"Check Enging" light coming on... need suggestions

[Derf00]

\"Check Enging\" light coming on... need suggestions

Our '90 Jimmy, 350 TBI is developing an annoying problem. The Check Engine soon light comes on after driving at a sustained speed of 45-55. The light will stay on until the engine is shut off for any length of time and when restarted, the engine light will cycle normally and stay off. If you accelerate past 55 and cruise at any other speed it won't come on.

We have added an intake and cam and are running a Hyper-Tec chip.

Any ideas? Could this be caused by the chip?

Derf00
1990 K5 Jimmy 350 Edelbrock Performer TBI, 6in BDS Lift, Dana 60, 4.56, Corp 14B Detriot, 16x10 AE 589's, 37x12.5 SSR

 

[1990K5]

Re: \"Check Enging\" light coming on... need suggestions

take a paperclip and bridge the 1st and last port in the under dash diagnostic receiver, turn the key to acces. and your check light will spit out a code with an irratic series of flashes. this code can be deciphered by any haynes or chilton manuel, ive done it few times with my 1990 and it worked like a charm and pinpointed the issue every time. j.c.

 

[yeild2me]

Re:

hey derf, my 89 does the same thing...just started since it got pretty cold out....i have been meaning to pull the code, but dont think about it till it comes on the next time...

your right though, it is pretty annoying!!

350 TBI, 700R-4, NP241, D44-14FF, 4:10's, 38.5 TSL/SX's, full conv., full cage
<a target="_blank" href=http://www.yeild2me.rockcrawler.com>www.yeild2me.rockcrawler.com</a>

 

[CaptCrunch]

Re: \"Check Enging\" light coming on... need suggestions

Gotta find out why the light came on to figure out the problem. EGR and O2 codes are pretty common...

-Mikey
1987 Chevy K5 Blazer- 350 TBI
<a target="_blank" href=http://coloradok5.com/gallery/captcrunch>http://coloradok5.com/gallery/captcrunch</a>

 

[Derf00]

Re: \"Check Enging\" light coming on... need suggestions

Ok did what 1990K5 said to with the paperclip, and it only flashed once, what does that mean? Or did I do it right? I don't have a manual, any suggestions?

Derf00
1990 K5 Jimmy 350 Edelbrock Performer TBI, 6in BDS Lift, Dana 60, 4.56, Corp 14B Detriot, 16x10 AE 589's, 37x12.5 SSR

 

[HarryH3]

Re: \"Check Enging\" light coming on... need suggestions

It's pins A and B that need to be shorted together. They're right next to each other at the top right corner of the ALDL connector. Then you switch the key to the "run" position and watch for the flashes from the Check Engine light. If you have an AutoZone nearby, they'll give you a little 2-pronged key that does the shorting, along with a brochure that tells you how to use it and what the codes mean.

<font color=black>HarryH3 - '75 K5</font color=black>
<a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
It's a great day to be alive...

 

[Derf00]

Re: \"Check Enging\" light coming on... need suggestions

Harry,

Did it your way with the same results.

Derf00
1990 K5 Jimmy 350 Edelbrock Performer TBI, 6in BDS Lift, Dana 60, 4.56, Corp 14B Detriot, 16x10 AE 589's, 37x12.5 SSR

 

[HarryH3]

Re: \"Check Enging\" light coming on... need suggestions

Then something isn't right.

Even if there are no codes stored, it should always flash a code 12 (flash, pause, flash flash) just to indicate that the computer is working. If pins A&amp;B are shorted together and it doesn't flash at least a code 12, then the first step is to make sure that the chip is installed correctly. If it looks OK, then try installing the stock chip just to run the test again. If it flashes the light but the new chip won't, then you have a bad chip.

<font color=black>HarryH3 - '75 K5</font color=black>
<a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
It's a great day to be alive...

 

[BurbinOR]

Re: \"Check Enging\" light coming on... need suggestions

Fred, it's worth buying a scanner for not only this diagnosis but for future monitoring, etc. You can pick up an Auto Xray (PN10110) at a Schucks/Kragen/Checker for about $150.

From your description, sounds like EGR but that is hard to tell from here

. Get a scanner, pull the code, and you'll know in a heartbeat.

How long has the intake/cam/chip been in the truck?

<font color=blue>'79 ONE TON TPI K5 - See it at---&gt;<a target="_blank" href=http://www.blazzinor.rockcrawler.com>www.blazzinor.rockcrawler.com</a>

 

[HarryH3]

Re: \"Check Enging\" light coming on... need suggestions

I'm not sure that the scanner will even show anything in this instance. The ECM isn't responding to shorting pins A &amp; B together, so it may not send any data to the serial port either.

<font color=black>HarryH3 - '75 K5</font color=black>
<a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
It's a great day to be alive...

 

[BurbinOR]

Re: \"Check Enging\" light coming on... need suggestions

True, but as you know, a scanner is useful for many uses in the future, and I feel anyone with FI computers should have more than a paper clip as a diagnostic tool

........lol.

<font color=blue>'79 ONE TON TPI K5 - See it at---&gt;<a target="_blank" href=http://www.blazzinor.rockcrawler.com>www.blazzinor.rockcrawler.com</a>

 

[HarryH3]

Re: \"Check Enging\" light coming on... need suggestions

I totally agree with that!

<font color=black>HarryH3 - '75 K5</font color=black>
<a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
It's a great day to be alive...

 

[kpanza]

Re: \"Check Enging\" light coming on... need suggestions

Just to add to what Harry said, you will get three consecutive Code 12s when it starts. (Flash, pause, flash-flash - 3 times in a row) After the three "12s" will be the error codes (if any), all of which will also be flashed three times consecutively. If there are no error codes, it will just keep flashing code "12s" at you...

And I agree with Harry, if you are actually shorting the A and B terminals together and not getting anything, you could have a problem with that chip or with the ALDL itself...

 

[Derf00]

Re:

Harry,

You were right on. When the AB terminals which are on the right side of the plug(my shorter dosen't know his rt from his left when he is under the dash) are shorted together we got a Code 12 and then Code 32, which is the ERG valve.



Derf00
1990 K5 Jimmy 350 Edelbrock Performer TBI, 6in BDS Lift, Dana 60, 4.56, Corp 14B Detriot, 16x10 AE 589's, 37x12.5 SSR

 

[HarryH3]

Re:

I just about spewed my drink when I read that!

That's too funny!

Indeed it does help to short the correct 2 pins together!

Before you replace the valve, make sure that the vacuum line to it, and to the solenoid that controls it are connected correctly. The solenoid should have 12 volts going to one side of the connection. The ECM grounds the other side to turn it on and send vacuum to the EGR valve.

<font color=black>HarryH3 - '75 K5</font color=black>
<a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
It's a great day to be alive...

 

[CaptCrunch]

Re:

You can also pull off the egr and make sure it isn't all gucked up. Sometimes the grime causes them to stick

-Mikey
1987 Chevy K5 Blazer- 350 TBI
<a target="_blank" href=http://coloradok5.com/gallery/captcrunch>http://coloradok5.com/gallery/captcrunch</a>

 

[dyeager535]

Re:

Had a friend selling a truck that had an EGR problem, pulled it out, cleaned up the valve and the EGR "port" in the head, and it ran like a champ. Still held vacuum, it was basically all the carbon built up all over the thing that needed to be removed, apparently it was just bound up.

Dorian
My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
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