Why is the odometer not working?

[PaulDella]

Sensor failure, loose plugs, and circuit breaks can all cause the speedometer and odometer to stop working. There is another type of fault where either the speedometer or the odometer works alone, indicating an internal circuit or mechanical issue in the instrument. Detailed inspection or replacement of a new speedometer/odometer may be required. Below is a related introduction: Composition: The speedometer and odometer are actually composed of two gauges—one is the speedometer, and the other is the odometer. Traditional speedometers are mechanical, typically connected via a flexible shaft containing a steel cable. The other end of the flexible shaft connects to a gear in the transmission. The rotation of the gear drives the steel cable, which in turn rotates a magnet inside the odometer's housing. The housing is linked to the pointer, which is set to zero by a hairspring. Overview: The odometer is a digital instrument where the transmission gear of the counter drum meshes with the worm gear on the speedometer's drive shaft, causing the counter drum to rotate. Its characteristic is that when the upper drum completes one full rotation, the lower drum rotates 1/10 of a turn. Like the speedometer, the odometer also has an electronic version, which obtains mileage signals from the speed sensor. The accumulated mileage data in an electronic odometer is stored in non-volatile memory, preserving the data even when power is lost.

[MacKai]

I've been repairing cars for over a decade, and when the odometer stops working, sensor failure is the most dreaded issue. The speed sensor is typically located on the transmission. If it gets clogged with sludge or fails completely, the dashboard won't receive pulse signals. Wiring problems are also common—rodents chewing through the wiring harness or loose connectors can interrupt the signal. Last time, I encountered an old Bora where the dashboard motherboard burned out, causing the odometer to stop counting—in such cases, the only solution is to dismantle the dashboard for repairs. I recommend first reading the fault codes to pinpoint the issue before rushing to replace parts. Before transferring ownership of a used car, pay special attention to whether the odometer functions properly to avoid future disputes.

[DeBraxton]

I once had an issue with my car's odometer not working, initially thinking the sensor was faulty. Upon inspection, it turned out the speed sensor's connector was severely corroded, with the wiring harness insulation cracked. These connectors underneath the chassis are particularly prone to moisture and oxidation, so it's best to check under the car after the rainy season. If the tachometer works normally while driving but the odometer doesn't move, it's likely a fault in the wiring from the speed sensor to the instrument panel. For older cars, it's also important to check if the fuse behind the instrument panel has blown. Avoid using high-pressure water jets directly on the chassis wiring during car washes to prevent many potential issues.

[AngeloMarie]

Just finished helping a friend with an odometer issue. The key is to first determine whether it's mechanical or electronic. Older cars with mechanical structures often fail due to a broken flexible shaft or stuck gears. Nowadays, most are electronic, and the most common failure point is the coin-sized vehicle speed sensor near the transmission. This part is exposed under the chassis and can stop working when exposed to water or mud. If all the needles on the dashboard are functioning normally but the odometer isn't moving, it's often due to a broken sensor signal wire. Cars with modified larger wheels may also have inaccurate readings due to changes in tire circumference, requiring a computer rematch.

[AuroraRose]

Three steps to diagnose odometer failure: First, unplug the vehicle speed sensor connector and measure the voltage, which should normally be within the 5-12V range; then check the corresponding 10A mini fuse in the fuse box; finally, inspect the wiring harness behind the instrument cluster. The easiest way is to use an auto shop diagnostic tool to read the fault codes—if the code relates to the vehicle speed sensor, simply replace the component. Last month, a car's odometer stopped working because the instrument cluster's stepper motor burned out—this requires removing the dashboard to replace the entire instrument cluster. Always drive slowly over potholes, as severe impacts can damage chassis sensors.