chiffon jackson

What was your result?

Cindy Aull

If the brake lights aren't working when the fuse is good and brake light bulbs are the correct type, everything else working, could the relay still be bad?

ruley73

Yes, the relay could still be bad. You should also check the plug that connects to the bottom of the underhood fuse block for corrosion or a weak connection. You could also have a bad brake light switch at the pedal. In any case more troubleshooting is needed.

Cindy Aull

how do you suggest how I go about troubleshooting? Thanks

ruley73

You first need to establish what exterior lights are/aren't working, and go from there.

Do all the tail lights still work fine?
Are all of the brake lights not working including the 3rd brake light at the top of the liftgate?
Do all the turn signals work (both front and back)?
​​​​​​​Do the sidemarker lamps still work (both front and back)?

Cindy Aull

[QUOTE=ruley73;455786]You first need to establish what exterior lights are/aren't working, and go from there.

Do all the tail lights still work fine?
Are all of the brake lights not working including the 3rd brake light at the top of the liftgate?
Do all the turn signals work (both front and back)?
Do the sidemarker lamps still work (both front and back)?[/QUOT
only the brake lights aren't working, even 3rd brake light. Turn signals (both front and back) work, taillights work, and side lamps are working.

ruley73

Did you check the CHMSL/DM/LAMP fuse (fuse #22 interior fuse panel, 15A)? This fuse is for the Center High Mount Stop Lamp (a.k.a. third brake light), but none of the brake lights will work if this fuse is blown because this circuit is used to close the relay for the other two brake lights when the brake pedal is pressed.

If the CHMSL fuse is good, the most likely cause is that the brake pedal position sensor is either unplugged or no longer working and needs to be replaced. Yes, this part is actually is a sensor with a variable signal and not just a simple on/off switch like older vehicles used to have. A replacement part costs under $10 and is fairly easy (albeit very awkward) to replace. However, you will need to take the vehicle to a shop to have the BCM learn the resistance values new sensor after replacement. This procedure requires a capable scan tool that you most likely don't have. Because of this, I highly recommend that you confirm the sensor is in fact not working if at all possible before replacing it and paying a shop to finish the job.

1. Remove the black panel for access to the brake pedal sensor and connector. It's held in place with two 7mm screws, one at each rear corner.

2. Turn the ignition key to the RUN position then back to OFF to wake up the BCM.

3. To test the brake pedal position sensor, use a voltmeter to check for presence of a signal coming from the sensor. Leave the connector is plugged into the sensor. Touch the voltmeter's red probe to terminal B (middle terminal with dark blue wire) and firmly press the black probe to a clean, metal grounding point. You should see the voltage fluctuate somewhere between 0-5 volts DC. The voltage should increase as the brake pedal is pushed closer to the floor. As a point of reference, on our Equinox the voltage is about 0.75V DC without pushing the brake pedal at all, and increases to 1.5V DC with the brake pedal pushed down as far as I could with the engine off (while holding the test probes in place ). If you see any voltage fluctuation when pressing the brake pedal with the test probes placed as described, the switch is probably fine. If you see no voltage (open circuit) or 5 volts with no fluctuation (sensor is shorted), the sensor is probably bad, but you need to first confirm that the sensor is receiving the 5-volt reference signal from the BCM if you see no voltage.

4. Unplug the three wire plug that goes to the white brake pedal position sensor.. You'll first need to remove the gray locking clip before you can unplug it.

5. Touch the red test probe to terminal C (gray wire; 5-volt reference), and firmly press the black test probe to a clean, metal grounding point. You should see a reading near 5 volts here. If so, this part of the circuit is good and the ground coming from the BCM (aka "low reference") should be tested. If not, the BCM isn't working properly or you have a wiring problem in this circuit that requires further troubleshooting.

6. To test the low reference/BCM ground, leave the connector unplugged, touch terminal C (gray wire) with the red probe, and use the black probe to touch terminal A (orange wire with black stripe; low reference/ground). You should also see a reading near 5 volts here. If so, this confirms the ground coming from the BCM is also good. If no voltage is observed, the BCM isn't working properly or you have a wiring problem in this circuit that requires further troubleshooting.

If everything tests good in steps 5 and 6, replace the brake pedal position sensor and immediately take the vehicle to a shop to have the BCM recalibrated. The GM/AC Delco part number is 13597428 for all 2007-2009 Chevy Equinox/Pontiac Torrent models.

Please make sure you post back again if this fixes your problem.