4Lo Blinking, Unrelated DTC (P0504)

[encrypttie]

Hello everyone,

Here's another 4Lo blinking thread! I read some of the other ones but looks like in all cases they all have DTCs.

What I experiencing is this: 4Lo is off when I turn on the car. A couple of seconds to a couple of minutes after driving it starts blinking (no other lights, only 4Lo) and keeps on blinking until I turn off the engine. I live in Seattle area, so it's wet and cold here - in case this information is useful!

What is puzzling me is this:
1) There are no active DTCs, except for a P0504, which is Brake Switch A/B Correlation Code.
2) I can switch to 4Lo and 4Hi no problem, even if the light is blinking.

The 4Lo was constantly blinking before, I cleaned the hot spot in the actuator. Since then I am getting this strange behavior.

I appreciate your help in advance!

 

[encrypttie]

I figured it out. Even tho P0504 seems to be unrelated to the transfer case, it's the code that's causing 4Lo to blink!

I verified by clearing the code, and pressing the brake pedal which caused P0504 to be thrown, and the 4Lo start to blink.

Hope this helps anyone who comes across this in the future.

 

[TeCKis300]

Thanks for this thread and it gave me enough clues to fix my similar issue.

Symptoms​

No blinking at startup. Seemingly random triggers of 4Lo fast blinking during driving, at which point it won't stop blinking until the next startup cycle. No functional symptoms. Issue started as blue moon occurrences on longer drives, getting more frequent and uncorrelated to any types of use or driving conditions. Other than being triggered upon braking.

Issue​

Reading codes, confirmed it is P0504, which is Brake Switch A/B Correlation Code.

In layman terms, it means the brake switch behind the brake pedal is providing inconsistent status versus another internal braking switch reference that is likely within the ABS booster/system. The external brake switch is what triggers the brake tail lamps so that function is somewhat safety critical in nature. Don't ignore this issue, especially if you are towing.

CAUTION - This is absolutely safety critical for towing as trailer brake controllers rely on this tail lamp switch. To then apply proportional braking. These controllers won't engage the trailer brakes if it can't detect that the brakes are being applied, which is dependent on this switch.

Fix​

Replace "Toyota Switch Assy, Stop Lamp" - 84340-69075

Amazon.com

1 banana job, 10 minutes

Removal​

Cliff notes: unplug harness, turn whole body of switch counterclockwise

Install / Adjust​

 

[HiFiGuy]

I have the same 4LO light, but mine comes on about once a week, probably every 4th-5th time I start the car, and says it has to do with a "small leak" in the vacuum/evap system.

 

[TeCKis300]

I have the same 4LO light, but mine comes on about once a week, probably every 4th-5th time I start the car, and says it has to do with a "small leak" in the vacuum/evap system.

Yes, there are multiple causal issues to cryptic blinking lights. This one is specific to the brake switch. If you're lights blink in different fashion or combinations, it's not the same issue. Reading codes would be an important step to isolating actual issues.

 

[encrypttie]

I have the same 4LO light, but mine comes on about once a week, probably every 4th-5th time I start the car, and says it has to do with a "small leak" in the vacuum/evap system.

Make sure the gas tank cap doesn't have any cracks and its tight. For me it stopped throwing that code after I cleared the codes and stopped overfilling... I used to fill even more after the pump clicked off, which caused that leak error for some reason. Not sure what's causing your error tho.

 

[encrypttie]

Thanks for this thread and it gave me enough clues to fix my similar issue.

Symptoms​

No blinking at startup. Seemingly random triggers of 4Lo fast blinking during driving, at which point it won't stop blinking until the next startup cycle. No functional symptoms. Issue started as blue moon occurrences on longer drives, getting more frequent and uncorrelated to any types of use or driving conditions. Other than being triggered upon braking.

Issue​

Reading codes, confirmed it is P0504, which is Brake Switch A/B Correlation Code.

In layman terms, it means the brake switch behind the brake pedal is providing inconsistent status versus another internal braking switch reference that is likely within the ABS booster/system. The external brake switch is what triggers the brake tail lamps so that function is somewhat safety critical in nature. Don't ignore this issue, especially if you are towing.

CAUTION - This is absolutely safety critical for towing as trailer brake controllers rely on this tail lamp switch. To then apply proportional braking. These controllers won't engage the trailer brakes if it can't detect that the brakes are being applied, which is dependent on this switch.

Fix​

Replace "Toyota Switch Assy, Stop Lamp" - 84340-69075

Amazon.com

1 banana job, 10 minutes

View attachment 3649736

Removal​

Cliff notes: unplug harness, turn whole body of switch counterclockwise
View attachment 3647285

Install / Adjust​

View attachment 3647288

Thanks for posting this. I also ended up replacing the switch with a new one after I figured out what's causing the issue and it solved the problem.

 

[HiFiGuy]

Make sure the gas tank cap doesn't have any cracks and its tight. For me it stopped throwing that code after I cleared the codes and stopped overfilling... I used to fill even more after the pump clicked off, which caused that leak error for some reason. Not sure what's causing your error tho.

I did buy a new factory Toyota gas filler cap, and I don't overfill, making sure to stop when the auto-stop feature on the hose stops the flow. If it's truly a vacuum leak, as the code says, it might just be a journey of discovery.

 

[TeCKis300]

I did buy a new factory Toyota gas filler cap, and I don't overfill, making sure to stop when the auto-stop feature on the hose stops the flow. If it's truly a vacuum leak, as the code says, it might just be a journey of discovery.

Sounds to me this is a completely different issues, more related to the evap/charcoal canister. How the dashboard conveys these issues is completely obtuse. Why it choose to quick flash 4LO for the brake switch, or a slow flash 4LO for an emissions issue related to the evap canister, who knows. But I'm 99% sure you're chasing something different.

This thread might help you more

Search results for query: evap canister

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