Hello: Going to explain this to the best of my ability.. To start, my vehicle is a 2000 Saturn SC2 with around 170k miles. The first thing that happened was my Service Engine Soon light came on, code reads "P0410 Secondary Air Injection System Malfunction." Code stayed on for a while, then symptoms began, which were that my idle was high, around 1500 to 2000, intermittently, seemed to happen more frequently after I took my car on the freeway. Also, it may be worth mentioning that the temp gauge reads colder than normal instead of being in the middle after the car warms up. Could be relevant or not. But the main problem is the high idle, while in neutral, putting my car in gear drops the idle back down. Any thoughts on this issue appreciated
Current status as of now: The SES light is off now, but idle issue persists, at dealership for the 3rd time now.

 

P0410

Electrical Schematic Attached


P0410 diag video by a guy that knows his stuff


HIgh idle:

If temp gauge on dash is reading lower, check ECTS in head. This temperature sensor provides indirect feedback on engine temperature which in turn affects the air-fuel mix.

Do NOT continue to take it to a dealership that repeatedly charges you for diag fees and fixes that do not solve the problem.

You can check and if necessary replace this sensor and connector for $40 in 10 min.

Once you find the sensor (driver's side two-wire in cylinder head with a squeeze to release witing harness), remove the connector and measure the resistance across the two pins of the sensor.
Measure it on a cold engine.
Measure it on an operating temperature engine (do not burn yourself).
You may need to insulate all but the tiniest portion of your meter leads to keep them from touching.

Please post the Resistance readings

Also, check for signs of corrosion on the connector, green or otherwise. This measurement is done across a small resistance (when hot) so any corrosion can skew the measurement into appearing that the engine is cooler than it really is.

 

Derf:

Thank you for your reply and your assistance on this matter. As of now, the issue seems to be resolved and has not re-emerged since I brought it back to the dealership. I do regret taking it in to the dealership in the first place, the reason I did was because I thought it was an issue that would ultimately end up at the dealership because of how complex it was. Anyways, I appreciate your reply, and if the issue re-emerges, I am going to take screenshots of what you wrote and save the diagram because it is valuable information to have on hand.

 

It's all good.

What all did they find fix or replace?
I ask so that this post can be closed out with a resolution for those that visit later on in time. There is nothing more frustrating than finding a post identical to your issue where the resolution was never posted.

Thank you.