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Brake lights not working 2008 Rav 4 T180 4.3


Mark O
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Perhaps a complex problem so bear with me here please! Essentially the brake lights do not work. I also have the ABS and brake warning lights on at the dashboard. I believe the ABS or VSC - anti skid??? share a circuit with the brake lights, and that when an open line is detected the ABS and brake warning lights come on.

I have managed to acquire the fault codes 46 and 49 which seem to indicate that it is brake light fuses, brake light switch circuit, brake light relay, brake switch, ABS/traction control actuator.

So trying to proceed logically

Fuses 2 x 10A ---OK

bulbs - both OK

Brake light switch - OK

Brake light/stop light control relay - basic 5 pin relay in box- does not seem to check out. As I understand things, there should be pretty much no resistance between pins 4 and 3 as voltage feed normally comes in from the brake switch to pin 4 of the relay and out to pin 3 and then to the lights. There is actually high resistance or an open line. Aha I hear you say, and therein may lie the fault - BUT- there is only 2V at pin 4 when the brake switch is actuated. I assume - maybe incorrectly - that this should be 12V for the lights? There perhaps should also be 12V at pin 5 - when the ABS energises the relay  - again less than 2V. I am confused!

I have ordered up a second hand relay ( £2.50 ) so that may answer -  I refuse to pay the 100 quid the stealers were asking! 

If the relay does not cure things, any advice as to where to look next would be most welcome.   

 

 

 

 

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Try resting the ABS. If you have a fault on the ABS so you need to resolve this first. Swapping electronic parts for used is never a good idea.

Check brake fluid level but could also be a faulty ABS sensor or wiring or even ABS module itself. If you are only getting 2V at the switch are you testing between +Ve and a good earth? Verify the earth by testing continuity between 2 two good earth points such as the chassis and a ground wire. I would also get the correct Brake / ABS circuit wiring diagram for your car. ABS faults can be tricky so good luck.

https://www.rav4world.com/threads/reset-abs-light-without-taking-to-a-garage.305883/

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It is not clear if I have a fault on the ABS. It is clear however that I have no brake lights, and also clear that if there is a fault there then that affects the ABS warning lights as the shared circuit detects an open line and warning lights come on if there is an open line.

 I checked the voltage at the pins from the pin across to the negative of the Battery, but for sure it could be a poor earth - somewhere!   

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Some progress. I have nothing at the brake switch so it suggests a poor connection between the fuse and the switch. The only thing in that circuit is the connector itself. I have a diagram of where the connector is, but it is not at all clear - connector a38 I think. Any help most appreciated as to how to proceed.

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On 10/3/2021 at 6:51 PM, Mark O said:

Some progress. I have nothing at the brake switch so it suggests a poor connection between the fuse and the switch. The only thing in that circuit is the connector itself. I have a diagram of where the connector is, but it is not at all clear - connector a38 I think. Any help most appreciated as to how to proceed.

http://www.trav4.net/stop_light_switch_circuit-945.html

Have you checked the relay IG2? If that is faulty you wont get any volts at the switch. Check the coil resistance of the relay

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