Fuel additives

Have a 00' GP with 3.1. Recently had the CAT changed and at the next fuel up I added a fuel additive to clean the injectors. Yesterday, I got a 0420 code for catalyst efficiency below standard - bank 1. Can an additive set this off? Is this the O2 sensor setting this off? Also, I was advised by the dealership that 2 of the coil packs were going. Can bad coils cause this 0420 code as well. I'm replacing the coils today. Thanks for any advice.

Have a 00' GP with 3.1. Recently had the CAT changed and at the next fuel up I added a fuel additive to clean the injectors. Yesterday, I got a 0420 code for catalyst efficiency below standard - bank 1. Can an additive set this off? Is this the O2 sensor setting this off? Also, I was advised by the dealership that 2 of the coil packs were going. Can bad coils cause this 0420 code as well. I'm replacing the coils today. Thanks for any advice.


The P0420 code is generated by the 02 sensor after the CAT. In your case you got a new CAT. When I replaced my CAT, I installed new 02 sensors (fore & aft) just for general principle.

The error might clear out once your run the additive and tank of gas out and run through a few drive cycles. Although P0420 may trigger a SES light, its not a serious error code. My odb-ii scanner shows that type error as pending.

BTW - If your coil packs are confirmed bad probably a good idea to get them replaced too. Good luck!

hey just a little extra input.....

when i was at goodyear getting my discounted oil change :grinyes:

i was talking to the machanic about those additives and he told me because of the set up of our injectors and exhaust manifold that sh*t you put in your gas will not fully burn and it can clog up by building up a gunk near and around the exhaust manifold.. thats what i was told and i belive it because it makes sense... because of how cheap that additive is, it can't be that great. just get a good tune up and replace the injectors if they are screwed up!!

just my opinion!

- short

Well, my dad, who is a retired ASE certified master tech who worked at a GM dealership for the past 12 years (And a dodge/chrysler/plymouth one the 20-some-odd years before that) told me that they're worth adding, that they can't hurt the car, and could save you a bit of money in the long run. I don't think they should be added with every tank, but I usually go for once a month or so.

Well, when I had my car into the dealership I was told by their service rep that the diagnostics on the car showed the car needed to have the injectors cleaned. The car has been running fine and got 30 MPG during a recent trip. So I figured using a top end additive to clean the injectors would be a lot less expensive job. I've not had anymore codes come up since the coils were replaced and it has all kinds of horsepower. I really like this car, too bad the wife gets to drive it. :( Thanks for all the advice too.