Dome light and reading lamps stay on and will not cut off.

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.

Which of these lamps do not work , ones that can be dimmed or ones that can't ?
Interior Lamps
The interior lamps consists of two groups, lamps that can not be dimmed and lamps that can be dimmed. This first group consists of lamps that may not be dimmed. This Includes those lamps that may be manually turned on by placing the interior lamp switch to the DOME position, or by opening a door or a compartment:
• Auxiliary dome lamp (SEO, RPO 6C7)
• Dome lamp
• Inside rear view mirror lamps
• Instrument panel (I/P) courtesy lamps
• Reading lamps
• Rear compartment courtesy lamp
• Sunshade vanity mirror lamps
Battery positive voltage is applied at all times to the driver information center (DIC)/remote keyless entry (RKE) fuse and to the switched side of the BATT RUNDOWN PROTECTION relay in the right I/P junction block. The DIC/RKE fuse supplies battery positive voltage to the coil side of the BATT RUNDOWN PROTECTION relay. When the ignition is turned to the ON position, the body control module (BCM) provides a ground to the courtesy lamp relay control circuit. This energizes the BATT RUNDOWN PROTECTION relay and applies battery positive voltage to I/P BRP fuse and to the TRK/ROOF/BRP fuse. Battery positive voltage is applied from the I/P BRP fuse to the I/P courtesy lamps and to the courtesy lamp supply voltage circuit to the BCM. Battery positive voltage is also applied from the TRK/ROOF/BRP fuse to the:
• Rear compartment courtesy lamp
• Dome lamp
• Inside rear view mirror lamps
• Roof rail/reading lamps assembly
• Sunshade vanity mirror lamps
If the BCM receives a door lock or unlock input signal, the BCM will activate the BATT RUNDOWN PROTECTION relay, which provides battery positive voltage to all interior courtesy lamps. When any door is opened, the door jam switch contacts close and the BCM receives a door-open input signal. The BCM then applies a ground to the interior lamp control circuit and to the courtesy lamp low control circuit illuminating the courtesy and dome lamps.
After all the doors are closed, the courtesy lamps remain illuminated for approximately 40 seconds. The courtesy lamps will also turn on and remain illuminated for approximately 15 seconds after the ignition key is removed, prior to any door being opened.
When the headlamp switch is placed in the DOME position, the BCM receives a ground signal. The BCM then applies a ground to the interior lamps control circuit. This illuminates the dome and roof rail lamps.
The courtesy lamps will normally turn off using the theater dimming feature. The BCM provides a pulse width modulated ground to all courtesy/reading, dome, and inside rear view mirror lamps for the theater dimming feature. The BCM will immediately turn off the courtesy lamps if a door lock command is received with all the doors closed, or if the ignition switch is turned to either the ON or RUN position.
The BCM activates the interior lighting output 15 seconds after receiving the class 2 message "Airbags Deployed" from the SDM. The interior lamps remain activated for 25 minutes.

Hooking up a factory or someother type of professional scan tool an checking for codes in the BCM - body control module could shed some light on the problem .
DTC B2655 Courtesy Lamp Low Control Circuit High
DTC B2654 Courtesy Lamp Low Control Circuit Low
The body control module (BCM) controls the courtesy lamps through the courtesy lamp low control circuit. The BCM grounds the courtesy lamp low control circuit which completes the interior lamps circuit, and the lamps illuminate.
DTC B2618 Courtesy Lamps Supply Voltage Circuit High
The body control module (BCM) controls the instrument panel (I/P) courtesy lamps through the courtesy lamps supply voltage circuit. The BCM grounds the courtesy lamps low control circuit which completes the I/P courtesy lamps ground circuit, and the lights illuminate.
DTC B2617 Courtesy Lamps Supply Voltage Circuit Low

The BCM supplies a ground to turn the lights on . One of the grounds for the BCM could faulty - lose , corroided etc. Looking at factory service info I see two ground points for the BCM - G201 & G203
G201
Under the I/P, to the right of the steering column, on the I/P support bracket

G203
Under the I/P, to the right of the steering column, on the I/P support bracket

could be a problem with the BCM

Interior lights and the power door locks are controlled by a electronic control module . Hooking up a factory or some other type professional scan tool an checking for codes an viewing input data to these control modules would be the first thing to do.
The interior lighting system consists of the following:

• lighting control module (LCM)
• driver door module (DDM)
• instrument panel
• dome/map combination
• courtesy/reading lamps
• orientation light
• door lamps
• footwell lamps
• luggage compartment lamp
• glove compartment lamp
• vanity mirrors
• door ajar switches
• viewing wiring diagrams an checking power and ground circuits for these modules would be the next step if no codes were found . Principles of Operation
  Lighting Control Module This vehicle uses a lighting control module (LCM). The LCM is a microprocessor-based module that controls several vehicle subsystems, responds to electrical input signals from various switches, sensors, and external modules and is located on the LH side of the instrument panel. LCM subsystem functions include:
  
  • headlamps with autolamps
  • turn signal lamps/hazard flasher lamps
  • cornering lamps
  • parking lamps
  • daytime running lamps
  • interior lamps
  • demand lamps
  • battery saver
  The LCM interfaces with the driver door module (DDM) via the standard corporate protocol (SCP) network for the illuminated entry feature.
  The interior lamp is illuminated by pressing the individual interior lamp switch. The interior lamp is also illuminated by door ajar switches located in the door latches, when any door is opened. A theater lighting feature gradually increases or decreases the light intensity when switched by opening or closing a door.
  The dome/map lamp combination are located on each side of the interior lamp. The map lamps are operated independently of the interior lamp by two switches located on the interior lamps.
  The interior lamps are illuminated by holding the panel dim switch in the UP position until the dome lamps turn on. The interior lamp also illuminates when a door is opened and actuates the door ajar warning lamp switch in the door latch.
  The front map lamps are powered by the demand lighting circuit and the interior lighting circuit.
  The rear passenger reading lamps are incorporated into the rear seat assist handle and are located over the rear door openings. These lamps are illuminated through power supplied by the LCM demand lighting circuit.
  Interior lamps (controlled by the LCM) are activated by using the dome lamp switch (instant ON/OFF response) or when a door is ajar. The following lamps illuminate for interior lighting:
  
  • instrument panel interior lamps
  • front map lamps
  • rear reading lamps
  • door lamps
  Demand lighting includes lamps that are illuminated by the customer by directly actuating a switch. The front dome/map lamps are located in the overhead console. Each lamp is controlled by its own switch.
  The following demand lamps are powered by the demand lighting output of the LCM:
  
  • glove compartment lamp
  • vanity mirror lamp
  • luggage compartment lamp
  Each lamp has a dedicated switch that closes to ground to illuminate the lamp.
  The front map lamps are powered by either the demand lighting circuit or the interior lighting circuit, depending upon the position of the switch associated with each lamp. When the customer turns the front map lamp switch ON, the front map lamp is illuminated through power supplied by the LCM demand lighting circuit. If the customer moves the map lamp switch to the OFF position, the power from the LCM demand lighting circuit is interrupted and the lamp is reconnected to the interior lighting circuit.
  The rear reading lamps are powered by either the interior lighting circuit or the demand lighting circuit.
  The luggage compartment lamp is controlled by the trunk ajar switch, and is powered by the demand lighting output from the LCM, and is mounted near the center of the upper rear panel.
  The glove compartment lamp system consists of a glove compartment lamp switch and wire and miniature bulb assembly. Opening the glove compartment door closes the switch which provides power to the glove compartment lamp switch and wire. The glove compartment lamp switch is grounded to the body sheet metal.
  The vanity mirror lamp system consists of a switch and bulb assembly in the RH inside visor and the LH inside visor. Lifting the vanity mirror cover closes the vanity mirror lamp switch and provides power to the lamps.
  The illuminated entry system is controlled by the LCM and provides interior lighting upon entry to the vehicle.
  Interior lamps will be illuminated for 25 (±1) seconds which includes a theater lighting ramp-up time (0.5 seconds). This time interval does not include the theater lighting ramp-down time. Interior lamps will be turned off before the 25 (±1)-second timeout if the ignition switch is turned to the RUN or ACC position.
  The illuminated entry system has the following additions to accommodate the remote entry system: pressing the unlock button on the remote transmitter will activate the illuminated entry system (with theater ramp-up). When the driver door module detects a button press, it sends a signal on the J1850 communication network activating the interior lamps. The lighting control module will turn off the lamps by sensing the all doors lock signal.
  The battery saver feature prevents excessive drain from loads inadvertently left on. When the ignition switch is turned OFF, power is interrupted to the interior lamps and headlamps (after a 10-minute timeout) and the demand lamps (after a 30-minute timeout).
  The battery saver has the following inputs:
  
  • luggage compartment door ajar switch
  • dome lamp switch
  • ignition switch status
  • illuminated entry signal
  • headlamp switch
  • driver/passenger door ajar entry switch
  • keyless entry remote transmitter
  • door unlock, luggage compartment door release

should be on side of the roof light assembly.by rear view mirror area,you will see some toggle switches

If this is the factory sunroof try finding the motor crank in the glove box and removing the plug in the headliner between the rear view mirror and the sunroof. Insert the crank (it is an hex wrench) and crank the roof closed.
If you have the dome/map lights pry out the lens of the light and remove the screws behind the lens to remove the overhead console and in the sunglass holder.
The motor is at the front of the roof and you can crank at the center of the motor drive.

its either a bad door switch,or could be the dome override switch by headlight switch,or your interior light switch is all the way up

all the lights above the dash do not work ?????? DOME light's ??? No light's come on when you open the door or any door ? Wouldn't think all the door ajar switches bad at one time .
Interior Lamps
The interior lamps consists of two groups, lamps that can not be dimmed and lamps that can be dimmed. This first group consists of lamps that may not be dimmed. This Includes those lamps that may be manually turned on by placing the interior lamp switch to the DOME position, or by opening a door or a compartment:
• Auxiliary dome lamp (SEO, RPO 6C7)
• Dome lamp
• instrument panel (I/P) compartment lamp
• Inside rear view mirror lamps
• I/P courtesy lamps
• Reading lamps
• Rear compartment courtesy lamp
• Sunshade vanity mirror lamps
Battery positive voltage is applied at all times to the DIC/RKE fuse and to the switched side of the BATT RUNDOWN PROTECTION relay in the right I/P junction block. The DIC/RKE fuse supplies battery positive voltage to the coil side of the BATT RUNDOWN PROTECTION relay. When the ignition is turned to the ON position, the body control module (BCM) provides a ground to the Inadvertent relay control circuit. This energizes the BATT RUNDOWN PROTECTION relay and applies battery positive voltage to I/P BRP fuse and to the TRK/ROOF/BRP fuse. Battery positive voltage is applied from the I/P BRP fuse to the I/P courtesy lamps, I/P compartment lamp and to the I/P compartment feed circuit to the BCM. Battery positive voltage is also applied from the TRK/ROOF/BRP fuse to the:

If the BCM receives a door lock or unlock input signal, the BCM will activate the BATT RUNDOWN PROTECTION relay, which provides battery positive voltage to all interior courtesy lamps. When any door is opened, the door jam switch contacts close and the BCM receives a door-open input signal. The BCM then applies a ground to the theater dimming ground control circuit illuminating the courtesy and dome lamps.
After all the doors are closed, the courtesy lamps remain illuminated for approximately 40 seconds. The courtesy lamps will also turn on and remain illuminated for approximately 15 seconds after the ignition key is removed, prior to any door being opened.
When the headlamp switch is placed in the DOME position, the BCM receives a ground signal. The BCM then applies a ground to the theater dimming ground control circuit. This illuminates the dome and roof rail lamps.
The courtesy lamps will normally turn off using the theater dimming feature. The BCM provides a pulse width modulated ground to all courtesy/reading, dome, and inside rear view mirror lamps for the theater dimming feature. The BCM will immediately turn off the courtesy lamps if a door lock command is received with all the doors closed, or if the ignition switch is turned to either the ON or RUN position.
The BCM activates the interior lighting output 15 seconds after receiving the class 2 message "Airbags Deployed" from the sensing and diagnostic module (SDM). The interior lamps remain activated for 25 minutes.

The door ajar switch is part of the lock actuator inside the door !

• There is a dome light switch on the dash. Turn it all the way to the right and it will click. Torn it to the left to turn the dome light off.

Regards, Tony

Interior Lights Circuit Description
By using a feature called inadvertent power control, the body control module (BCM) supplies power to all of the following components:
• The courtesy lamps
• The dome lamps
• The rear view mirror reading lamps
• The instrument panel compartment lamp
• The rear compartment lamp
The left front door ajar switch turns the interior lamps on through the BCM by grounding CKT 394. When the left front door is open, the switch is closed. This condition provides a ground and a door open input to the BCM. The BCM then grounds the following lamps through CKT 156 in order to turn the lamps on:
• The courtesy lamps
• The dome lamp
• The rearview mirror lamps
The right front door ajar switch and the rear door ajar switches turn the interior lamps on by grounding CKT 395 from the BCM.
When the ignition key is removed from the lock cylinder, the interior lamps remain on for approximately 40 seconds.
The BCM provides an interior lamps-on delay after a door is opened. The lamps remain on for approximately 40 seconds or until the ignition switch is turned to the ON position. The 40 second lamps-on delay reduces to 4 seconds if a door is opened within 2 minutes of the ignition switch being moved from the ON position. The interior lamps immediately turn off when the vehicle begins to move.
The dome lamp OFF-DOOR-ON switch controls the dome lamp. When the switch is in the OFF position, the dome lamp remains off. When the switch is in the DOOR position, the dome lamp lights when a door is opened by the BCM grounding CKT 156. When the switch is in the ON position, ground is supplied through CKT 750. The rear view mirror reading lamps are controlled by the rear view mirror reading lamps switch or through CKT 156 from the BCM.
Voltage is supplied at all times to the BCM through the INT LPS fuse. The BCM supplies voltage to the interior lamps through CKT 1732.

Battery Run Down Protection
When the ignition switch is in the OFF position, the BCM turns off the power to all of the interior lamps after 18-22 minutes.
The BCM will reset the inadvertent power control relay output when one of the following actions is performed:
• Open or close a door.
• Turn the ignition switch to the ON position.
• Turn off any interior lamps that may be on.
• Press the power door lock switch/keyfob button.
• Press the decklid release keyfob button.

Courtesy or Dome Lamps Always On
Step
Action
Yes
No
1
Did you perform the Lighting Systems Diagnostic System Check?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Lighting Systems
2
Use the Scan Tool in order to command the courtesy lamps OFF.
Do the courtesy lamps turn OFF?
YES - Go to Step 4
NO - Go to Step 3
3
Test for a short to ground in the courtesy lamps control circuit (156). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - System OK
NO - Go to Step 7
4
Test for a short to ground in each door jamb switch circuit:
• Circuit 394-Driver door
• Circuit 395-Passenger door(s).
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - System OK
NO - Go to Step 5
5
Test each door jamb switch for proper operation. Refer to the following:
• Open switch with the door closed
• Closed switch with the door open
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find a malfunctioning door jamb switch?
YES - Go to Step 6
NO - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
6
Replace the malfunctioning door jamb switch. Refer to Door Jamb Switch Replacement in Doors.
YES - Is the repair complete?
NO - System OK
--
7
Important: Perform the set up procedure for the body control module.
Refer to Body Control Module (BCM) Programming/RPO Configuration .
Replace the body control module. Refer to Body Control Module Replacement in Body Control System.
Did you complete the replacement?
System OK
Instal the door jamb switch wire harness.
Install the door jamb switch (2).

The interior lamps system consists of 2 main features. Illuminated entry and a battery saver feature that will turn the interior lights off after 20 minutes if they are left On with all doors closed and the ignition Off. The body control module (BCM) controls both of these functions. Battery power is supplied by the BCM through CKT 1732 to the following lamps:
• The dome lamp
• The map lamps
• The rear reading lamps
• The rear dome lamp
• The cargo lamp
• The glove compartment lamp
• The courtesy lamps
• The sunshade lamps
The BCM also controls the ground circuit side of the dome lamp and reading lamps for illuminated entry. The dome lamp and reading lamp will remain on for 20 seconds after the ignition key is removed and the last door is closed. In addition, if the vehicle is equipped with remote keyless entry (RKE), the dome and reading lamps will turn On and stay on for 20 seconds after an UNLOCK signal is received from the keyless entry transmitter.
The reading lamps, dome lamp and map lamps can be turned On at any time by moving the appropriate switch to the On position.
The rear dome lamp is fed battery voltage through CKT 1732 from the BCM, through the liftgate ajar switch, and is grounded through CKT 650 to the rear ground splice pack. The rear dome lamp will turn on when the liftgate is opened. The cargo lamp is fed battery voltage through CKT 1732 from the BCM, through CKT 744 and grounded through the decklid ajar switch.
The courtesy lamps are fed battery power through CKT 1732 and are grounded through CKT 745-- left front, CKT 747--left rear, CKT 748--right rear, CKT 746--right front. These circuits will ground through the door jamb switches. The courtesy lamp will be illuminated when the affected door is opened. For example, when the right rear door is opened, the right rear door courtesy lamp will turn on.

Not a fuse problem , if the BCM had blown fuse other thing's wouldn't be working as well . . Probably wiring or BCM . Using factory diagnostic,s instead of guessing as to what the problem is , is the proper way .

Interior Lamps Diagnosis
Symptom
Procedure
Important: Before proceeding with these diagnostics, check for DTCs. If DTCs are present, complete the associated diagnostics. If the condition still exists, return to this chart.
All of the interior lamps are inoperative when any door is opened.
Chart 1
The dome lamp is inoperative in the ON position, but OK in the door position. The map lamps operate normally.
The dome lamp switch is faulty. Replace the dome lamp switch.
The dome lamp is inoperative in the DOOR position, but is OK in the ON position.
Chart 2
The dome lamp is inoperative in any position and both reading lamps are inoperative.
Disconnect the dome lamp connector (BLK 3-way).
Check for voltage at terminal "C" CKT 1732 ORN wire.
If OK, the dome/map lamp is faulty. If no voltage is present, there is an OPEN in CKT 1732.
Either the right or the left sunshade mirror lamp is inoperative.
Chart 3
Either the right or the left rear reading lamp is inoperative in the ON or the DOOR position.
Chart 4
The rear reading lamp is inoperative in the ON or the DOOR position.
Chart 5
Battery rundown protection is shorted to ground - B1482.
B1482
The left rear reading lamp is inoperative in the ON or the DOOR position.
Chart 6