Courtesy and dome light stay on with door shut

If the dome lights in your 2009 Cadillac CTS are not turning off, it can be a frustrating issue. Here are some steps to diagnose and potentially fix the problem:
1. **Manually Turn Off the Dome Lights:**
- In most vehicles, including the Cadillac CTS, there's typically a manual switch on or near the dome light itself. Ensure this switch is in the "Off" position.
2. **Check for Open Doors:**
- Make sure all doors, including the trunk and the hood, are completely closed. Sometimes, a door ajar can prevent the dome lights from turning off.
3. **Interior Light Dimmer Control:**
- Check the position of the interior light dimmer control, which is usually located on the headlight switch or dashboard. If it's turned all the way up, it may keep the dome lights on. Adjust it to the lowest setting.
4. **Ignition Switch:**
- Ensure the ignition switch is in the "Off" position. Sometimes, if the ignition switch is left in the "Accessory" position, the dome lights may stay on.
5. **Faulty Door Switches:**
- Each door usually has a door switch that signals the lights to turn on when a door is opened and off when it's closed. One of these switches may be malfunctioning. You can try manually pressing and releasing each door switch to see if the lights respond.
6. **Battery Disconnect and Reconnect:**
- If the above steps don't work, you can disconnect the vehicle's battery for a few minutes and then reconnect it. This can sometimes reset the electrical system and resolve the issue.
7. **Consult the Owner's Manual:**
- Refer to your Cadillac CTS owner's manual for specific information about the dome light controls and troubleshooting tips.
8. **Professional Diagnosis:**
- If the issue persists, it may be related to a more complex electrical problem. In this case, it's advisable to consult a professional mechanic or an auto-electrician to diagnose and repair the problem.
It's important to be patient and methodical when troubleshooting this issue, as it can have various causes. If you're not comfortable working on the electrical system of your vehicle, seeking professional help is a wise choice to avoid further complications.

the courtesy and dome lights are operated by switches in the door frame look around the opening and look for a small black button
that button presses back in and breaks the circuit thereby putting out the light
if it is earthed ( grounded) at the back then the lights will stay on
there is one for each door and any one will keep the lights on

Your door switch is made into the door latch, you might try spraying WD-40 into the drivers door latch and work the latch open and closed. You will probably end up having a new latch installed though.

Glad you solved it.

There is no fuse marked for dome light's in the rear fuse box. The BCM - body control module controls the dome / courtesy light's .
The body control module (BCM) monitors the courtesy lamp switch signal circuit in order to determine when the courtesy/dome lamps should be illuminated. When the BCM senses that the courtesy lamp switch signal circuit is grounded when the switch is activated, the BCM will directly illuminate the courtesy/dome lamps.
DTC B3801 Passenger Compartment Lamp Request Circuit

You should possibly think about taking your vehicle to a qualified repair shop !
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the courtesy lamp switch parameter in the body control module (BCM) data list.
Does the scan tool display INACTIVE?
YES - Go to Step 3
NO - Go to Step 4
3
Activate the courtesy lamp switch.
With the scan tool, observe the courtesy lamp switch data parameter.
Does the courtesy lamp switch data parameter change state?

• Test the courtesy lamp switch for sticking in the ON position.
• Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

One of your door sensors (or trunk sensor) is signaling that it is open or the dimmer switch is turned all the way up, which turns on the dome and foot lamps. Try turning the dimmer switch all the way down. If this does not fix the problem you will have to get all the door sensors (and trunk sensor) tested to determine which one needs to be replaced.

To temporarily solve the light problem, I taped a washer to the inside of the door where the door hits the plunger on the light switch. A permanent solution would be to drill a hole in the door at this spot and put a self taping screw in that will trigger the switch sooner. I figured out the reason the dome light stayed on is due to the courtesy light timer and the lights would have eventually gone off.

Don't think you have a door ajar switch problem , more then like the lighting control module is the culprit . Does the door ajar light on the instrument cluster stay lit ?
The interior lighting can be separated into two distinct modes of operation: the courtesy lighting and the demand lighting. The lighting control module (LCM) controls all of the interior lighting in the vehicle, as described in the following text.
The front dome lamps, rear reading lamps, and instrument panel courtesy lamps, can be illuminated either by opening any of the vehicle doors (courtesy lamp function) or by depressing the headlamp switch (demand lamp function).
When any door is open, the door ajar switch grounds an input to the LCM which then sends power to the courtesy lamps. The voltage sent to the courtesy lamps gradually increases from 0 volts to 12 volts within 500 ms (± 50 ms), to achieve the theater lighting effect. When the door(s) are closed the door ajar switch(es) break(s) the ground to the LCM input which then gradually reduces the power from 12 volts to 0 volts within 5 seconds. (± .5 second).
When the headlamp switch is depressed it grounds an input to the LCM which in turn sends 12 volts to the front dome lamps, rear reading lamps, and instrument panel courtesy lamps. When the headlamp switch is depressed a second time, it breaks the ground to the LCM input which then ceases to send power to the front dome lamps, rear reading lamps, and instrument panel courtesy lamps.

The battery saver will disrupt power to the courtesy lamps after 10 minutes, the demand lamps after 30 minutes, and the headlamps after 10 minutes. Turning the ignition switch to the RUN or ACC position will terminate the battery saver feature by disabling the interrupt timers and reinstate power to the lamps.
Do you know what DTC'S are ? diagnostic trouble codes !
LCM Diagnostic Trouble Code (DTC) Index DTC Description Source Action B1322 Driver Door Ajar Circuit Short to Ground LCM Go To Pinpoint Test F . B1442 Door Handle Switch Circuit Failure LCM Go To Pinpoint Test G . B1445 Door Handle Switch Circuit Short to Ground LCM Go To Pinpoint Test G . B1563 Door Ajar Circuit Failure LCM Go To Pinpoint Test C . B1566 Door Ajar Circuit Short to Ground LCM Go To Pinpoint Test H . B1685 Lamp Dome Input Circuit Failure LCM Go To Pinpoint Test I . B1687 Lamp Dome Input Circuit Short to Battery LCM Go To Pinpoint Test I . - All Other DTCs LCM REFER to Section 419-10 .

PINPOINT TEST C: THE COURTESY LAMPS STAY ON CONTINUOUSLY CONDITIONS DETAILS/RESULTS/ACTIONS C1 CHECK THE SYSTEM OPERATION Open and close each door, making sure that each door is completely closed.

• Are the courtesy lamps still illuminated after the 25 second time-out period?

Yes GO to C2 .

No The system is operating correctly. C2 TEST DOME LAMP SWITCH Depress the dome lamp switch.

• Are the courtesy lamps still illuminated?

Yes DEPRESS the dome lamp switch a second time. GO to C3 .

No The system is operating correctly. C3 CHECK THE LIGHTING CONTROL MODULE
LCM C2145a

• Are the courtesy lamps still illuminated?

Yes REPAIR circuit 53 (BK/LB). REPEAT the self-test. CLEAR the DTCs.

No INSTALL a new LCM. REFER to Section 419-10 . REPEAT the self-test. CLEAR the DTCs.

Are you sure that the thumb wheel switch beside the headlamp switch is not turned all the way up until it clicks?
If it is staying on for 10 minutes this means that the smart junction box is seeing a demand for the interior lights from something like a door ajar switch or the thumb wheel. If it sees that the igntion is in the off position it will turn the lights off after 10 minutes to conserve battery power.
Normal operation is:
The interior lighting delay feature provides temporary illumination of the courtesy lamps after the doors are opened and then closed. The interior lighting delay feature keeps the courtesy lamps on for a period of 25 seconds after all the doors are closed. If during the 25-second delay time the SJB detects that the ignition has been switched out of off, or if the vehicle is locked using the RKE, the courtesy lamp illumination is discontinued

The door ajar/courtesy light switch that is mounted to the door latch inside the door is sticking, this is a very common issue with all late model Fords from 90's up.