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code 21 check engine light............. Now a code 24

T

tonkatruckon44s

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My 88 suburban is pulling a code 21 and i can figure out what it is i already tried changing the tps. What step is next.
 
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I can hear the fuel inside three truck it sounds like a faucet I'm not sure why its using so much fuel.j think I'm going to try to swap computers between it and my k5 today we will see what that does
 
Not sure swapping the ECM is a great idea. Probably won't hurt anything, but those computers are programmed for the different engine/transmission setups. So even if the original code goes away, it may set several other codes.

And, some of those codes might prevent the original code from occurring.

I would check the wiring going to the tps. The unit is powered by a 5 volt power supply. A short to from the output to that supply would cause that code.

Also a bad ground to the sensor would cause that, since its just a variable resistor to ground.
If the ground reference goes away, the computer is going to see the full 5 volts which will set the code.
Look at the connector real close. and the wiring.
 
Sorry i have been typing on my phone so i havent been able to give a lot of info. now i am at a computer so i hope that telling the whole story helps. i got this suburban 3 years ago it had a 97 chevy 350 vortec installed with a edelbrock carb intake manifold and edelbrock 750 carb. the truck always starved itself for fuel so i only used it for short trips. this summer my friend wanted to take all his TBI stuff off and wanted a carb so we swapped carb for tbi, i got the adapter and checked all the connectors to make sure they all were there. every connector was there except the injector connectors so i just spliced some new ones to the existing wires and everything has worked great. the check engine light was on but i didnt think anything of it because i had been on for 3 years. So then i parked the suburban since august until friday and friday i drove ten miles and went through almost an 1/8th of a tank. thats when i checked the check engine light and found only code 21. i will say all the conectors from sitting exposed to the elements had some dirt and grime in them but they all made good connections would the dirt and grime be enough to not alllow a good ground on the tps. if so should i just try to clean the connector with some electrical cleaner and then check for the 5 volts. coming to it.
 
Bad connections can cause issues, yes.

Read the code 21 pages here http://api.viglink.com/api/click?format=go&key=29cc910212b73cceb3979c64a21a012b&loc=http%3A%2F%2Fcoloradok5.com%2Fforums%2Fshowthread.php%3Ft%3D240425&v=1&libid=1360610767044&out=http%3A%2F%2Fwww.gearhead-efi.com%2Fgearhead-efi%2Fdoc%2FTBIcodes.pdf&ref=http%3A%2F%2Fcoloradok5.com%2Fforums%2Fforumdisplay.php%3Ff%3D81&title=TBI%20Trouble%20codes%20-%20CK5%20Forums&txt=http%3A%2F%2Fwww.gearhead-efi.com%2Fgearhead...c%2FTBIcodes.pdf&jsonp=vglnk_jsonp_13606107767372

Never heard of the issue before just based on heads, but looks to me like engine vacuum can set this code, if you've got a vacuum leak, or "wrong" camshaft it could.

I'd follow the flowchart, you can't guess on these systems and do anything other than cost yourself a bunch of money in parts. Have to follow a logical path of diagnosis. Flow charts help.
 
i looked everywhere for a chart like that thanks for the chart. So looking at the circuit i should be able to grund the sensor direct to be able to tell if the ground is an issue also, is that correct. Parts cost isnt a problem because i work at a parts store so if i need to test the system by putting a part on it i just do it at work. I cleaned all the connections and the light is still on but i found something interesting when i unwrapped all the wire loom making sure all the connections are correct. i will take a picture of that later. This is a third vehicle so its not a daily driver and between work and school i only have a few days to work on vehicles a week.
 
Does your work have a scantool? Easiest way to do this. Flowchart will point you in right direction pretty quickly.

It would have to be way off, but any chance someone has monkeyed with the idle set screw? If the plug is missing off the housing, it's pretty likely. If it is, I'd also/maybe first do the "minimum air adjustment" which you can find via google. People seem to like to play with the idle screw when they have idle issues, and can't ever get it to idle right since you aren't supposed to mess with it. :)
 
We don't have an obd1 scan tool but i know if a shop that has one maybe I'll go down there but when i do the pin thing to the obd port it has 2 long flashes and one short flash.
 
So you get code 12 then 21? You will always get 3 code 12's first, it means the ECM is theoretically ok.
 
Is it with it to spend the money on a obd1 cable and software like the one from red devil river. All i have gotten when i do the paperclip trick is 2 long and one short maybe I'll have to try it again when i get home tonight. I didn't know i was supposed to get 3, 12s first.
 
Do you have a laptop? If you do, a $60 ALDL cable (or less, not sure what they cost today) and tunerpro RT (free) will do everything you need it to.

In your case, need to figure out your code situation first. If the CEL is on, then there must be a code, need to make sure that circuit is working right though.
 
so now i have a code 24 coming up now i believe it is becuase someone at some point spliced together the yellow and purple wirre... would that cause this. or is it because my speedometer cable has a kink in it and my speedo is not working.
 
when it goes into diagnostic mode you will get a code 12 3 times,then will throw out the problem codes,also three times each for each different code,when it is done it will do 3 more code 12's before it starts to repeat
 
Based on the code 24 (link I posted above) chart, it looks like it can/should set with an inoperative speedometer cable. Fix the cable, problem should disappear.
 
Okay that's what i was taking from it too but i have the neutral safety bypassed by splicing the yellow and purple wire together so i didn't know if that could cause it too
 
So the truck thinks it's in park/neutral all the time now then? That's not "proper" for ECM operation, and may cause problems as well. If I'm not mistaken there is some logic in the code for VSS/park neutral/IAC
 
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