Chrysler Repair: Chrysler check engine light, code 21, chrysler plymouth, plymouth acclaim

Question
You helped me in the past with the diagnosis by the number signal on the ignition key test.  My Chrysler Plymouth Acclaim 1994 model seems to be running fine,but the check engine light keeps coming on.  I recently had an oil change and added an additive to the oil which is supposed to help keep the valves from sticking open.  I lost power going up hill and stop to go before with that, so it seemed to help.  Other wise the car seems to be running fine, doesn't overheat or make any noises.  Wondering if you can tell me what the numbers mean on the ignition key test:  1-2-2-1-5-5
It seems to be something with emissions??
thanks for any help or advice you can give me.


Answer
Hi Jennifer,
The 21 is what is causing the light to be on. It says that your oxygen sensor is not putting out a signal either because of a broken wire or a worn out sensor. That is located on the exhaust manifold and can be changed out with the proper size box-end wrench (I believe it is a 21 mm but verify) and use some penetrating oil at the base to loosen it up overnight before you try to remove it. Warm up the engine for a few minutes and then rock the sensor back and forth gently with your wrench as you try to break the binding up of the threads and remove it slowly. Be careful not to burn yourself on the hot manifold. Also be careful not to damage the wires on the new sensor and use the grease on its threads that comes with it. Tighten it to about the same as a spark plug (18 foot-pounds). Take a look at the wires before replacing, but I suspect it is the sensor itself.
Roland