: P0121, P0507 High Idle???

01-13-08, 05:23 PM
Whats up?
I have a 2005 deville base model that is acting wierd. It idles high, at around 1500-2500, almost like a sticky gas pedal, but under the hood with the engine running, I can physically feel that the throttle is all the way closed. It is throwing me the p0121 and p0507 codes. Is this a TPS problem? My Deville is still under warranty, but if its a simple fix, I would rather do it myself. The dealer will probably just fill me with B.S. and not only that, he will take a week to 2 weeks to do it. I dont want to be without my caddy for more than a day or 2. If I can find out whats wrong I will do it myself. Thanks Guys

P.S. YES I have cleaned the TB out with cleaner. and tried the "throttle relearn" process, both with no progress... :(


01-14-08, 06:42 PM
Well, thanks for nothing guys.
I made an appointment to see the dealer tommorow.
Hopefully I can get my car back sometime this century.

Crown Vic Owner
01-14-08, 06:47 PM
Shouldnt they give you a rental?

01-14-08, 07:24 PM
The ECM is not getting a signal from the throttle for the p0121 code, the p0507 is usually related to the fuel pressure regulator. These aren't perfect but at least you now know what to expect from the dealer and will be able to discern if they are actually solving the problems or just clearing the code and hoping it goes away. I found this at cadillac p0121 (http://www.forumdig.com/search.aspx?q=P0507+cadillac) and there is more to sort through if you want to become more knowledgable on it.

01-14-08, 07:34 PM
Sounds like maybe a vacuum leak. The plenum (rubber coupler between the TB and manifold) seems to be a rather common leak point.

01-14-08, 07:53 PM
I asked for a rental and was denied one. I am taking it to Joe Self Cadillac, the only Cadillac dealer in Wichita, KS. They informed me that they dont have loaner or rental cars. Anyways, I am just upset because my Deville only has 30,000 miles on it, it shouldnt be acting like a car with 130,000 miles on it. :banghead:

I just hate messing with dealers, your chance of them getting it right is 50/50, maybe they will fix it right the first time, maybe they wont.

I shall pray to the Cadillac Gods and hope they smile in my favor.

Crown Vic Owner
01-14-08, 07:55 PM
id be looking for another dealer myself.

01-14-08, 08:06 PM
I thought you are ENTITLED to a loaner when it (Cadillac) is under warranty.

I hear you about the 50/50 thing. Going bad for the 3rd time tomorrow morning to get things fixed that were damaged during a warranty repair. :bomb:

Crown Vic Owner
01-14-08, 09:02 PM
I dont think you are if you are under 25

01-14-08, 09:06 PM
Well, I am 28 yrs old, and I thought I was entitled to a rental as well. But I just want it fixed. Hopefully all goes well.

01-15-08, 03:31 PM
Well it turns out that I am indeed entitled to a rental car. I was given an 08 Pontiac G6 as a rental. I was saying all the way home "I want my Deville back, I want my Deville back" LOL I mean, come one, you have to MANUALLY set the heater and A/C, and the seats are like child seats or something, really small and absent of leather. Also, as I was driving my caddy to the dealer I also noticed that not only was the idle high, but it refused to downshift as well, even at full throttle. Anyways, its there baby to deal with now.... I just hope it gets fixed. Till then, Ill be big pimpin in a black G6...lol:histeric::thepan:

01-15-08, 08:53 PM
I was given an 08 Pontiac G6 as a rental.
Don't feel too bad. I was given a Chevy Cobalt today. I forgot how to operate crank down windows and manual two way seats. Looking forward to getting my baby back tomorrow. Hope they don't screw it up this time.

02-03-16, 02:06 AM
Is there a way to test for vacuum leaks in general and that may be related to the plenum?

02-03-16, 10:37 AM
Simply spray Brakleen, TB or carb cleaner or such around all the vacuum connection with the engine idling. For the plenum duct, flex the bottom portion while spraying. Any RPM increase indicates a vacuum leak.