Speedometer
Thread Starter
CF Beginner
Joined: Jan 2020
Posts: 3
Likes: 0
Speedometer
2017 Tahoe 4 by 4 speedometer accuracy. I am trying to figure out how accurate the 2017 chevy tahoe 4 by 4 speedometer is from the factory. If it matters, this is the police version. Is/was the speedometer calibrated at the factory to show a higher than actual speed or spot on speed? Also, are there any materials from Chevy that explain this?
Super Moderator
Joined: Mar 2011
Posts: 9,175
Likes: 520
they are correct from the factory. If they were out if would effect odometer readings and they are federally mandated to be accurate.
if the tire and wheel size has been changed the speedo with be off. this can be corrected by changing the tire size in the ebcm. the dealer can do this or someone with a full function scan tool. you could also buy an aftermarket device that will correct this.
if the tire and wheel size has been changed the speedo with be off. this can be corrected by changing the tire size in the ebcm. the dealer can do this or someone with a full function scan tool. you could also buy an aftermarket device that will correct this.
Thread Starter
CF Beginner
Joined: Jan 2020
Posts: 3
Likes: 0
What is the federal accuracy mandate? Usually that would be expressed by a plus or minus percentage, and where might I find that? It seems it may be off as compared to GPS. GPS has a faster speed. Maybe the tires on the vehicle are wrong sized? What size tire was it originally calibrated to for the 2017 tahoe 4 by 4 police version?
Thread Starter
CF Beginner
Joined: Jan 2020
Posts: 3
Likes: 0
§393.82 Speedometer.
Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).That seems to be the only mandate I can find and it reads to be limited to commercial vehicles. And, it suggests plus or minus 10% which seems huge. Is there something else on this that explains how accurate the speedo is supposed to be from factory and the tire size that it is set to?
Super Moderator
Joined: Mar 2011
Posts: 9,175
Likes: 520
your truck has a tireplacard sticker located in the door pillar. Its states the original tire size and rim diameter. compare it to what is on the vehicle. if its different...that is your problem. the fix is either put on the correct sized tire/rims or recalibrate the ebcm as I have already mentioned.
in addition, the tcm uses vehicle speed as an input for transmission shift points...incorrect speed input will cause either delayed or premature shift points.
in addition, the tcm uses vehicle speed as an input for transmission shift points...incorrect speed input will cause either delayed or premature shift points.
Thread
Thread Starter
Forum
Replies
Last Post