Causes & Fixes for a Broken Speedometer
Blown speedometer fuse If you have no other symptoms beyond the speedometer not doing anything, it’s likely that the fuse responsible for powering the speedometer has simply gone bad. Additional symptoms: None. You might get an error code or warning on your dashboard if you drive a newer vehicle. The repair: This is an easy DIY job if you’re handy. Refer to your manual to find the fuse diagram for your vehicle. Pop the hood and open the fuse box. Locate the fuse for the speedometer and remove it. Hold the fuse up to a light to see if the wire inside is broken. If it is, replace the fuse. If the fuse is fine, replace it and continue troubleshooting. Cost to fix: A new fuse shouldn’t cost more than $5-15. If you have a mechanic do this for you, it’ll likely cost $100 or so.
Faulty speed sensor There are multiple speed sensors in most vehicles. The two that might trigger a speedometer to not work without any other symptoms are the transmission speed sensor (which monitors the transmission’s rotational speed) and the ABS speed sensor (which checks your tire rotation speed). If either sensor dies or fails, your speedometer dial won’t move. Key note: This is a distinct component from the vehicle speed sensor (VSS). While a bad speed sensor isn’t a huge deal, a bad VSS is a major automotive issue. We just want to make it very clear these are two different components, since mixing them up can be catastrophic. Additional symptoms: If the transmission speed sensor fails, your cruise control may not work. A bad ABS sensor may keep the ABS system from working. Other than that, you’re unlikely to have any other symptoms. The repair: See a mechanic to have the troubled sensor replaced. Cost to fix: A new sensor and installation shouldn’t cost more than $100-300.
Faulty vehicle speed sensor (VSS) The VSS is a third key speed sensor in most vehicles. It’s in the transmission and is responsible for monitoring and controlling the rotational speed of the crankshaft. If the VSS goes bad, your speedometer may fail alongside some other noticeable issues. Additional symptoms: Your transmission will likely behave erratically, your check engine light will come on, and you’ll likely experience engine misfires, poor mileage, poor engine performance, or engine stalls. The repair: The VSS needs to be replaced. The difficulty here is that the VSS is often (but not always) located inside the transmission, and accessing it can be very difficult. Cost to fix: The cost will range anywhere from $300-2,600 depending on how hard the VSS is to reach.
Broken speedometer gears On (mostly older) vehicles, there are gears just behind the speedometer dial that engage and turn to physically move the needle. If one of those gears breaks or the grooves in the gear loose their shape, your speedometer may not work properly. Key note: This can happen on modern cars, but it’s extremely rare. You’re more likely to run into bad speedometer gears if you’ve got a car made before 1995 or so. Additional symptoms: Usually, none. You may hear weird clicking noises behind your speedometer, though. If the gears are partially intact, the speedometer dial may move erratically instead of not moving at all. The repair: The dashboard needs to be disassembled so you can swap out the gears on the speedometer. If you’re a gearhead, give this a shot yourself! Otherwise, see a mechanic. Cost to fix: It really depends on the make and model. This is unlikely to cost more than $100-200, though.
Damaged cable wiring The speedometer is largely an electrical component, and if one of the wires responsible for the circuit has frayed, been chewed on by a squirrel, or degraded naturally over time, the speedometer may not work. Additional symptoms: You may not have any other symptoms. Depending on the cable’s connection, your speedometer might turn on and off intermittently. The repair: The wire likely needs to be replaced. See a mechanic to have a pro do this one—electrical work is pretty dangerous if you aren’t trained on it. Cost to fix: It depends on how much work is involved. It shouldn’t run more than $200-300, though.
Bad ECU The engine control unit (ECU) (also known as an engine control module, or ECM) is basically your vehicle’s main computer. It monitors your engine and relays that information to the rest of the vehicle so that everything runs smoothly. If the ECU malfunctions or begins to fail, it may impact your speedometer’s ability to interpret the data it’s receiving. Additional symptoms: It can vary depending on how bad the ECU is. On the minor side, you may just have a check engine light. On the more serious side, you could have electrical issues, vehicle stalls, trouble starting the vehicle, and bad engine performance. The repair: See a mechanic to have the ECU replaced. Cost to fix: You’ll likely pay $1,000-1,5000 for a new ECU.
Bad instrument cluster control panel (digital only) If your speedometer is digital, it’s tied into the instrument cluster control panel’s system. The instrument cluster control panel is basically the motherboard for your dashboard lights. It controls and monitors the dash lights and sensors. If the panel dies or malfunctions, it can mess with the speedometer’s performance. Additional symptoms: A bad instrument panel will likely cause other dials and warning lights to misbehave or shut off. At worst, your entire dashboard won’t turn on. The repair: See a mechanic to have them replace and rewire a new instrument panel. Cost to fix: It depends on the make and model of your vehicle, but it can run anywhere from $200 to $1,500.
Troubleshooting Tips
Use your manual to locate the fuses and wiring diagrams. If you do plan on doing any electrical work on your vehicle (which we don’t recommend if you aren’t a gearhead), use your vehicle’s manual to locate the fuse map and wiring diagrams. That’s the only way to confirm that you’re actually tinkering or working on the correct components.
Plug an OBD-2 sensor into the OBD port to narrow the issue down. Get an OBD-2 reader and plug it into the OBD port underneath your steering wheel. Start the vehicle and press the “scan” button on the OBD reader. The results may help you narrow down where to start looking for the problem.
Replace the fuses first when in doubt. Compared to all the other potential issues with your speedometer, a blown fuse is not only the most likely culprit but it’s the easiest potential repair. If you’re planning on doing some DIY work on your car, start by checking or replacing the fuse just to rule it out.
Can you drive without a speedometer?
Generally, yes, although you may accidentally speed. If your check engine light is on or you notice any symptoms interfering with your ability to handle your vehicle alongside your speedometer problems, do not drive. But if your speedometer is the only issue, it’s probably not going to interfere with your ability to drive. Just be careful—it’s easy to speed when you don’t have a speedometer giving you a precise reading. Just use common sense if you’re going to drive without a speedometer. Don’t push your engine, go slow, and stay with the flow of traffic.
In some states, it’s illegal to drive without a speedometer. With some exceptions for historic vehicles, many states and cities have restrictions on driving without a speedometer for safety reasons. If you are thinking about driving without a speedometer, look up your local laws first before you drive.
What to Do if You Need a Speedometer ASAP
Use your phone temporarily as a speedometer. If your speedometer goes out in the middle of a long drive and you can’t reasonably stop, at least pull over and download a speedometer app on your phone. The app will use your phone’s GPS coordinates to get an estimate for your speed. This will at least give you some idea of how fast you’re going. The speedometer apps are not nearly as accurate as the speedometer in a car. Go at least 5–10 miles per hour (8.0–16.1 km/h) below the speed limit just to give yourself a cushion and margin of error.
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