speedometer
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Joe28443
Joined: Jul 2009
Posts: 1,163
Likes: 4
From: Hampstead NC
speedometer
I went on a road trip this weekend and hooked the old garmin up. My speedometer is about 3 to 4 mph faster than the speed on the garmin. My truck is stock gearing and stock tires as far as I know. Which one do I believe?
Senior User
Joined: Apr 2009
Posts: 444
Likes: 2
From: Franktown, CO
Speedometer
This is probably not the simple answer you are seeking. This might not even be the right answer, but this is information that is useful. I am looking into the problems that most of us have with brakes. Namely brake shimmy. Everyone assumes that the problem lies with the brke rotors and/or pads. I am investigating the possibility of the antilock brke system role in this problem. Maybe a wheel speed sensor or the module itself. The Speedometer gets it's information from this system.
I will report my findings. It won't be anytime soon.
Speedometer
The instrument cluster is hardwired to the four wheel anti-lock brake system (4WABS) module. The instrument cluster micro-processor monitors the vehicle speed sensor (VSS) data from the 4WABS module and commands the speedometer with a corresponding movement of the pointer. The vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4WABS module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems that require a vehicle speed signal input.
I will report my findings. It won't be anytime soon.
Speedometer
The instrument cluster is hardwired to the four wheel anti-lock brake system (4WABS) module. The instrument cluster micro-processor monitors the vehicle speed sensor (VSS) data from the 4WABS module and commands the speedometer with a corresponding movement of the pointer. The vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4WABS module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems that require a vehicle speed signal input.
Senior User
Joined: Jul 2008
Posts: 171
Likes: 0
From: WI
Most vehicles read faster than actual ground speed in my experience. I've always thought that I keeps you going a little slower than you believe you're going, and it gives a few "fudge miles" for warranty. "Sorry, you're a little over on your warranty mileage, but we'll cover you anyway."
I have 55 series tires on our Focus when it comes stock with 50's, and the speedo is correct now. I have 285's on my X, and it's speedo reads correct. Would like to go to 235/85's next, and I'll have to have someone go in and change the conversion factor in the ECM.
I have 55 series tires on our Focus when it comes stock with 50's, and the speedo is correct now. I have 285's on my X, and it's speedo reads correct. Would like to go to 235/85's next, and I'll have to have someone go in and change the conversion factor in the ECM.
