Brake System Warning Light (yellow) sporadically coming on

[tekkie]

Hello members,

Car info:
2018 Leaf SL
Mileage: ~80Km (~50Kmiles)
Extended warranty: 120Km or up to Apr, 2024

Hoping you can provide some inputs if you have come across this issue. I have the Brake System Warning Light (yellow) coming on and stayed on once in while. This happens when I turn on the car and releasing the electronic hand brakes. I cannot reproduce this issue at will and for the past 2 months, it happens about 6 times now. If I turn off the car and then turn it back on, the warning light goes away. The car drives and stops normally. I change the brake fluid and service the brakes annually as recommended by the manual.

I brought the car to Nissan dealer and this is what I got back. The tech did some analysis and showed me a scope reading indicating that there is an issue with the RH electronic brake module. However, he cannot determine if it's the module that is malfunction or if there is a break in the wire and further analysis is required. I paid $178 CAD for the first diagnostic and they want another $500+ CAD for further analysis because it is estimated at 4-5 hours of work. This just sounds like extortion to me!

My car has extended warranty, but this is what the dealer said. If it turns out to be the electronic brake module defect, then all cost will be covered. If it's a wire breakage, then I have to pay for all analysis cost + labor to fix it (~$800 CAD). I turned down the further analysis and paid the $178 for the initial diagnostic to do more research. The dealer also said, if I decide to bring the car back and if it turns out to be the electronic brake module, then they will reimburse me back the $178 that I paid.

If you have some suggestions/guidance for me on what I should do next, it will be greatly appreciated. I have a mechanic that I have been using for my ICE vehicles for over 15 years; can a competent mechanic be able to find out if the issue is at the electronic brake module vs broken wire?

 

[goldbrick]

Are the modules reversible? If that is possible you could have the mechanic swap the modules to determine if it's the wiring or the module itself that is bad.

Otherwise, maybe try to check the signals at the module when applying the brake but I don't know if the average mechanic could do that. It would help that the other side works so maybe there is a way to compare what happens between right and left on the various wires or even rig up some wiring adapters to 'swap' sides to see if the failure follows the module or the wiring.

 

[tekkie]

[ It would help that the other side works so maybe there is a way to compare what happens between right and left on the various wires or even rig up some wiring adapters to 'swap' sides to see if the failure follows the module or the wiring.
[/quote]

The scope reading from Nissan tech showed both the Left and Right readings of the e-brake modules and the RH one has part of the signal missing. This was how the tech determined the issue was with the RH module. Not sure why he cannot determine if it's the wire issue by checking the signal right at the module.

 

[goldbrick]

That does seem odd, maybe they want to leave all options open since there is still some uncertainty.

With no direct exposure to the problem, it seems unlikely that 'some signal' would get through a bad wire. Even if the signals in question are CANBUS data I'd expect a bad automotive wire to either be open or shorted to ground, etc. Wires/cables can degrade and cause signal integrity loss, but I can't remember seeing anything of that nature in all the car forums I've been on over the last many years (excepting the obvious case of spark plug wires, which are somewhat unique and not relevant here).