2007 Cadillac CTS have no brake lights. Power from switch to ABS module. All fuses are OK. Relay test OK.

Is the EBCM energizing the BAS relay to turn on the brake lights ?
The brake pedal position sensor receives both a 5-volt reference voltage and a low reference signal from the electronic brake control module (EBCM). When the brake pedal is pressed, a variable signal is applied from the brake pedal position sensor to the EBCM through the brake sensor signal circuit. The fuse block left rear supplies battery positive voltage to the bass relay switch through the BASS fuse. One side of the bass relay coil is permanently grounded at G402. The EBCM supplies voltage to the bass relay coil upon receiving the signal from the brake pedal position sensor. The switch contacts of the bass relay close and battery positive voltage is applied through the bass relay switch to the center high mounted stop lamp (CHMSL), and to the turn signal/hazard flasher module through the stop lamp switch signal circuit. The ground for the CHMSL is applied from G402. The turn signal/hazard flasher module then supplies voltage to the left and right stop lamps in the tail lamp assemblies that have ground at G401 and G402. For export vehicles the stop lamps receive battery positive voltage directly from the bass relay.

Did you have a qualified repair shop check for DTC'S - diagnostic trouble codes ?
DTC B3903 Stop Lamp Relay Circuit
The electronic brake control module (EBCM) supplies voltage to the BASS relay coil side voltage supply circuit when the stop lamps are active. The coil side control circuit of the BASS relay is permanently grounded at G402.

DTC C0278 Brake Pedal Position Sensor Not Calibrated
The brake pedal position sensor (BPP) is a potentiometer. The electronic brake control module (EBCM) supplies a 5-volt reference circuit and low reference circuit to the BPP sensor. The BPP sensor signal circuit is a direct input to the EBCM. The EBCM determines the BPP based on the voltage from the BPP sensor. The EBCM converts the BPP sensor feed back voltage to a digital signal and puts it on the class 2 communication bus.

DTC C0282 Brake Pedal Position Sensor Circuit Range/Performance
DTC C0283 Brake Pedal Position Sensor Circuit Low
DTC C0284 Brake Pedal Position Sensor Circuit High
DTC C0880 Device Voltage Reference Output 2 Circuit

Without knowing if any of these DTC'S are stored do not know what diagnostic direction to point you in .

Stop Lamps
The brake pedal position sensor is a resistive device used to sense the action of the driver's application of the brake pedal. The brake pedal position sensor provides an analog signal that will increase as the brake pedal is pressed.
The brake pedal position sensor receives both a 5-volt reference voltage and a low reference signal from the electronic brake control module (EBCM). When the brake pedal is pressed, a variable signal is applied from the brake pedal position sensor to the EBCM through the brake sensor signal circuit. The fuse block left rear supplies battery positive voltage to the bass relay switch through the BASS fuse. One side of the bass relay coil is permanently grounded at G402. The EBCM supplies voltage to the bass relay coil upon receiving the signal from the brake pedal position sensor. The switch contacts of the bass relay close and battery positive voltage is applied through the bass relay switch to the center high mounted stop lamp (CHMSL), and to the turn signal/hazard flasher module through the stop lamp switch signal circuit. The ground for the CHMSL is applied from G402. The turn signal/hazard flasher module then supplies voltage to the left and right stop lamps in the tail lamp assemblies that have ground at G401 and G402. For export vehicles the stop lamps receive battery positive voltage directly from the bass relay.

Do you know where the rear fuse box is ? Check BAS fuse 15amp. and the bas relay , should be marked on the inside of the fuse box lid . The rear fuse box is located

Fuse Block - Left Rear
In the passenger compartment, under the left side of the rear seat at carpet
Power and Grounding Component Views
Electrical Center Identification Views
Fuse Block - Right Rear
In the passenger compartment, under the right side of the rear seat at carpet.

If fuse and relay are ok your best would be to take to a cadillac dealer .

Kevin , this is a very complex way of stoplamp control , I will post GM service Description and Operation of how they work an let you deside if you want to tackle this ! Do the center high mount brake lights work ?
The brake pedal position sensor is a resistive device used to sense the action of the driver's application of the brake pedal. The brake pedal position sensor provides an analog signal that will increase as the brake pedal is pressed.
The brake pedal position sensor receives both a 5-volt reference voltage and a low reference signal from the electronic brake control module (EBCM). When the brake pedal is pressed, a variable signal is applied from the brake pedal position sensor to the EBCM through the brake sensor signal circuit. The fuse block left rear supplies battery positive voltage to the bass relay switch through the BASS fuse. One side of the bass relay coil is permanently grounded at G402. The EBCM supplies voltage to the bass relay coil upon receiving the signal from the brake pedal position sensor. The switch contacts of the bas relay close and battery positive voltage is applied through the bas relay switch to the center high mounted stop lamp (CHMSL), and to the turn signal/hazard flasher module through the stop lamp switch signal circuit. The ground for the CHMSL is applied from G402. The turn signal/hazard flasher module then supplies voltage to the left and right stop lamps in the tail lamp assemblies that have ground at G401 and G402. For export vehicles the stop lamps receive battery positive voltage directly from the bass relay.

There could be a code stored in the EBCM - electronic brake control module - DTC B3903 Stop Lamp Relay Circuit
DTC C0278 Brake Pedal Position Sensor Not Calibrated
there are several other codes that pertane to the brake lights . you could try Replaceing the bas relay !
Fuse Block - Left Rear
In the passenger compartment, under the left side of the rear seat at carpet.

Low brake fluid level could cause that. Bad ABS wheel sensor. Brake switch. Go to Autozone and ask them to put the scanner on and see what codes you're getting.

hi. does this sound familiar.

Anti Lock Brake System (ABS) problem. Has trouble code C1243.

1. Pin test power and ground to the Electronic Brake Traction Control Module (EBTCM).

2. Stress test the power and ground by using a high beam headlight or blower motor to put a load on the system.

3. If power and ground are OK, remove the EBTCM and hot wire the pump motor. If it runs OK and is quite, replace the EBTCM. If the motor is noisy replace both the Motor and the EBTCM.

2000 Cadillac Eldorado, ETC 4.6L, V8, VIN 9, USA *
Brake Pressure Modulator Valve (BPMV) - BRAKE PRESSURE MODULATOR VALVE WAS NEEDED

A failed brake light switch or brake light circuit fuse will cause BOTH problems. Start by verifying that the fuse is OK, then proceed with replacing the brake light switch if the fuse was not at issue.

Many of the master cylinders have connection for a brake light pressure switch. Some also active the brake lights by placing a switch directly under the brake pedal. You may need to build your own bracket.

ok about the abs is possible that the abs cable that goes the the brake caliper is not good.about the brake light check brake fluid level filled up also check the sensor on the brake fluid container also check any malfuntioning wire connection corosive plugs.about the ac check compressor ad freon in order to kick on check the relay or fuses or the compressor is no good

Take it to any local repair shop.

The ABS Relay,is for the system pump motor,nothing to do with lighting circuits.

Check brake switch !

Fuses are listed here

* = maxi fuse

1*=50A I/P fuse panel
2*=40A blower motor relay
3*= 50A 4 wheel ABS module
4*=20a Main light switch-Instrument cluster
5*=50A Ignition switch, starter relay

6*=20A Transfer case relay
7*= NOT USED
8*=20A Auto Ride Control Switch/on off switch
9*=40A Auto Ride Control relay
10*=30A PCM power relay

mini fuses
1=10A A/C relay
2=20A Aux power point
3= not used
4=15A Fog lamps-Daytime lamps
5=10A Air Bag diagnostic monitor
6=10A Powertrain Control Module (PCM)
7=30A 4WABS module
8=30A PCM relay
9=20A Fuel Pump relay and RAP module
10= 15A Horn relay
11=15A Park Lamp relay-Main Light Switch
12=30A Main light switch--Multi Function switch
13=15A Heated O2 sensors, EGR Vacuum Regulator, EVR solenoid,Camshaft position (CMP) Sensor,
Cannister Vent Solenoid, A4LD Auto Transmission
14=30A Generator-Voltage regulator


Interior fuse panel (mini fuses)

1=7.5A Power mirror switch
2=7.5A Blower motor relay,PAD module,Air Bag diagnostic monitor
3=7.5A Trailer tow connector
4=10A Left headlamp
5=10A Data link connector (DLC)
6=7.5A Air bag diagnostic monitor, Blower motor relay, Passive deactivation Module (PAD)
7=7.5A Trailer Tow connector
8=10A Right headlamp, Daytime running lamps (DRL) module, Foglight relay
9=7.5A Stop Lamp switch
10= 7.5A Speed control-amplifier assembly,Brake pressure switch, Generic electronoc Module (GEM)
Shift lock actuator, Blend door actuator, Main light switch, RABS resistor, A/C heater assembly
Flasher
11= 7.5A Instrument cluster, Main light switch, RABS resistor
12= 10A Power window relay, Washer pump relay
13= 20A Stop lamp switch, Brake pressure switch
14= 20A Rear Anti Lock Brake system (RABS) module
**10A 4WABS module**

15=7.5A Instrument cluster
16= 30A Windshield wiper Motor, Wiper Hi-lo relay, wiper run/park relay
17=7.5A Cig lighter
18=15A Drivers unlock relay-All unlock relay
19=25A PCM power diode
20=7.5A RAP module GEM module, Radio
21=15A Flasher (hazard)
22=20A Aux power socket
23=15A Turn signals
24===not used
25= 7.5A GEM module, Instrument cluster
26= 10A Battery saver relay, Electronic Shift relay, Interior lamp relay
Power window relay,Electronic shift control module, transmission control
27=15A Switch,DRL, Backup lamp switch, DTR sensor,Instrument illumination dimming control module
Dome/map lamp, GEM,electronic shift,Interior lights,Glove box lamp and switch
28=7.5A GEM module-Radio
29= 15A Radio
30=15A Park lamps, trailer Tow relay
31===not used
32=10A rear blower
33=15A Headlamps, DRL module, Instrument cluster
34=7.5A Rear integrated control panel, CD
35=10A RABS test connector
36=7.5A CD, rear integrated control panel, memory seat, Message center Attached images __________________