Why is my hold light on?

The "Hold" light on a 2003 Mitsubishi Montero typically indicates an issue with the transmission's hold feature. This feature allows the transmission to remain in a selected gear for longer periods, usually beneficial for driving in conditions like steep inclines or towing. If the "Hold" light is illuminated, it could signal a few potential issues:

Transmission Fluid Level or Quality: Low or dirty transmission fluid can cause the light to turn on. Check the fluid level and quality and replace or top up as necessary.

Transmission Sensor or Solenoid Issues: Faulty sensors or solenoids in the transmission can trigger the Hold light. These components are responsible for controlling gear shifts and fluid flow within the transmission.

Transmission Control Module (TCM) Problems: The TCM controls the transmission's operations. If there's a problem with this module, it might cause the Hold light to come on.

Wiring or Electrical Problems: Damaged wiring or electrical issues can also cause the Hold light to illuminate.

Mechanical Issues within the Transmission: Internal mechanical problems can trigger the light, though these are typically more serious and may be accompanied by other symptoms like slipping gears or unusual noises.

So, the first thing to do is check the transmission fluid and if okay I would service the transmission. Here are generic guides to help you step by step with instructions in the diagrams below to show you how on your car:

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

and

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

Fluid Types
Transmission fluid .................... DIAMOND ATF SP III or Equivalent

Capacities
Automatic Transmission fluid .................... 9.7 L (10.2 quarts)

Check out the images (below). Please upload pictures or videos of the problem so we can see what's going on.