Having the wrong number display when you press a number key isn't encouraging. Whether or not you're trying the wrong code, it shouldn't do this. Odds are high that it's a problem with a front panel connection, less likely to be inside the radio.

For the LCD display panel, did it display COdE, EEEE and OFF properly? If you press a 5 and see a 4 then it isn't a missing segment and if all the other digits are displaying okay then it likely isn't a display problem, plus it didn't like your unlock code when you pressed the correct button.

For keypad problems in general, a problem like this often suggests a problem with the keypad button/circuit board contacts being worn or dirty, a bit of dirt across pins on one of the LSI chips or connectors, or a loose or crooked front panel ribbon cable. Is the 5 button a preset button that was used often? If so then suspect wear and tear.

As a basic question, is your battery in reasonably good condition? If the radio isn't getting enough volts then the electronics may misbehave, including the keypad decoder. It would probably have to be pretty bad for that to happen, like under 10 volts.

First thing you want to do is disconnect the battery for a few minutes so the electronics and basic keep alive circuitry will reset.

Next you need to get rid of the lockout condition. I checked the owner manual and for yours, with the battery connected, turn the ignition switch to accessories on (KP-I), turn the radio on to get the OFF display and let it sit like that for two hours. Turn off other things like fans and lights (esp. the dome light and door markers) so you don't drain the battery. Turn the radio off and back on and you should now get the COdE prompt if it isn't there already.

There's a slim chance the keypad may now work properly if the electronics just needed a reset.

Beyond that, you will need to pull the radio. Before you replace it, you could attempt to see if you can fix it, but I wouldn't get my hopes up. I'd mostly be doing this for the satisfaction that as a DIYr I at least tried.

Check for a reset hole in the back or underneath. If present, connect the radio again to give it power and use a pin to attempt to reset it then try again.

Slam your hand around the radio turned in various positions in the off chance that dislodges a bit of dirt or dust or alters the display. If there are any gaps or holes around or near the front panel then you can try shooting compressed air in with the radio held upside down, also around those large front preset number buttons. An air compressor will have too much moisture, so use a can of compressed air (sometimes available in dollar stores as keyboard duster). Try it again to see if that made any difference.

Of course every time you try something you're one more step to having it lockout again and needing to do a two hour reset with the power on.

Next would be to open up the radio to attempt a bit of cleaning. At this stage you're into tiny screwdrivers and being careful to keep track of everything Remove the front panel to try blowing compressed air directly around the keypad. The front panel bezel may or may not come off without having to open up the radio so you can see the edge of the keypad and display boards to get some air behind them. If that doesn't work then you can try getting some spray electronic contact cleaner (not brake cleaner) around the keypad letting it dry thoroughly, but at this stage you can sometimes do more harm than good to the keypad contacts, so I might hesitate to do this. If that doesn't work then you can try removing the keypad board from the front panel to get some air and cleaner on the contact areas. In general, it's best not to clean any button or rubber membrane carbon contacts or scrub the circuit board contact areas so as not to wear the contact areas out any more than they already are, but you can scrub around any soldered connections with isopropanol. Carefully pull out and reseat any unsoldered ribbon cables. Blow it out dry, put it all back together and let it sit for a few hours before trying it again.

If that doesn't work then the radio is probably toast. If you're good at small electronics you could inspect the circuit boards for signs of a problem and attempt to check a few capacitors, but I think for a keypad display problem like this it may well be wear and tear on the keypad or dirt across some pins. At this stage it's probably not worth any further attempts at repair.

You can also poke around for Youtube videos hoping to find similar keypad problems and inspiration. For keypad problems, calculators are devices that people often try to repair. In the old days keypads were a lot beefier and could occasionally be repaired. Newer keypads are generally not repairable and many can't even be opened up to get to the keypad buttons and contacts.

Others here may have further ideas.

--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now