TPS Code 21 88 5.0 RWD
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 3 of 3
5.0 and 5.7 Discussion, TPS Code 21 88 5.0 RWD in Cadillac Engine Technical Discussion; well..the check motor light comes on..passed emmissions after a cat was changed and a tune up..but light came on..showed ox ...
  1. #1
    Blotto is offline Cadillac Owners Member
    Join Date
    Mar 2006
    Posts
    9

    Question TPS Code 21 88 5.0 RWD

    well..the check motor light comes on..passed emmissions after a cat was changed and a tune up..but light came on..showed ox sensor..changed that then I changed the EGR...now i get this TPS code 21 light and it was changed a few mts back..muffler guy said it was running a bit rich....vacume lines seem to be ok..all is well the car is running well except the idel is a bit too high..but not when a/c is on and in gear..will changing the TPS again put a stop to this madness?...thanks for your help...

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
    Automobile(s): 94 Fleetwood Brougham
    Join Date
    Aug 2004
    Location
    Rockford, IL
    Age
    47
    Posts
    7,489

    Re: TPS Code 21 88 5.0 RWD

    Check evap emissions system, if it is getting fuel up from the tank or canister it will run rich. Disconnect the lines and plug at the canister. Look for changes.

    The thing to check to determine if the computer is making it run rich is to monitor the M/C solenoid dwell. It should be close to 50% duty cycle. If not, the ECM might be commanding it rich. Then you have to figure out why. Cold coolant temps, or cold as the ECM "sees" it will make it run rich.

    Don't get into the thing trying to throw a bunch of parts at it to fix. Too many mechanics do that now. If it is running rich, RARELY is the O2 sensor the issue, that indicator is the O2 is READING rich. Sorta like replacing the monitor on your computer because of a error on the computer. It won't go away long term in almost every case.

    Evap emissions will cause it to run rich, but to determine that is the culprit, you ~should~ see the M/C solenoid duty cycle railed commaning lean, trying hard to fix it. If it isn't, it is NOT evap emissions.

    Look for plugged PCV, bad wires/cap/rotor/plugs to, they will contribute, but are often not the main problems. BUT if one is really bad, it would see way rich and the M/C solenoid would pull back way lean and the other cyls would run lean, but the one not firing would still be passing raw fuel compunding the problem.

    If the duty cycle is ok (50%) and it is rich, then and only then would I consider O2 sensor bad, but only after a lot of testing and ensuring it is in closed loop mode and engine hot, and after run down the highway for 5-10 miles at higher rpms or so to ensure it is fully warmed up.

  4. #3
    Blotto is offline Cadillac Owners Member
    Join Date
    Mar 2006
    Posts
    9

    Re: TPS Code 21 88 5.0 RWD

    Thanks NODIH..well I did a complete tune up a few days ago..plugs wires rotor and cap..and installed a cat..all to pass emmissions....since o2 sensor was old i went ahead and replaced it so its new..and also the egr is original so i replaced it..not at too much expense..the TPS code 21 is the one i get now its not all the time just here and there..this wed im looking a it and will preform the checks you suggested..I did put a 4 row radiator in it a few yrs back..so it does run cooler..that may be the problme..car runs great a bit under powered but its smoothe and gets a whopping 12 MPG....NODIH I think what you described is , if not all, part of the problem...I have considered putting a happy face sticker over the check light..(smile)....the car passed inspection with flying colors..since I had a shop replace the TPS a yr or two back it has not been the same....more discussion form anyone will be helpful..in fact we can discuss it over a few beers while you work on this thing in my garage..(just kidding, but its a thought).....later Blotto

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