Working on a 95/96 s-10 blazer got a p19da code from obdll can you tell what it is.

no one can tell you any answers, you must have vehicle scanned for fault codes. Go to autozone for this.
All codes are OBDll and are available on line free
example P1105
P1105 Code - Manifold Absolute Pressure Sensor Malfunction

copy and paste
https://www.engine-codes.com/p1105.html


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p0540 is a OBDll code and codes cannot replaced. P0540 is an OBDll code and all are available online free.
google P0540 for more info or copy and paste
https://www.yourmechanic.com/article/p0540-obd-ii-trouble-code-intake-air-heater-a-circuit-by-valerie-johnston

Check the obdll code and it may tell you which cylinder is miss firing

What year is the vehicle ? Code what ? P0 what .

It is a fuel pump code, it means the computer is not getting a signal back from the fuel pump and the pump may be burnt.
Check the fuel pump relay for correct operation, if it is functioning then check the ground circuit. If you have vary high resistance, or no resistance then the pump is burnt and you need to replace the fuel pump.

drivers side under dash by knee plugs into the obdll port

The obdll code can only be reset by an obdll scanning tool. Did you repair the problem? If not the code will reappear & some mechanics will refuse to do repairs because they can not necessarily guaranty their work. The simple answer is go to a parts store, have them read the code, then have them erase it.

If your 1995 Chevrolet Blazer shows code P19DA, it means that there is a signal problem between the fuel pump and the PCM. This may have happened because you have a burned fuel pump motor, or the float meter of the fuel pump has a burnt wire.
Check the fuel pump relay, if malfunctioning, inspect the ground circuit to and see if the resistance is accurate. If it appears to be damaged, remove the fuel tank, taking out the pump, and replacing it with one that works.

Get the codes pulled, often an oil change place has all of the adapters. You need to know what the computer thinks is wrong, before you do anything.

it might but the obdll starts at 96 and up,but there is another conector under the hood on the passenger side for check engine codes.you can buy a ford code reader to do that with there about 50 dollars.if it does have the obdll it should be under the drivers side dash