After having my 2006 RL parked in a garage, it was returned to me with a ton of electronic glitches. (Not saying they did anything wrong, just asking for thoughts on a likely fix)

Problems with pictures and DTCs below:
- nearly dead instrument cluster. Gauges are dead except for backlight illumination briefly at startup and brief message in small screen to return key to position 0 when the door is open and engine running.
- turn signals are not activating exterior lights and no interior turn indicators working, although hazard lights work normally with interior lights and sound.
- no a/c clutch engagement although the rest of climate control functions seem operational.
- no working power mirrors, windows or sunroof, although power locks work.

The nav system works as normal except trip status is not displaying any measured data.
XM system link errors attached below
Engine starting and running well and transmission shifting alright, although it feels like the ECU has been reset to factory with harder shifts and faster acceleration. These problems are constant, not intermittent.

Which fuses / loose connections / modules can cause this? Did a quick battery disconnect/reconnect, connection and fuse check but not sure which fuse would be responsible for all these seemingly random problems. Please share your thoughts? Thank you

 

Grab a voltmeter and see if your alternator is putting out 13.4V or so and if it is, get your battery tested. It’s probably a bad battery.

 

Charging voltage is 13.4 v and stable. Had battery and alternator problems with the RL before with older batteries and replaced the alternator a year ago. Never had problems like this.

 

Bad battery can cause all kinds of cascading errors in these cars. I’d take it to Autozone and get them to test it. Sounds like the alternator is working fine at least. If it’s not the battery, I’d check the various grounds in the engine bay and cabin if you can find them. Make sure they’re not corroded and are making good connection.

 

Will get the battery tested. Ground checks may be very possible. Northeast salt has not been kind to my car. Any diagrams or summary of ground points you know of online?

 

How long was it parked in the garage ? Long enough for the battery to go flat ?

 

Only if left in ACC, but started up fine. Battery tested good. Found that driver side fuse number 21 blew. Any thoughts on common shorts that cause fuse 21 to blow?

 

The 40A blower motor fuse? Seems unrelated, but I don’t know what could have popped that one. The blower could be bad and have an internal short. If it pops again, I’d start there.

EDIT: sorry I was looking at the under hood relay/fuse box. 21 on the driver side looks like it could be the cause. Did it fix the issues?