The multi-function switch is the switch you turn on the wipers with.
The vehicle operator initiates all wiper and washer system functions with the control knob on the end of the control stalk of the multi-function switch that extends from the left side of the steering column, just below the steering wheel. Rotating the control knob on the end of the control stalk, selects the Off, Delay, Low, or High wiper system operating modes. In the Delay mode, the control knob also allows the vehicle operator to select from one of five intermittent wipe Delay intervals. Depressing the control knob towards the steering column actuates the momentary washer system switch, which selects the Wash, Wipe-After-Wash, and Pulse Wipe Modes depending upon when and how long the switch is held closed. The multi-function switch provides hard wired resistor multiplexed inputs to the instrument cluster for all of the wiper and washer system functions. The instrument cluster then sends electronic messages to the Front Control Module (FCM) over the Programmable Communications Interface (PCI) data bus requesting the appropriate wiper and washer system operating modes.
Wiper and washer system operation are completely controlled by the instrument cluster and FCM logic circuits, and that logic will only allow these systems to operate when the ignition switch is in the Accessory or On positions. Battery current is directed from a B(+) fuse in the Integrated Power Module (IPM) to the wiper on/off relay and the wiper high/low relay in the IPM through a fused B(+) circuit. The FCM uses low side drivers to control wiper system operation by energizing or de-energizing the wiper high/low and wiper on/off relays. The FCM uses a high side driver to control the operation of the washer pump motor unit. The multi-function switch circuitry receives a clean ground output from the instrument cluster on a multi-function switch return circuit, then provides resistor multiplexed inputs to the instrument cluster on an intermittent wipe mux circuit to indicate the selected wiper system mode and on a wash/beam select mux circuit to indicate the selected washer system mode.
The hard wired circuits and components of the wiper and washer system may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic methods may not prove conclusive in the diagnosis of the instrument cluster, the FCM, or the electronic message inputs to or outputs from the instrument cluster or FCM that control the wiper and washer system operating modes. The most reliable, efficient, and accurate means to diagnose the instrument cluster or the FCM inputs and outputs related to the various wiper and washer system operating modes requires the use of a DRBIII® scan tool. Refer to the appropriate diagnostic information.
Do you know what codes are in the FCM?