Yamaha yfz r125 engine light on constantly, but engine runs ok

1. Faulty Instrument Cluster: The instrument cluster itself may be defective or damaged. Over time, electronic components can degrade, leading to malfunctions.
2. Fuse: Check the fuse box for any blown fuses related to the instrument cluster. A blown fuse could disrupt power to the cluster, causing all the gauges to fail simultaneously.
3. Faulty Wiring: There could be a problem with the wiring harness or connectors that supply power and data to the instrument cluster. Loose connections or damaged wires can prevent the cluster from receiving the necessary signals.
4. Vehicle Speed Sensor: The vehicle speed sensor (VSS) is responsible for providing speed data to the instrument cluster. If the VSS malfunctions, it can cause the speedometer to stop working, and it may affect other gauges as well.
5. Engine Control Module (ECM): The ECM communicates with the instrument cluster to provide data for various gauges. A malfunctioning ECM could disrupt communication and cause all the gauges to fail.
6. Grounding Issues: Poor grounding can lead to electrical problems, including instrument cluster malfunctions. Ensure that all ground connections related to the instrument cluster are clean and secure.

Given the complexity of diagnosing electrical issues, it's advisable to have a qualified mechanic or automotive technician inspect your vehicle. They can use diagnostic tools to pinpoint the exact cause of the problem and recommend the necessary repairs. Additionally, if the issue is related to the instrument cluster itself, it may need to be repaired or replaced by a professional.

For strangeness like that you need a good local auto electrician with a pro grade scan tool computer. It sounds like a BCM (body control module) communication issue.

https://www.google.com/search?q=auto+electrician+near+me

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If your speedometer stopped working and stays at 0 MPH, you should have your car checked ASAP. The most common causes of a speedometer that stopped working include are a faulty speed sensor, a broken gear on the speedometer, damaged wiring, or a faulty engine control unit.

If it is the speed sensor in the transmission, you should also have problems shifting and the check engine light should be on.
If it shifts normally, the speedometer has failed.

you may have a bad instrument cluster and on yours the BCM run the cluster not the PCM

LOOK AT THE RELAY GENERALLY A HOLE INSTRUMENT WONT GO OUT WITH OUT A FUSE BLOWING OR A RELAY THE HOLE THING IS ONE UNIT BUT RAN SEPERTLY

gm vehicles have alot of problems with the motors that run speedometer you can get instrument clusters at Murray's it is that common most instrument clusters are dealer only but these fail that much you can get them aftermarket.

Do you have a professional scanner ,do a scan of the whole vehicle . Instrument cluster , BCM , etc... Not OBD2 scan from autozone or advance etc.... thier tool can't check the whole vehicle network . The control module's on your vehicle all share information on what is called a serial data bus ,or communication network. ( temperature guage not working- sending unit keeps blowing, ) I don't think the sending unit is the problem , an it's not a sending unit . It's a engine coolant temperature sensor ,an it's a input to the PCM/ECM - engine computer . The engine computer send's this info. to the instrument cluster on the GMLAN data network . GM had problem's with stepper motors in the instrument clusters . The stepper motor control's the gauge needle.2003 to 2006
How to repair GM Instrument Cluster Speedometer Gauge Stepper

Also sounds like you have wiring harness issue's ,finding an viewing wiring diagrams an using a DMM - digital multi-meter to test affected circuit's is the way to a fix. Not guessing !


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Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model an engine size. Under system click on lighting ,then under subsystem click on headlamps . Click the search button then the blue link . Looking at the diagram you will see the headlamp / multifunction switch is a low voltage input to the BCM - body control module , do you know anything about automotive electronic's ? The high beams are contolled by a relay energized by the BCM . Check through some of the other wiring diagrams ,for the dash light's , pull the instrument cluster an check connection's ,power & ground circuit's etc...

tach is most likely a cam sensor, hvac could be a bad vacuum problem (bad hose ) the electrical (dash stuff) I would start looking for a loose or bad ground wire or dirty battery terminals

It may be a faulty speedometer with a short inside, or a short on speedometer wirings or connector.

Whenever car vibration cause the wiring to short, there you lose speedometer and trans functionality.

You need to access the speedometer connector and wirings to
instrument panel to fix this.