TheTallOne

(1990 ls400) I hit a bump in the road that was at the top of a hill and caused me to bottom out and since then my speedometer stopped displaying the correct speed. It appears to display about 30-40ish km/h below what the real reading is. It is only the speedometer and when the car is off or idling it drops to below zero. Is my gauge is borked or should I check my speed sensors? Nothing else appears to be damaged or not working that wasn’t already an issue. Any insight would be appreciated!

as99east

Most likely the cluster needs to be refurbed. They don’t take kindly to being bopped real hard and just wear out over time. Thankfully Speedo is easiest gauge to replicate with a GPS speed app on your phone etc, but I got sick of doing that and I’m kind of OCD anyway and just has my cluster refurbed by “the Lexpert”.

TheTallOne

Ah damnn I was hoping that wasn’t the case. It’s my daily for the next few months but I could send it off, I have an escort passport max that displays speed. Thanks for your response!

as99east

No problem. I was in your same position as I daily mine. The Lexpert aka Jim Walker was able to turn the repair around in 24 hours and it was a full cluster refurb.

Yamae

Your words "below zero" remind me the failed speedometer but "30-40ish km/h below" sounds like the worn gear of the speed sensor as is shown here. When the gear is wearing out, the speed signal is missing some and the speedometer shows slower speed.

I'd check the signal from the speed sensor using an oscilloscope. If it's not available, simply remove the sensor from the transmission and to check the gear visually is another choice. I have seen some of old Toyota cars having this problem.