Check Raised Brake Light?!

[geoff]

For an '05 Carrera tip with 60+K miles: Today driving back from getting my right rear tire patched with multiple 2" screws sticking all the way in to against the wheel, the "Check Raised Brake Light" warning came on intermittently on the dash display. Then it would go out. I wasn't pressing the brake when it happened. Only one did the red exclamation mark appear on the dash display, and when I checked the OBC, the Info option said "Check 3rd Brake Light". I drove to my local dealer, and checked the brake lights with my service advisor - all were good. So I drove back to the head mechanic, who spent about half an hour trying to figure out what was going on, and thought it might be a loose connector. I'm going back next week with some contact cleaner for him to pull things apart. Besides a loose connector, is there anything else we should be looking at? No codes or stored errors showed up in the PIWIS. Everything seems to work fine, but it's always annoying to get warning messages when driving!

[Loren]

Loose or corroded connector is probable.

Perhaps even a bad light panel.

[geoff]

Loose or corroded connector is probable.

Perhaps even a bad light panel.

Thanks Loren. We thought it might be a loose connection somewhere, since it was intermittent and the warning came on even though I wasn't pressing on the brakes. The mechanic didn't have any contact cleaner in his cabinet full of spray cans, so I'll bring some with me next week. All the lights in back lit up with the brake pedal pressed - what can go bad on the light panel? No code showed up for PIWIS, even though at one point the red exclamation lit up on the dash - should it have.

[Loren]

Intermittents are hard to trace simply by their nature. It would not surprise me that you don't see any codes on PIWIS - you would likely have to do some drive link tests and visually verify what does and does not happen.

If you can't find any bad connections then try re-programming the rear light controller.

[Sand8]

Intermittents are hard to trace simply by their nature. It would not surprise me that you don't see any codes on PIWIS - you would likely have to do some drive link tests and visually verify what does and does not happen.

If you can't find any bad connections then try re-programming the rear light controller.

Question: the "rise" brake light is the one on the spoiler? This brake light only active (on) when the spoiler is up, and when the spoiler is up, the "fixed" 3rd brake light is not active (off), correct? Thanks.

[geoff]

An update: I took the car in to the dealer, spent a few hours with the mechanic trying to track down the problem. The brake light that raises up on the spoiler was a little loose, so he popped it out, added some felt pads, carefully routed the wire harness and pushed it back together. He also cleaned the contacts on the wire harness connector to the raised spoiler and reprogrammed the rear module controller (to fixed spoiler and then back to standard moveable spoiler). According to my wife, the problem now occurs more often than before! Any other suggestions of what to try before spending money replacing parts? All the lights in the brake panel appear to be working just fine

[Loren]

Check the X23 disconnect in the engine compartment - rear right side.

Sometime water and dirt get in those and the pins corrode.

If that is know t be good then the next connectors are in the passenger compartment under the left rear side panel. Check those for damage too.

After that the wires just go to the cluster (no other connectors.

[wwest]

For an '05 Carrera tip with 60+K miles: Today driving back from getting my right rear tire patched with multiple 2" screws sticking all the way in to against the wheel, the "Check Raised Brake Light" warning came on intermittently on the dash display. Then it would go out. I wasn't pressing the brake when it happened. Only one did the red exclamation mark appear on the dash display, and when I checked the OBC, the Info option said "Check 3rd Brake Light". I drove to my local dealer, and checked the brake lights with my service advisor - all were good. So I drove back to the head mechanic, who spent about half an hour trying to figure out what was going on, and thought it might be a loose connector. I'm going back next week with some contact cleaner for him to pull things apart. Besides a loose connector, is there anything else we should be looking at? No codes or stored errors showed up in the PIWIS. Everything seems to work fine, but it's always annoying to get warning messages when driving!

The cruise control system monitors the 3rd, high mount, brake light in order to cancel CC if voltage is applied. To check for circuit integrity there is a "keep-alive" resistor that always supplies a fixed level of current flow to the high mount bulb(s). So if the bulb goes "open" even momentarily that will be detected and CC will be disabled. The use of LED bulbs is now common but must be compensated for by used a parallel resistor of the correct size to simulate the actual incandescent bulb filament resistance which is VERY low prior to illumination, full 12 volt application.

I used a 12 volt relay and a 50 watt halogen bulb to defeat the CC monitor. With the relay not energized the bulb is connected through the NC contacts but with relay activation only the lED bulbs remain in the circuit.

If you replace burned out bulbs in the high mount brake light be sure to use the correct bulb wattage as replacements.

[geoff]

Another update: I took the car back to the dealer the other week, since the error message was showing up more frequently (although not on the way to the dealer). The head mechanic and I went through the wiring diagrams, checked out all the connectors and went as far as sanding the contacts on the ground lugs behind the rear seats. Then we plugged the car in to the PIWIS and found the stored coed 8034 - third brake light. The fault symptom was: open circuit. We also found the error code 9470 for the additional brake light. Not very informative, but we started going through the automated fault diagnosis procedure, and got to the step where possible problems were listed. One of the possible problem causes listed was a faulty brake pedal switch, and the mechanic said they had a lot of problems with them failing on the early 997s, but nothing causing this error. Since it was a known problem component and the part was less than $25, we decided to go ahead and replace the switch. After over a week with the new switch, the error message hasn't returned, and I'm keeping my fingers crossed that this actually fixed the problem. I'll post again if the error returns. For reference, the part number for the new brake pedal switch was 996-613-113-02