the clockspring in a timepiece, the clockspring tape has travel limits and can be damaged by being wound too tightly during full stop-to-stop steering wheel rotation. To prevent this from occurring, the clockspring is centered when it is installed on the steering column. Centering the clockspring indexes the clockspring tape to the movable steering components so that the tape can operate within its designed travel limits. However, if the clockspring is removed from the steering column or if the steering shaft is disconnected from the steering gear, the clockspring spool can change position relative to the other steering components. The clockspring must be re-centered following completion of this service or the tape may be damaged.
Service replacement SCM/clocksprings are shipped pre-centered and with a plastic locking pin installed. This locking pin should not be removed until the SCM/clockspring has been installed on the steering column. If the locking pin is removed before the SCM/clockspring is installed on a steering column, the clockspring centering procedure must be performed. (Refer to 8 - ELECTRICAL/RESTRAINTS/CLOCKSPRING - STANDARD PROCEDURE - CLOCKSPRING CENTERING).
The hard wired clockspring circuits as well as the hard wired inputs and outputs of the SCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the SCM or the electronic controls or communication between other modules and devices that provide features of the supplemental restraint system. The most reliable, efficient, and accurate means to diagnose the SCM or the electronic controls and communication related to SCM operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.