Esc and tach
Electronic Stability Control is one of the futures controlled by ABS module. It will help vehicle to get stable on the road in conditions like under-steering or over-steering and not only. If the ESC switch is not pushed to turn the system OFF and the light comes ON on dash during driving the vehicle, this condition indicates a malfunction of this system. The easiest scenario could be that your brake light switch is shorted out (yes... brake light switch). It is directly incorporated into this system because is connected to communicate with ABS module and it is one of the most common problems found in Hyundai vehicles. Any kind of diagnostics must be done by Hyundai dealer. After market locations (non Hyundai dealers) do not have proper equipment to communicate with ABS module software.
ESC is the stability traction control. It should be on by default every time you start the car. ESC helps when you lose control like slippery roads. The cars computer will take over and brake and accelerate according to the needs to prevent you from spinning out(too a point). Why they have an off button? Some situation like snow, the wheel will spin and that is normal, but the ESC will set the brakes on slow the accelerator and you can only can go like 10 mph. So one need to turn off the ESC to override the computer to go.
I would check the instrument cluster by taking it out and checking the rear 2 connectors for well seating. Maybe you can look at the circuit board for burnt out components at the tacho meter, however doubtfull.
Ignition Failure Sensor drives the tach... follow wiring from coils off back of cylinder toward the throttle body direction,, on the stamped steel plate, you will find a black plastic overgrown computer chip looking piece with 2 bolts holding it to the plate.. Usually a stocking item at both Hyundai and Kia,, will run approx $90 for the part.
The source for the instrument tachometer is the Ignition Detection Module. It goes to the ECM where it is labeled as the Ignition Detection Input and leaves that input pin to travel to the dash indicator. It enters the dash via connector M15-6, pin 6 on a pink or white wire with a black tracer. See attachments for visual association of what I am writing. If the tach signal out of the ECM is steady at the DTL connector, it would be safe to assume the signal is getting to the ECM and not the instrument cluster. You might try to disconnect and reconnect the connector plug on the back of the instrument cluster to ensure good connection. Worst case, you may need to ohm the wire from the ECM that runs to the cluster. The ECM connector might need a good visual inspection as well. Do not get too hung up on the terms ECM/PCM, they do the same thing. The primary difference here will be in the type of transmission you have. The ECM is used with manual tranny and PCM is used with auto transmission vehicle. If only the tach is acting up, you most likely do not have any fuse issues, however, if other instruments or anomalies exist, there may be a power issue in the instrument cluster. There are some recent threads on how to remove the instrument cluster, so give it a go. Good luck.
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