Intermittent speedometer issue

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Apr 1, 2021 | 07:00 AM

FioreFire

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Joined: Jul 2020

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Intermittent speedometer issue

I just bought a 2001, V10, 4WD Excursion, and am very excited to fix it up. The speedometer has an issue where it intermittently dips down to 50MPH when I'm driving between about 60-70MPH, then jumps back up to the actual speed one second later. I plan to take a look at the speed sensor and maybe clean the contacts, but I want to see if anyone else has had this issue and fixed it before I potentially move on to buying a new speed sensor.

Apr 1, 2021 | 07:44 AM

wae

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Joined: Mar 2005

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The problem could also be on the output side of the equation. I'd try to isolate if it's getting the wrong speed from the VSS or if there's a loose connection or solder joint on the cluster first. Get an OBD2 scanner that can show live data or a ELM327 bluetooth/wifi dongle and the Torque app for your phone and bring up the ECU's vehicle speed PID. Keep that up on your scanner or phone and drive the vehicle. When the gauge cluster dips look to see if the scanner also dips. In fact, I think you have have it graph the vehicle speed for you so you can look to see if it blips. If the speedometer is dropping but the ECU is reading a steady value, then you have an output problem from the ECU to the cluster. If both are dropping then you have a problem with the VSS or its wiring to the ECU (probably a loose or bad ground, if I had to guess).

Apr 2, 2021 | 10:23 AM

wpnaes

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Joined: Nov 2010

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From: N. IL

Does it only happen in wet weather?