Isolating the Computer, ESC, and Distrib Module (continued)

Tonight I pulled out the computer, and it didn't have any chip in it. I had figured the prior owner would have had a reason to pull the chip and leave it in a bag on the flor (performance chip or somehting), but nope, just an empty socket. God knows why the prior owner would have pulled the chip.

I installed the chip, and I no longer need:

1) the hot to the ornge wire (fuel pump power) 2) The OBD1 debug jumper (A&B). 3) The hose-clamp that increased the idle a little.

With the jumper and engine not running, the computer flashes codes (12,23,34,41,42). For NG cretique and ideas, my interpretation of these by reading Haynes is:

12 - since it goes onto other codes, this just starts the sequence of reading codes. {True?} 23 - MAT low temp indication (where it this one?) 34 - Vacuum sensor or MAP sensor (are these the same or is there a seperate vac sensor - I probably do have vacuum issues) 41 - {not in my book, anybody know what it is?} 42 - EST (Electronic Sparc Timing) - "Electronic spark timing bypass circuit or EST circuit is grounded or open. A malfunction ing HEI module can cause this code" (? is this pointing at the distributor-module?) {The last I checked timing it was about 8 degrees BTC - before I tightened the bolt - guessing it's between 5 & 20 degrees now - will go check as I post}.

And yea I'm still trying to figure out what to do with this truck (keep/sell/junk). Of coarse it's getting closer to something i could sell with a clear concience. And yea the prior owner was dishonest - I wouldn't sell something like what I bought. I guess I bought this from the kind of owner that you guys often imagine me to be - cludge artist, etc - but at least I'm honest about my cludges and wouldn't try to hide them from a buyer.

Ideas and suggestions are appreciated - though please be patient as I do tend to jumper and cludge my own test cases.

Thanks, Elliott

Subject: Isolating the Computer, ESC, and Distrib Module > Date: Wed, 31 Mar 2004 19:09:12 -0500 > From: snipped-for-privacy@comcast.net > Newsgroups: alt.trucks.chevy, alt.autos.4x4.chevy-trucks > > Anybody know how to isolate the Computer, Electronic Spark > control, and the Distributor module? The parts-throwing > approach would be $50 for the ESC, $75 for the computer, > and whatever Autozoo price for the module. Would like to > be able to locate test-points for a VOM with known expected > voltages to test for. It could also have something to > do with the ignition switch and fuel-pump relay/gnd. I'm > running out of time for the project and could really use > the vehicle if it were working. This is on the 87 S-10 with > a 2.8L V6 TBI. It ran for a few minutes with the motor dropped > in before the fuel pump pumped all night (probably had a bad FP-relay > that I have replaced). I think I have all of the wiring hooked up > but there are a couple wires that look like they haven't been hooked > up for years. > Thanks in advance, > Elliott
Reply to
Elliott
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Reply to
Elliott

Try this page:

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Click on each of the codes to gain more info on them. This page is good. Read all of it, then go on to the codes. The page is designed around the Sy/Ty family of S10's (4.3), so some info may or may not apply to your engine

Low readings on these circuits (coolant and MAT) are often caused by corrosion at the connector.

Reply to
John Alt

Reply to
Elliott

A diagnostic circuit check should have revealed at least a code 51 (prom error) and lead you directly to the problem.

IIRC, this is an 87 S-10 with a TBI 2.8 liter V-6 my answers will be addressed towards this as being the model, year and engine...

Not true. Code 12 means that the ECM is not receiving distributor reference pulses from the ignition module. Since the engine is not running, this is a normal condition. Since code 12 is the lowest numerically possible, it shows up first. In a rather crude way, it does show a minimal ability that the computers diagnostic routines are somewhat functional.

The 2.8 didn't use a MAT sensor. The 4 cylinder 2.5 did. Possible causes are; wrong computer, wrong PROM, defective computer, defective PROM. Can't see this occurring any other way.

Yours has only a MAP sensor. make certain that it's plugged in and that the vacuum line is connected to a manifold vacuum source and that vacuum source is not plugged with gunk.

Code 41 is not valid for this application. Code 41 is a valid code in certain other GM applications but they wouldn't apply to this particular vehicle due to components it never came with (i.e., a cam position sensor).

Code 42 is the normal trouble code that would set if the set timing connector was opened as in when the base ignition timing was being set. Check the set timing connector first.

The ECM doesn't know where the timing is set.

Reply to
Neil Nelson

Reply to
Elliott

Ok I just tried again...

disconnected the battery, jumpered pins B&C of the MAP sensor, reconnected battery, started for 10 seconds (got a light in 5), shut off, jumpered, and read out codes 12 & 23.

  1. a non existant MAT per Neil's earlier response - hmmm.

Restarted and ran for about 30 seconds, shut off, jumpered, and read 12, 23, 34, 41, and 42.

  1. a jumped-out MAP still generates a code - hmmmm.
  2. another non existant (cam posn) per Neil's post - hmmmm.
  3. EST - (or timing connector per Neil's comment). Where is the timing connector? My timing reads 16 degrees with a light but I don't know how to bypass via a connector. My impression is that I should jumper something in a connector, and set the timing to about 8 degrees (true? accurate? - no stickers to provide data and haynes references stickers). Will need to let it cool before adjusting the timing since I tightened down the distributor bolt yesterday.

Ideas? Computer fried? Wrong computer?

Thanks, Elliott

Elliott wrote:

Reply to
Elliott

See, this is where we get into trouble with you. You know for a fact you either have the wrong PROM or a bad computer, yet you continue to troubleshoot crap. The codes are meaningless until we know the computer has the sensors it expects on the terminals. On the computer is a 7 digit number. IIRC, for your truck, it is supposed to be 1227747. I posted days ago (March 31) and asked you what it was. Give us that number. There are other numbers that work correctly in that application. Stop now before you fry something. Not all the terminals have current protection on them. Some like the EGR and TCC terminals can push amps and can fry something if it's the wrong computer. The pinouts were different on some car computers. If the computer number is good, you can get by with a PROM. So close the hood and wait till you've got the right computer.

Reply to
John Alt

"John Alt" wrote

I was thinking...."just close the hood".

Ian

Reply to
shiden_Kai

I'd call a wrecking yard and see what they have in the way of a tow truck. B

Reply to
Battleax

'When you want to get out of a hole, step one is to stop digging' seems appropriate here...............

Reply to
TranSurgeon

Reply to
Elliott

What I "think" it should be. I don't own a 2.8, never have, and undoubtedly never will. I've dealt with them enough to know they are evil. But, in that model year, that is about the only number that was used on trucks and vans. There are several others that will work.

Reply to
John Alt

Reply to
Elliott

Hold your horses. I said I wasn't sure. Turns out your looking for a

1227429

At least according to these guys. Someone with a better reference source might want to double check this

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Get the right computer and PROM. It has to be for a 2.8 automatic

Reply to
John Alt

BTW, your computer was for a 3.8 V6.

Reply to
John Alt

Reply to
Elliott

Reply to
Elliott

Jesus, Mary and Joseph..........just go down to AutoZone and get the CORRECT one, put the one that's in your truck in the box and turn it in for core charge.....

The AutoZone sales drones don't KNOW or CARE that it's not 'the same kind' that they sold you

WHY do you INSIST on making EVERY DAMNED THING so much harder than it really is ?????

Reply to
TranSurgeon

If your referring to the chip you found laying on the floor, what do you think I'm going to tell you to do with it?

The new (used) computer should have the stuff inside it. Just make sure it's from a 2.8 auto circa 86 to 88. If it's not, they should be able to look it up.

Reply to
John Alt

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