1989 low mileage 244. I have a check engine light, which I think I may have caused by not fully indexing the gas cap. With the cap now properly installed, I still have the light. Is there a reset for that light?

You need to use the diagnostic socket under the hood to determine the diagnostic code(s) associated with the event(s) that triggered the Check Engine light.

As much as you have a 240, your '89 B230F engine uses the same LH 2.4 fuel system, ignition system and OBD (diagnostic) system as the 700/900s of that vintage. To determine the associated diagnostic code(s), go read here in the 700/900 FAQ
https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

You need to check both the #2 (fuel system ECU) and #6 (ignition system controller) sockets for up to 3 codes each. You can repeat the code reading as often as you want until you do a code reset.

In the OBD code tables, there are hints as to the reasons and systems that might be involved. From there you do traditional diagnostic testing and problem isolation.

Once you've read all the codes, you do a reset to make the Check Engine light go out. The reset procedure is described there (do it on both ports), or you can simply disconnect the battery for a few moments.

Normally, if the problem isn't apparent, you can do a reset, hoping the problem was transient. Sometimes that's the end of it, but often not. If the Check Engine light soon comes back then you know you've got a lingering problem that needs to be identified and dealt with.

The severity of the codes determines whether it's reasonably safe to keep driving with the light on, but in general it's best to keep engine operation to the absolute minimum until you know what's going on.

Look up all the diagnostic codes on both ports and post back if you need further guidance.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi,

I don’t think in 1989 that the OBD was that sophisticated to monitor the gas tank pressures in relation to the cap being loose.
Emission checkups only tested the cap and the tank line from it to be pressure tested manual from the evaporative canister under the left side of the front bumper.
The fix was the seal on the cap, the line from the fill pipe up to the vacuum operated tee on the canister.
There’s no sensor at this time of smog checks to accomplish keeping the technician honest.
Because they weren’t honest or diligent we had to get that added on to our car prices.

A code for or of too a rich or lean mixture is a catch-all for vacuum lines being bad.
This along with other issues can be considered fun and games but not insurmountable.
That code is like a “shot gun blast” at being “diagnostics” that hits a wall of a barn. You have to go looking up and down, from end to end, of the whole barn or in this case the car.

It is a known issue for the rubber lines to that canister up to the engine to be rotten badly by this age car.

Have you read the black box? It has a blinking LED light inside it under the hood. It’s up by the brake vacuum booster area.
There are simple instructions, in service manuals like Bentley, to guide you through reading up to three codes in memory.
I think it’s three in my memory? (:-)

Punch in OBD codes into the FAQ for 700-900 search box it might take you out somewhere.

Others can help get you on the right highway to finding the issue.

My browsers or something in the site has stopped me from taking a peek at your profile to how long you have been posting or what state you are in to help you more.
If you are a newcomer or the site is down in that area, we have trouble linking prior posting issues to diagnose what the problem might be.

I hope it get fixed in that it’s a helpful tool.
Information in troubleshooting is always quicker.

Phil

a loose gas cap won't set the light on that car. that code came with the 96-up cars.