Chrysler Repair: 2.5L 4cyl tbi idle problem: are fault codes related?, exhaust gas recirculation, battery clamps

Question
I have a 1994 Dodge Shadow, Standard, 4 Cyl. 2.5lt when I start the engine and heats about 1 min the RPM meter goes from 900 that i think its the normal operation to 800, 700 and so on like its going to turn off and i get this check engine light sequence : 1-2-2-1-3-3-1-5-5-1-5-5, I was wondering if you could point me in a direction of what this means, (whats wrong with the car), someone told me that this codes was about the speed sensor and the oxygen sensor but im not really sure

Answer
Hi Alfredo,
The 12 means that sometime in the recent past the battery was disconnected, but usually this is not a problem unless you really have not disconnected the battery that you can remember in which case it might mean you have a loose connection at the battery clamps.
The 21 means that the oxygen sensor has stopped working...so unless the wires at the tip are broken you may want to change out that sensor.
The 33 means there is a problem with the A/C compressor clutch circuit
The 15 says that the speed sensor circuit is not sending a signal (your speedometer should not work if that were the case).
The 51 is another oxygen sensor fault, so that is duplicative of the 21.
So your information was correct, but not complete.
I don't see a basis for the idle speed drifting down. You might want to check the exhaust gas recirculation (egr) valve which is located behind the engine, near the firewall, and closer to the front of the engine to see whether the valve stem in the saddle shaped opening is moving freely when you try to move the valve stem back and forth with the tip of a screwdriver that is inserted in the slot of the stem. If it seems to be lazy (spring action should close it firmly) then lubricate the stem where it enters the body of the valve.
Perhaps if you replaced the oxygen sensor the mixture would adjust better, but that usually doesn't come into play within a minute after you start the engine.
The other thing you should try is to carefully remove the air cleaner houaing (noting all the hose attachment on the underside and front and side of it) to gain access to the throttle body. Then open the throttle butterfly valve and use solvent to clean the throat of the valve opening, both sides of the plate that constitutes what is called the "butterfly", and the passageway at the side of the throat opening that is used for idle air bypass. If that plate, throat, or passageway are dirty it can cause problems with the idle. So do that and check the egr valve and see if that helps with the idle control. Then consider getting a new oxygen sensor which probably won't help the idle but should make the car get better gas mileage and have less pollution and pass the smog test with a better margin of safety.
Those are my suggestions. Good luck on these relatively minor maintenance issues which when completed should solve the problem.
Roland