I forget when and how my speedometer stopped working but I took it in to a Lexus dealership to diagnose it. Keep in mind that my brake booster also hasn’t been working where the accumulator was not that weird noise.

Luckily, they fixed the speedometer and decided not to charge me. The representative said the mechanic mentioned the electrical ground was pretty rusty and after cleaning it, speedometer was up and running again. My mistake was not asking for details but i was more surprised that the service was free. After driving out of the parking lot, the brake booster accumulator was also pumpin again.

i wasnt sure if the brake booster noises were relevant but i had to mention it since coincidentally the speedometer and brake booster were both actively working again.

does anyone know which ground the mechanic may have been referring to? Also, im assuming this specific ground will resolve my speedometer issues..

 

the following error codes were triggered in my prev post. I just cant figure out which ground needed cleaning… https://www.clublexus.com/forums/gs-...er-issues.html

 

The brake booster, on these cars, is a part of the ABS module assembly. The instrument panel control module gets the speedometer feed from the ABS module, more specifically from the rear wheel speed sensors. Not sure which ground said mechanic might have cleaned, but if a ground is bad, the ABS module will not operate as appropriate and will enter a safemode to prevent short-circuiting. Once the ground is regained, the ABS module will continue as normal, giving the speedometer a signal again and turning the brake booster back on.

I personally prefer vacuum brake boosters, much less maintenance and if one does go bad, much easier and cheaper to replace. Plus they give a little better of pedal feel, but that's just my opinion.

 

Front speed sensors are 1.6kOhms and rear speed sensors are 1.1kOhms. I wasn't sure if the rear sensor values are within normal range. I reset DTCs but response from speedometer. The GS400 never went into safemode. I am not sure how to determine whether the ABS module is functioning but this situation was the same before the dealership resolved everything...

I'll look into vacuum brake boosters, thanks