My check engine light came back on yesterday and I am thinking it is primarily because of the P0504 code. I had the EVAP codes around this time last year but it went away after I wrapped some of the cracking hoses in some electrical tape. Any idea what route to go to check on the P0504 issue? I looked online and seems like it's either the switch itself or possibly brake lights but all my brake lights are illuminating. It is also probably time to replace some of the EVAP lines or possibly smoke test the system to find the leak.

Car Scanner ELM OBD2
Version: 1.112.3/1.112.3/iOS
DTC report
Connection profile: Lexus OBD-II / EOBD ~1999-2008 K-Line/KWP + extra sensorsDate: 10/21/2024 9:18:58 PM
============================
OBD-IIOBD-II
DTCs: 3
----------------------------
P0442 [0x0442]
Evaporative emission (EVAP) system - small leak detected
Evaporative Control Small Leak Detected
Status: Confirmed
----------------------------
P0456 [0x0456]
Evaporative emission (EVAP) system - very small leak detected
Evaporative Control System Very Small Leak Detected
Status: Pending
----------------------------
P0504 [0x0504]
Brake pedal position (BPP) switch A/B - correlation
Brake Switch A and B Correlation
Status: Confirmed

 

Hello,

A CEL would come up any time there is a Fault Code, regardless of its type.

P0504 - Brake pedal position (BPP) switch A/B Correlation, that's the first time I've seen this code frankly, it seems like at some point Toyota switched to a Redundant style Brake Switch, with Two opposing Switches in one Assembly, meaning that when you press the Brake Pedal, you activate Two separate Switches, where the Code indicates that they are no longer in Sync with each other. In your case, it appears that only One of the Switches failed and is no longer in Sync with the other, causing the Code, but not preventing the Brake Lights from working correctly. Interesting, and actually deeply ironic system, considering that it's the First time I've ever seen a Brake Light Switch fail in a Toyota, and it happened that one time they decided it requires Redundancy.

As for the EVAP Codes, your system has a Leak somewhere, seeing that it's a Small Leak, it's not something that will be easy to find just by looking at all the joints, your best bet would be to either purchase, or find someone with a Smoke Machine to find the source of a leak.

Hope this helps and best of luck!

 

Thanks for the explanation. I'll check if my code reader has data for those switches to confirm if one of them failed.

 

My OBD2 reader and iOS app does not display the info needed for that switch but I found a great troubleshooting diagram online for that code on the ES330. I should easily be able to rule out the switch itself using a multimeter.

 

@Arsenii I recently got gas for the first time since the check engine light came on and it went away right after that. Not sure if that is a clue as to what is failing or not. The car was not getting used much but we have started to need it recently and it is driven twice a week now. I did purchase a smoke machine on Black Friday so I plan on performing some tests over my Christmas break along with a ton of other maintenance.