The flashing up shift arrow notifies you that there is something wrong with the transmission. Initial guess would be the PNP switch finally wearing out. To verify, with the engine off: move the gear shift to R, then "row" the shifter from R to L about 20 times. Put it in P and start the engine. The shift light should have gone out and you will be able to drive normally for a period of time.

I have no idea what 2 hoses you are refering to, are they thin vacuum lines, which side of the engine, up front by the radiator or next to the throttle body? I also do not know why you added ATF to the tranny when you replaced the radiator. Any ATF in the old radiator would be a minescule amount.

When you are on a budget, you can go to most any auto parts store and ask them to read the codes for you - free. California does not allow for erasing the codes.

Your check engine light should also be on, verify that the bulb is not burned out when you turn the key to position II.
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My name is Klaus and I am a V♂lv♂holic