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service engine light, 88 sububan.

ciffer

ciffer

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I have a service engine light light coming on in my "new" 1988 suburban, 114k miles. it was coming on then going off for the last 80 miles, now it is consistantly turning off about 1.5 miles after starting and is now staying on until i shut it off. It didn't do this last fall before i stored it in a field over the winter.I know it had a dead idle air controller, sometimes it stall on start up and needs to be pedeled, sometimes it revs to approx 2000-2500 on start up. this doesn't happen when the motor is warm.anyways, how do i pull the code?
 
Hit the link in my signature to the buyers guide, directions are at the bottom. :D
 
is there a way to check a code without shutting off the engine? the light is always off when i start it, have to drive a mile or two before it comes on.
 
Put a paperclip between A and B on the DLC. Turn key to acc mode (dont start engine). The first 3 codes will be 12 to let you know its in diagnostic mode. Will flash once pause and then flash twice (code 12) after 3 code 12 look at the next code that flashes that will be your trouble code. Very easy.
 
When the light comes on, the code that is set gets stored in the computer.

turn the truck off, connect the a-b pins, turn the key to the on position but do not start, the light should start flashing. 12 three times, then your code for whatever is faulting, then 12 three more times to finish the sequence.

a minute too late... :whistle: :D :doah:
2010-11-21191344.jpg
 
The engine reving higher on cold start is normal, its to warm the engine. Will come back down after a couple min. If you say the truck is new to you then sat a while do all the normal things like oil change, spark plugs new wires, cap, and check all emission hoses for cracks or breaks and that they are routed correctly. There should be a sticker above radiator that shows hose routing. You never know what previous owner did so just good to start with all the minor tune up type things.
 
i have had it for about 1 year, i stored it for about four months. changed the oil, replaced the alternator and put a good battery in last weeks. flashed "4" 6 times, with some longer pauses, probably "44" three times.
 
I believe code 44 is O2 sensor showing a lean mixture. Could be fuel filter, fuel pump headed down hill, or even the egr valve/vacuum leak.
 
a fuel filter wouldn't hurt, i think i have one sitting at home.

it has been turning on when i am on the highway under light throttle, although it doesn't seem to happen if i am just driving around town.

could it also need an o2 sensor?
 
Go ahead and change out 02 sensor and EGR valve. Cheap enough and easy to do. After that, disconnect batt. for a few minutes to clear codes. Drive around and see if light comes on again. And be sure to check all vacuum hoses and that there routed correctly.
 
Don't replace parts to diagnose a problem. You can test an egr valve for leakage without replacing it. You can test an O2 sensor too, but your code indicates its probably working.
 
TexasSilhouette said:
Don't replace parts to diagnose a problem. You can test an egr valve for leakage without replacing it. You can test an O2 sensor too, but your code indicates its probably working.
Click to expand...
I agree.

And the EGR valve is not cheap, at least not for my 91, it was close to $80. Diagnostic testing IS cheap AND easy, and will save a ton of cash and unneeded labor.
 
Normally I agree about not replacing parts to find a problem, but in this one case, I disagree.
If you have not changed the fuel filter in a while, go ahead.
I have seen lean fuel condition caused by that twice, and unless you did it last week, there is little downside to changing a fuel filter.
Especially with today's gas.

And it would tend to show up under light highway driving rather than in town.
 
I'll get tha put in and see what happens.I also remembered that I had an unusually thing happen twice, once last spring after normal driving and once last wednesday after a failed attempt to get the truck unstuck in mud.The motor would start be need to be pedaled considerably to keep running, otherwise it would cough, sputter and quickly stall. both times lasted a few minutes of low speed operation in a field (light throttle, under 10mph) Last year it coughed black smoke a few times, this time i pedalled it right away and didn't notice any smoke.possible connection?
 
Fordum said:
If you have not changed the fuel filter in a while, go ahead.
Click to expand...

Granted, my comment was more in refernce to EGR valves and O2 Sensors - non maintenance parts.

By the time you remove a fuel filter to check to see if it's obstructed (blow through it) you might as well put a new one on.

Replaceing the fuel filter is a good suggestion, a maintenance item that you need to know the age of.

My apologies for not having been clear.
 
My apologies for not having been clear.
Click to expand...

No, not at all. Actually I was not clear either.
When I said
but in this one case, I disagree.
Click to expand...
I actually meant to say I disagreed about one part, not the whole thread.

The only times I am a fan of replacing parts without determining whether or not they are bad, is when they are so old its pretty much a maintenance situation, there is no good way or its too costly to test them and replacement is easier or cheaper, or when its cheaper to just replace everything rather then trying to fix it.
And in some of those instances, its a temp swap.

For instance, if you suspect the computer, its easier to swap in a known good one from another car than run the large number of tests to verify that it is good.

And I have run into electronic circuits where I can shotgun the whole board and replace everything on it for $20 and 10 minutes of my time.

Considering what I was charging them per hour, and the fact that it might take 3 or 4 hours to test all the LSI chips, that was a bargain
 
for the cost of a few gaskets i could pull the EGR off the other Sub and try that.
 
The EGR is easy to test, don't bother swapping. However, I found that one one of my trucks it took nearly an hour to swap out due to the bolts being seized and of course it being in a totally hard to reach location.

Really, just test the EGR, that's an easy one.

And I agree with replacing maintenance parts, but not "hard" parts, if they need it. In fact, one of the first things I do when I buy a new truck is to change all those out under the assumption the previous owner never did. Then if something goes wrong, I know how long it's been since they were changed.
 
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