96 Eldorado trouble code PC 0420...
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 9 of 9
Northstar Engines and System Technical Discussion Discussion, 96 Eldorado trouble code PC 0420... in Cadillac Engine Technical Discussion; My dad's 96 Eldorado has the trouble code PC 0420 and the message "Service Emissions System" comes on the info ...
  1. #1
    AElayyat's Avatar
    AElayyat is online now Cadillac Owners Connoisseur
    Automobile(s): 85 Fleetwood Brougham, 90 Brougham 5.7, 05 Deville DTS
    Join Date
    Feb 2004
    Location
    So. Cali
    Age
    32
    Posts
    1,086

    96 Eldorado trouble code PC 0420...

    My dad's 96 Eldorado has the trouble code PC 0420 and the message "Service Emissions System" comes on the info center. The code came up 2 weeks ago, and the dealer cleared it and told my dad to drive the car around and if it comes up again to bring the car back to them. The code came up 2 days ago and this time I did what the dealer said; clear the code, make sure the gas cap is on tight, and drive the car around. The only thing I know is that this code has something to do with the catalytic converter. Any ideas of what I could check for before the car goes to the dealer. Sorry about the long post, but thanks in advance.

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    Ranger's Avatar
    Ranger is online now Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    70,383

    Re: 96 Eldorado trouble code PC 0420...

    P0420 - Catalyst System Low Efficiency
    There's a dead cat under your dad's car but before you take it in to be replaced, change gas stations if you always use the same one.

  4. #3
    AElayyat's Avatar
    AElayyat is online now Cadillac Owners Connoisseur
    Automobile(s): 85 Fleetwood Brougham, 90 Brougham 5.7, 05 Deville DTS
    Join Date
    Feb 2004
    Location
    So. Cali
    Age
    32
    Posts
    1,086

    Re: 96 Eldorado trouble code PC 0420...

    Thanks for that idea Ranger, I'll tell my dad to do so. I know that he ALWAYS runs 91 in the car.

    Another question for you Ranger, how many cats does the 96 Eldorado have? As I am not very familiar with this car (I know more about the 4.1 and 4.5).

  5. #4
    mcowden is offline Cadillac Owners Connoisseur
    Join Date
    Jun 2003
    Posts
    1,164

    Re: 96 Eldorado trouble code PC 0420...

    There is only one catalytic converter. There are oxygen sensors before and after it. If the change across the cat doesn't meet a spec, the 0420 code is set for low catalyst efficiency. It could be the cat, or as Ranger wisely suggested, it could be lousy gas. Try a different brand, different station, whatever to see if it keeps up. If so, the cat may need to be replaced. How does the exhaust smell? Does it smell distinctly like gasoline? (high hydrocarbons) Does it smell like rotten eggs? (sulphur)

    It's also possible an oxygen sensor failing or malfunctioning could cause that code without setting an oxygen sensor code. Whatever shop does the diagnosis should also test them to be sure that isn't the cause. An O2 sensor would be much cheaper to replace than the cat.

    Just my opinion. Let us know what you do and how it turns out. Good luck!
    Mike

  6. #5
    AElayyat's Avatar
    AElayyat is online now Cadillac Owners Connoisseur
    Automobile(s): 85 Fleetwood Brougham, 90 Brougham 5.7, 05 Deville DTS
    Join Date
    Feb 2004
    Location
    So. Cali
    Age
    32
    Posts
    1,086

    Re: 96 Eldorado trouble code PC 0420...

    Quote Originally Posted by mcowden
    There is only one catalytic converter. There are oxygen sensors before and after it. If the change across the cat doesn't meet a spec, the 0420 code is set for low catalyst efficiency. It could be the cat, or as Ranger wisely suggested, it could be lousy gas. Try a different brand, different station, whatever to see if it keeps up. If so, the cat may need to be replaced. How does the exhaust smell? Does it smell distinctly like gasoline? (high hydrocarbons) Does it smell like rotten eggs? (sulphur)

    It's also possible an oxygen sensor failing or malfunctioning could cause that code without setting an oxygen sensor code. Whatever shop does the diagnosis should also test them to be sure that isn't the cause. An O2 sensor would be much cheaper to replace than the cat.

    Just my opinion. Let us know what you do and how it turns out. Good luck!
    Thanks for the tips mcowden. I know that there is not a rotton egg smell but I think that there is a hint of gas smell. I'll have my dad pay close attention and see if he is noticing anything like that.

    I would rather have an o2 sensor fail because I know that the cat. converter for this car is expensive.

  7. #6
    mcowden is offline Cadillac Owners Connoisseur
    Join Date
    Jun 2003
    Posts
    1,164

    Re: 96 Eldorado trouble code PC 0420...

    I forgot to mention: When he checks for exhaust smell, the engine should be at full running temperature. So, he should give it a small sniff, say, when he gets back from the grocery store or something like that. If you just start it up cold and smell, it's going to smell like gas because the catalyst isn't hot enough to work yet. Certainly don't do it in a closed garage and don't stick your nose in the tailpipe. Waft a little up to your nose from the exhaust stream. If it smells gassy, it could very well be a bad cat.

    I think it's unlikely to be an oxygen sensor, but it's possible. New O2 sensors are around $60-$80 each for Bosch or AC/Delco. I've seen new cats for around $185, but I haven't looked around that much for those.

    Let us know how it goes with this...
    Mike

  8. #7
    AElayyat's Avatar
    AElayyat is online now Cadillac Owners Connoisseur
    Automobile(s): 85 Fleetwood Brougham, 90 Brougham 5.7, 05 Deville DTS
    Join Date
    Feb 2004
    Location
    So. Cali
    Age
    32
    Posts
    1,086

    Re: 96 Eldorado trouble code PC 0420...

    Mini Update:
    Today the code came back on in my dad's car. I did what the dealer suggested -- change the gas filler cap. I am suspecting that it is the gas station my pop is filling up at (Mobil). This is the second time for the code to come on with gas from this same station. My dad is still buring off the gas (3/4 tank left) he got from that station, so we will see what is going to happen.
    There is no smell of rotten eggs or gas from exhaust of the car -- so hopefully it is just the gas.

    I appreciate the help and suggestions you guys have offered, thanks.

  9. #8
    AElayyat's Avatar
    AElayyat is online now Cadillac Owners Connoisseur
    Automobile(s): 85 Fleetwood Brougham, 90 Brougham 5.7, 05 Deville DTS
    Join Date
    Feb 2004
    Location
    So. Cali
    Age
    32
    Posts
    1,086

    Re: 96 Eldorado trouble code PC 0420...

    Code poped up again yesterday (3-1-05). My dad called the dealer today and our service manager told my dad to replace the gas cap with an OEM unit not the aftermarket one. My dad is going to buy the OEM gas cap tommorow and we'll see how that goes. What do you guys think??? As always any help is appreciated, thanks.

  10. #9
    mcowden is offline Cadillac Owners Connoisseur
    Join Date
    Jun 2003
    Posts
    1,164

    Re: 96 Eldorado trouble code PC 0420...

    Yes, an 0420 can be a loose or bad gas cap. It can also be one of several solenoids that control the evaporative emissions system. Take a look at the canister. I believe on your car it's on the driver's side next to the gas tank. Make sure there are no cracks, etc. and that all of the lines to/from it are intact and in good condition. Look at the filler neck, particularly at any flexible parts of it, to make sure they are intact and no cracks, holes, etc.

    Basically it's telling you that the pressure or vacuum in the gas tank isn't what the computer thinks it should be. That's probably because something is letting air in or out where it shouldn't be. The gas cap is the easiest thing to check and fix, so it's a good start. After that, it's time to start looking for leaks.

    Hope that helps... Good luck and let us know what you do and how it turns out.
    Mike

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting