You are being watched

My uncle replaced the engine with an old style old one

@Neoerectus What is the transmitter you want to disconnect?

@ArishMell The ecm for collecting data has a dedicated cellular connection, even if you do not have a subscription.

If you disconnect its antenna. it has virtually zero functionality. .

The car data is gathered and sold to data aggregators who will sell to insurance companies, etc. People online have already spoken of increased insurance rates from driving data obtained through these ecms.

These mechanisms often make use of the mics used for voice commanding. My Toyota has that "feature." Companies have the capability to eavesdrop on conversations in a vehicle.

In my Toyota, you cant remove it because it is integrated with the mic and one of the speakers

When you pay for "subscriptions," you negate their data gathering costs. I refused ALL subscriptions and under my state's privacy law have opted out of gathering and accumulation of data. My state's Att Genl Ofc has an ongoing issue with car companies not complying, however.

@Neoerectus I see. Thank you for explaining that.

What would worry me is if disconnecting the instrument would annull the insurance and any warrantee on the car, as an "non-approved modification"; perhaps larded with "and by an unauthorised person" (not a main or approved dealer).

That may depend on your national or State laws, but it would be a real risk in the UK. The "modification" and lost warrantee would not be illegal, but driving without at least third-party insurance certainly is.

If the insurer or its agent has unexpectedly stopped receiving data from a car still on its books, might it insist on investigating whether electrical fault or owner's act?

It would also worry me that the scheme might become extended to making the car undrivable if such features and subscriptions are not all working as the makers want.

.....

A wry note:

Perhaps you could test for eavesdropping by setting up a conversation with at least two passengers, in loud voices and describing the "features" in ripe language, about trying to switch it off.

@ArishMell So, others have disconnected with a modified connector (I bought one online referenced by an online group). My state law would back me in this as I understand things. I do not trust ANYTHING the current federal regime would or wouldnt do right now in the U.S.

In my research on the law, since this does not directly affect the engine, etc., they would be unlikely to be able to void warranties on operational aspects by current state law.

The fact they oft times remind one of servicing timelines at strategic times strongly supports they are getting the info, regardless of what cancelling "free trial data subscriptions" implied. My state has been wrangling with complaints against the car companies for this tactic.

Given they imply that not having a subscription stops data flow (in what I signed at purchase) is not a strong position for them should it have to go to court.

I have also made use of my state's privacy laws to lock down the 3rd parties collecting data (that I know of) as well (applies if those parties have 25k or more customers in the state).

Even CarFax buys that info and stores it. There are probably many that do so...
It may be futile, but I will keep trying to chase down the intrusions.

It could get messy,perhaps, but I am adamant.