P0504 Code

[lt538]

2010 Rt SM5 2600 miles.
My wife and I were riding in North Georgia, 20 miles from the cabin. The VSS light and check engine light came on. I turned off the Spyder, waited a few minutes, started to and the check engine light was on. Rode back to the cabin, after 10 miles, still running but no power to go up the grade. Left it on the side road to get the truck and trailer. I checked all the fluids . Starts and idles but check engine light is on. I get a P0504 code.
I added brake fluid. All brake lights are working. Battery was replaced April 2019. Checked positive terminal connection. It was tight. Any suggestions?
Dealer is 100 milestone way.

[jcthorne]

P0504 Brake Switch A/B Correlation

Check the brake lever switch. The other switch is the pressure switch in the brake line. ECU sees them switching out of sequence or one on when it should not be.

[Snowbelt Spyder]

Hey 538.
P0504 - Brake Signal Not Plausible. Brake signal vs brake pressure correlation check failed.

When you step on the brake pedal and actuate the Brake Light Switch, the ECM checks that brake fluid pressure is above some set point. If not, you get the code and limp mode. And the inverse is true, in that if you have brake fluid pressure, but do not have the brake light switch actuated, same thing happens. Now, this sounds similar to, but is completely different from the Low Pressure Switch function and logic.

99% of the time, this occurs because the rider is inadvertently holding their foot over the brake pedal and without knowing it, has pressed it down just far enough to actuate the brake light switch but not build up any fluid pressure in the system. Other times it's due to a sticking pedal linkage which is holding the brake lights on, or failed switch not operating the lights at all. So check for all of that. Clean and lube linkage. Check that the pedal comes all the way up every time and lights go on and off as required. Ask yourself could you have been riding the brake.

Remove the key tonight and let it sit. Ride tomorrow and do normal, positive braking. Let's see if the light and code clears.

Sometimes, folks have added a helper spring to the linkage. Others have needed the switch replaced. If your brake lights are not working at all, replace the fuse for that first. All depends on what you find out. Good Luck.

[lt538]

Thanks for the reply. I will do what I can before a trip to thedealer

[MrMagicFingers]

Excellent replies guys!

I look forward to what the OP with the issue has to say after some time has set in.

This is what forums are supposed to be about!

Tim

[lt538]

I cleaned and lubed the linkage. Brake lights are off and on with pedal action.
Check engine came on at start up and stayed on. I rode about 10 miles, limp home light came on, engine went into lump home mode. Put it on the trailer and took it home.
Still showing P0504 code.
Next trip is on a trailer to the dealer.

Thanks for your help