Just replaced the battery. Did a 20 mi test drive. Now the Aspirator Fan (“Cabin Humidity and Temp Sensor”) is always on. Pulled codes. Got ECU1 ($FD00) and ECU2 ($FD20). Checked on line. Many different answers but seems to be an ECM/module communication issue. Doesn’t look like the Climate Control Module is the problem since AC/Heat/Blower all work fine. Checked on line. Recommend was disconnect the battery for 20 min and maybe the CCM will reset. Didn’t work. Took off the dash panel to get access to the fan. Used electronics grade compressed air to clean. Nothing. If I understand correctly, the fan has both a relay and temp sensor. Is replacing the fan a good possible solution? No wiring or ground problems. Suggestions appreciated! Thanks.

 

I'd look first at relay R3 in the CJB. It a delayed power off relay that feeds power to the fan, which you note is always on. Could be the relay is faulty.

 

Thanks for your help. Cheaper and easier than fan remove/replace. Finding a replacement relay probably a challenge.

 

How have you determined that the aspirator fan is “always” on? In proper operation the fan starts instantly when the outside door handle is pulled and it remains active until about 20 minutes after engine shut down. This is on purpose to permit rapid climate control when the car is in regular use. Unless you have left the driver’s window down and poked your head inside a half hour after engine shut-down, you might well assume that the fan never shuts down!

 

@CA Jag , if you are trying to reset a module, you might try performing a hard reset instead of simply disconnecting the battery. It's possible you did not fully discharge the capacitors. The following is from Jaguar's “Technical Training 688-JAG: Advanced Electrical Systems and Diagnostics”, page 3-15, covering Control Module Programming:

 

they always run when you’re supposed to be in the car. if you can’t stand it get a new one it’ll be quiet

 

He has a vert so it was easy to assume it was literally always on and could be heard, but point taken.

 

Exactly what I thought. Fan ran and never shut off while I worked on the car. Seemed to be running at night when the car was asleep. Now understand that it turned on when I opened the door. The fan is super quiet. LOL I've actually never heard it until partial remove from the dash. Left the door side window down and put the car to sleep. Checked later. Fan was off. Easily to tell if it was running by holding it.

Overnight battery drop from 12.9>12.6 was a concern. Thought maybe fan related. Maybe VOM related. The whole parasitic draw measure w/ a 40A clamp meter another story. Even after zero reset, numbers seem to bounce. Clamp placement and alignment factor in. Batteries are good. PD seems to be in the 10-50 mA range.

 

Thanks for the suggest.

 

Again thanks to everyone for feedback and suggests.