Jensen RV cab radio does not have power in the key accessory mode.

My first guess would be a faulty ignition switch. There could also be a short in the wiring - there has to be power going to the fuel pump relay and the ignition to keep it running. You should be able to turn the key on and off and check those circuits with a meter or test light.

This is the radio diagram for fuse 17

hmm... well normally that line will also power the clock but i cant see it drawing that much power :/ If you take that fuse out does it still flatten your battery? what about immobilizer? or car alarm? but whatever it is... you may have to divert power to ignition instead of accessories so that it only uses power when the key has been turned to 'on' position... but there's definitely something using power there.... I'm curious!

Hi, your factory Sunfire wire colors are pasted below. The yellow wire should be accessory. This should connect to the stereo's red power wire. The orange "always hot" wire should connect to the stereo yellow wire--this is only used to keep your station presets in memory. Please let me know if you have more questions, and thanks for using FixYa.

2004 Pontiac Sunfire Car Stereo Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Gray
Car Stereo Dimmer Wire: Brown
Car Stereo Antenna Trigger Wire: Pink
Car Stereo Amp Trigger Wire: Pink
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

sounds like its wired wrong .. there are three power inputs to the radio .. one is on all the time .. its for the clock only ... the second is from the panel lamp dimming circuit .. it turns on when the panel lights are on ... the third is the main power to the radio .. it is only on when the ignition is on or in accessory mode ..

Check fuses first to see that you have noon of them blown.

Yes i can solve your problem first you must have the proper radio code 4 numbers and shut off engine and leave radio on with key on accessory with it displaying off leave it the radio on for 3 hours then enter the proper code and it should work fine THIS IS THE FACTORY PROCEDURE

1999 GMC Sierra Truck Radio Wiring Guide
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black/White
Car Radio Illumination Wire: Brown
Car Stereo Dimmer Wire: Gray
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue
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check the radio fuse also check power accessory fuse... hope i could help

You have all the necessary power wires attached where required?