Check AIR pump to see that it comes ON when cold. The same 12v. signal for pump also feeds the AIR SOV. If No sig, check fuse.
If yes , then a common fault on that chassis is a broken vac line under the engine front cover. White, plastic line going to the AIR SOV under the cover [ cover just snaps up/off.]
If All looks well , then you want to check the 02 sensor. Air system uses the 02 to monitor if the AIR system is working by doing a self test and looking for an extra lean reading at 02..if sensor has lost the ability to read that low/lean, it will trigger AIR system as faulty even though it is not.
Problem is weak sensor in that case.
Common CTP code is there is not enough slack in the cable [ 1/4" ] at idle
or sticking cable..also check that you don't a a rug/mat bunched up at accelerator...
Cable is adjustable with turn wheel and lube it ...