My husband has a 2002 dodge dakota 4 cylinders. We changed the battery out this morining and the map sensor bc it was cracked. Now it's turning over when you crank it but it eill not start fully and it is making a annoying squeaking noise. We had A tester put on it but its not throwing any codes off
If any codes were set previously, disconnecting the battery would have erased them. If you replaced the map sensor before starting the engine with the new battery, there is a new variable the Engine Computer hasn't learned yet so it doesn't know how to interpret the new readings. The biggest thing is it has to relearn "minimum throttle" before it will know when it has to be in control of idle speed. Until then you will have to hold the gas pedal down about 1/8" for it to start and stay running. You also won't get the nice idle "flare-up" to 1500 rpm when starting the engine.
To meet the conditions for the relearn to take place, drive it at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals. That may not work the first time because the high vacuum reading from the map sensor is what triggers the relearn to take place and the computer can still be interpreting those readings from what it thinks is the old sensor.