Anyone know if there is a corelation between the trans fluid temp or level and the engine cooling fan engaging?

Fan is coming on at less than 200 degree ECT and I simultaneously see the engine temp gauge in the dash drop to zero and feel a drop in power. Happens when pulling a hill and lugging the motor.

Hooked up a SCT and watched the display as I drove. Coolant and oil temps don't go above 200 degrees. The transmission temp reads in the normal rnge on the dash but shows invalid on the SCT display.

Checked trans fluid level and it was down 3 quarts. Don't know why as I've seen no leaks but it was low.

So I'm wondering if the transmission temps or fluid level (or anything else for that matter can trigger the cooling fan besides actual coolant temperature.

 

Yes there are several sensors the PCM uses to determine when it ramps up the fan.....coolant temp, trans temp, egr temp, and I think 1-2 more.

 

could be loosing fluid into the tail shaft housing. It would hold about that amount and I've seen this exact thing before.

 

So it is possible that my trans temp sensor is triggering the fan then. Possibly a bad sensor or harness issue? Any idea why the trans temp gauge in the dash appears to read normal but the display on my SCT tuner reads TFT invalid? I assume they would both be reading from the same sensor right?

Also, any thoughts on why the coolant temp gauge in the dash drops to zero when the fan kicks on?

 

When you say you have seen this exact thing before are you just refering to the mysterious fluid loss or the other issues I'm having as well?

 

Fan Speed Sensor (FSS)The FSS is a Hall effect sensor integral to the visctronic drive fan (VDF). The PCM monitors the sensor input and controls the VDF speed based upon the engine coolant temperature, the transmission fluid temperature, and the intake air temperature (IAT) requirements. When an increase in fan speed for vehicle cooling is requested, the PCM monitors the FSS signal and outputs the required PWM signal to a fluid port valve within the VDF.

Visctronic Drive Fan (VDF)The VDF is an electrically actuated viscous clutch that consists of 3 main elements:
• a working chamber
•a reservoir chamber
•an actuator (electromechanical valve and speed sensor)

The actuator valve controls the fluid flow from the reservoir into the working chamber. Once viscous fluid is in the working chamber, shearing of the fluid results in fan rotation. The valve is activated via a pulse width module (PWM) output signal from the PCM. By opening and closing the fluid port valve, the PCM controls the fan speed. Fan speed is measured through a Hall effect sensor, and is monitored by the PCM during closed loop operation. The PCM optimizes the fan speed based on the engine coolant temperature, the engine oil temperature, the transmission fluid temperature, the intake air temperature, or air conditioning requirements. When an increased demand for fan speed is requested for vehicle cooling, the PCM monitors the fan speed through the Hall effect sensor. If a fan speed increase is required, the PCM outputs the PWM signal to the fluid port, providing the required fan speed increase. During the key on, engine running (KOER)self-test, the PCM commands a 100% duty cycle. A diagnostic trouble code (DTC) is set if the PCM detects the voltage on the valve control circuit is not within the expected range or if the fan speed is less than a calibrated value.

 

While pulling the hills is the A/C on MAX?

Josh