I looked up on alldata for my 2002, the picture looks like it is riveted to the frame, here below I cut and paste what it says.
The solid state radiator fan relay is controlled by the Powertrain Control Module
(PCM) by way of a Pulse Width Modulated (PWM) signal. The relay control circuit supplies a 12 volt signal to the PCM. The PCM then pulses the ground circuit to achieve fan on time. The relay provides a voltage to the fan motors which is proportional to the pulse width it receives from the PCM. The duty cycle ranges from 30% for low speed operation, then ramps-up to 100% for high speed operation. This fan control system provides infinitely variable fan speeds, allowing for improved fan noise, A/C performance, better engine cooling, and additional vehicle power.
To control operation of the relay, the PCM looks at inputs from:
- Engine coolant temperature
- A/C pressure transducer
- Ambient temperature from the body controller
- Vehicle speed
- Transmission oil temperature
The PCM uses these inputs to determine when the fan should operate and at what speed