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Username Post: 92 1500,350, runs perfect with check engine light        (Topic#365821)
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
07-16-21 03:03 PM - Post#2823330    

Hello everyone,
I hope you could give advice to help confirm what I may already know
1992 350, auto, 216k
Known mods: GE perforemnce intake manifold
Issue: truck runs perfect when check engine light is on. Stutters and runs ruff when check engine is off.

Codes: unable to read, constant steady light, even bought that 30 dollar GM code reader thing to eliminate my dumbass and can’t get anything. I was able to get it flash 12 once yesterday with the truck running and A&B jump it flashed code 12 and then ???????????

Professional shop: bought it and barley ran, shop retimed
It and said was off 20 degree’s. Guy said it was a very strong truck. Also said he was surprised how well it ran/strong it was. As he says normally their shot boxes now. Light was on, ran good, light started stuttering and then ran like crap?

So called history of the truck: guy passed due to covid and wife said it was his baby. Not to long ago (few years) had an intake and heads redone? (Can kind of confirm due to GM performance intake manifold.

So far, I’ve cleaned all the sensors, just finished checking EGR valve to make sure operation(ran all the way up to 2k when it was off,lol) (currently waiting to put back on as truck is hot,lol.) Also did cap, rotor, wires and plugsSo far

When truck is cold (mornings only) I can see in the TBI and i can see fuel increase but seems the truck hesitates for a sec and then goes. When driving with check engine light off. Truck warm or cold it kind of can see the rpms jump a little, truck still goes, just not as smooth. I did check the ECM (yesterday) and seems like a refurb(says RN on the prom chip holder) but the ECU was hot like I could fry an egg on it. Just touched the ECM now and seems normal (I can actually handle it). I’ve blown out all lines just to check and see no visual leaks. I’m 99.9% sure the ecm or prom is bad.

I know this isn’t a lot to go by as I just got the truck 2 weeks ago and kind of using it like a farm truck around the property until I can hash this out. Anyone know of any companies that can check ECM/Prom? Is their ant sites to use to
Cross reference to make sure the right ECM or prom is correct t? Or any suggestions are greatly appreciated!

Thank you in advance, like I said I know it’s not a lot to go on. I also know I should check the fuel pump but I just don’t think it’s that yet.



Edited by 1992chevy1500 on 07-16-21 03:04 PM. Reason for edit: No reason given.

 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
07-17-21 05:28 PM - Post#2823387    
    In response to 1992chevy1500

So I reread my post and seemed kind of crazy. Sorry I was a little post to say the least. Here some video to see. Now the SES is flashing like its a misfire. Still can’t read any codes though. Gonna see if I can grab a fuel filter tomorrow. Maybe that can help.

Video 1
https://youtube.com/shorts/Azcvlu46qPk?fe ature=sha...
Video 2
https://youtube.com/shorts/uCmB300KD1E?fe ature=sha...



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
07-17-21 06:08 PM - Post#2823391    
    In response to 1992chevy1500

Codes are read with the key on engine off.

It should flash code 12 three times and then the problem trouble codes can flash out if there are any stored.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
07-17-21 07:20 PM - Post#2823397    
    In response to Chevytech

I am really glad you commented, actually the whole reason I joined this forum was seeing your advice given to multiple people. Sadly, trying to read the codes won’t happen. I even bought that 30 dollar plug thing from autozone where you can switch from check engine to abs light check. Dosent matter does nothing and I bought that just to see maybe I was doing it wrong. At this point, I’m checking all the grounds and Probly leaning towards a ecm/pcm replacement. I tried to get a fuel pressure tester but everywhere I go, seems like they are all rented out.



 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
07-17-21 07:30 PM - Post#2823400    
    In response to Chevytech

My current situation

https://youtu.be/ctFfKavGylc



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
07-18-21 05:54 AM - Post#2823417    
    In response to 1992chevy1500

If jumping the test terminal, to the ground terminal, of the ALDL affected the Check Engine Light operation with it running, then the ALDL wiring must be good.

It sure sounds like the ECM has failed and it is running in the backup mode off the PROM.

My guess is it has a 1227747 ECM. If so I would check these power feeds and grounds at the ECM:
Key on test for 12 volts at B1, A6, C16
Grounds to test – D1, D2, D6, A11, A12

If voltage readings check out good, then I would be trying another ECM.

Remember to swap the chip out of the old ECM into the new ECM unless you get a used unit with the exact same chip number.

  • Quote:
I am really glad you commented, actually the whole reason I joined this forum was seeing your advice given to multiple people.

Thank you!

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


Edited by Chevytech on 07-18-21 11:55 AM. Reason for edit: Fix more wording errors

 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
07-18-21 12:04 PM - Post#2823438    
    In response to Chevytech

First thank you very much! Sadly it is raining. So I did a VIN part lookup on AcDelco and this is the ECM it said it was

Engine Control Module/ECU/ECM/PCM
Part Number: 88999164

I see if I can cross-reference it and see what I get. Sadly it’s pouring buckets outside so my honey todo list is inside today. I will test soon as the rain stops or tomorrow and let ya know what I find! I really do appreciate a direction on all of this!

Also dumb question. Should I back probe with the ecm plug in or can I get away with disconnecting it and testing on the plug in-side?




Edited by 1992chevy1500 on 07-18-21 12:11 PM. Reason for edit: No reason given.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
07-18-21 12:25 PM - Post#2823440    
    In response to 1992chevy1500

  • 1992chevy1500 Said:
First thank you very much!

You're welcome.

  • 1992chevy1500 Said:
Should I back probe with the ecm plug in or can I get away with disconnecting it and testing on the plug in-side?



On this it would be OK to unplug it and test on the plug in-side.

I will look and see what I can find on that part number with a search.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
07-18-21 12:30 PM - Post#2823442    
    In response to Chevytech

Thank you.

Was able to run out and check connectors, both connectors are blue and seems A1 is green and white and B1 is orange



Edited by 1992chevy1500 on 07-18-21 12:40 PM. Reason for edit: No reason given.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
07-18-21 12:46 PM - Post#2823445    
    In response to 1992chevy1500

  • 1992chevy1500 Said:

...Part Number: 88999164...




That looks to be a PCM for a vehicle with a powertrain control module to shift the transmission.
In 1992 the 4L80 in the 2500 trucks used a PCM, but I have never seen a 1992 1500 that uses a PCM.

Get the number off you old computer and let me know what you have.

We need to find out what it has for a computer before testing.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
07-18-21 12:53 PM - Post#2823446    
    In response to 1992chevy1500

  • 1992chevy1500 Said:
A1 is green and white and B1 is orange



That matches with what I show for a 1227747 ECM.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
07-18-21 01:11 PM - Post#2823447    
    In response to 1992chevy1500

Another search I did shows the 88999164 is for California emissions system.

If the truck has California emissions it will show that on the emissions label under the hood.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
07-18-21 02:18 PM - Post#2823450    
    In response to Chevytech

  • Chevytech Said:
  • 1992chevy1500 Said:
A1 is green and white and B1 is orange



That matches with what I show for a 1227747 ECM.



Ok, it was bought and driven off in Tennessee. No emissions. I will check tomorrow as rain hasn’t lifted and report tomorrow. Thank you for ur help on this.



 
stumppuller 
"10th Year" Gold Supporting Member
Posts: 934
stumppuller
Loc: Canada
Reg: 11-01-04
07-18-21 08:00 PM - Post#2823471    
    In response to 1992chevy1500

  • 1992chevy1500 Said:


Was able to run out and check connectors, both connectors are blue



If they look like those pictured, then they are considered black connectors.

Attachment: index.jpg (5.54 KB) 3 View(s)




-91 Sierra C2500, now K2500
-81 Chev K20


 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
07-19-21 11:50 AM - Post#2823506    
    In response to stumppuller

Thank you for the clarification! Makes sense,lol sorry I did a quick look while dodging shower 2021 of this summer. 90 days of rain.. one day of sunshine,lol



 
G. Baker 
Poster
Posts: 54

Loc: Ontario Canada
Reg: 12-18-15
07-28-21 05:28 PM - Post#2824062    
    In response to 1992chevy1500

Two thoughts. Disconnect battery for 10 minutes, Key OFF. Just a chance....
Cut small piece of black tape and place over Engine money light.
Drive it.
Wishing I could figure out why my Caddy XLR trunk opens at random times ....
G. Baker



 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
08-10-21 04:15 PM - Post#2824897    
    In response to G. Baker

Hey all, sorry I had a personal family matter that took me sometime to deal with so I have made some progress or Atleast I believe so. So I was finally able to test all the connections
B1-12.34
A6- 12.35
C16-12.28

D1-good
D2-good
D6-good
A11-good
A12-good

Then I dug into the ECM and notice that the PROM had the same Z or N black marker as the ECM (ECM) seems to be a reman one.
PROM CHIP- DELCO AWLB 7706
I sprayed some electric parts cleaner into the prom and plug because what else do I have to lose?!?
Video of ECM: https://youtube.com/shorts/q9nivNFkdPo?fe ature=sha...

Then for poopsand giggles I plugged in my cheap OBD1 reader (again bought it to cancel our user error) and it finally gave me a code!!!! I got the 12 x3 and then 51 which I saw is PROM error. Now this code with the reader will display with the truck on or off.
Video here: https://youtu.be/VsOjrX0L0_0

Now I took the OBD1 reader off and the check engine spazzed like it was having a spaz attack
Video here: https://youtube.com/shorts/Sh5BudoYf-E?fe ature=sha...

So now I’m wondering if the PROM is the issue now. It might of been bought with the ECM and never replaced with the correct one?? So now I have 2 questions, can we confirm the correct ECM and now right PROM?
My VIN is 1GCDC14K8NZ119072

Thank you as always.




 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
08-10-21 05:31 PM - Post#2824905    
    In response to Chevytech

So late evening update, I think I fixed her?
Bad- with check reader attached the light will blink on and off like a miss fire and in the key on position will flash code 51.
Good- with the code reader off and just starts as normal. Rpms on start even register over 1k like a regular car starting. Runs and drives.. no hesitations, no jerking.. think maybe their was some corrosion on the prom which was causing issues

Only baby issue right now is at idle it seems like it’s gonna die for a split second but catches itself… i am gonna test drive it all this week and let ya know if anything comes back. But she revs amazing.. when she warms up.. runs like a champ!!!

Fingers crossed



 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
08-11-21 04:43 AM - Post#2824921    
    In response to 1992chevy1500

Morning update
So started it up this morning and she ran great. Rpms went up and held like it was warming up and idle smoothly. Plugged the reader in and still get code 51. Turned it off and started it again and ruff idle when it warms up. Never dies just seems like it is but catches itself. I’m gonna order new ECM and PROM set and see if that fixes the issue but I can now drive the truck with no issues.

P.s- I was able to find the exact chip that looks like mine in the ECM same markings and cover as well

https://www.ebay.com/itm/223543447327?_trk parms=ai...



Edited by 1992chevy1500 on 08-11-21 09:39 AM. Reason for edit: Edited due to finding prom chip

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
08-11-21 01:49 PM - Post#2824948    
    In response to 1992chevy1500

It set a code 51, replace the PROM.

I looked up that prom code AWLB and it looks correct for your truck.

BBC AWLB
Year 1992
Eprom 16157705
ECM 16146299
ID 7706
ID 5841
platform C1
Engine LO5
Engine 5.7
Trans MD8
Trans Auto

Sorry for my slow reply. I have been very busy!

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
08-11-21 05:32 PM - Post#2824958    
    In response to Chevytech

Chevy,
Thank you man! Also don’t worry about it! It’s been crazy here too. Only took me three months to get back to the truck due to personal poopoo myself! You are awesome and I just have one last question. Does the 4 digit number have to be the same? I currently states 7706. But I see others.. or does the Letters only matter?

Found last one on a eBay website. Looks exactly like mine in the truck (same holder and everything) matched all the numbers so I bought it. I’ll let ya know what happens when I install it.



Edited by 1992chevy1500 on 08-12-21 05:29 AM. Reason for edit: Bought part

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
08-12-21 01:19 PM - Post#2825019    
    In response to 1992chevy1500

  • 1992chevy1500 Said:
Chevy,
Thank you man! Also don’t worry about it! It’s been crazy here too. Only took me three months to get back to the truck due to personal poopoo myself! You are awesome and I just have one last question. Does the 4 digit number have to be the same? I currently states 7706. But I see others.. or does the Letters only matter?

Found last one on a eBay website. Looks exactly like mine in the truck (same holder and everything) matched all the numbers so I bought it. I’ll let ya know what happens when I install it.


You're welcome!

The letters give you the application.

I just don't know what the different PROM ID numbers indicate.

For all I know it could be a different manufacturing plant, or lot.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
08-12-21 01:33 PM - Post#2825021    
    In response to Chevytech

Well thank you again! After I cleaned the Prom slot with EBC electronics cleaner, everyday the truck runs better and stronger! I really couldn’t of done it without your support and guidance on this! The prom should be here Wednesday-Thursday so we will see. Ether way next week I get it registered and make all the trips to the dump and home depo I’ve been dreaming of!,lol



 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
08-20-21 12:07 PM - Post#2825606    
    In response to Chevytech

So ordered a new prom and just came in the mail. 100% disco battery and everything and put everything up. Still got the same code 51. Currently waiting for truck to cool down to replace CTS. I will provide an update once changed and I get a chance to look at everything again.



 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
08-20-21 03:00 PM - Post#2825614    
    In response to 1992chevy1500

Update
So replaced Prom, when I did the SES light just flickers. I can plug the leads and still read codes on and off? Still says 51- Prom. Also now I got a wired fast idle (1500) I replaced the CTS because I was pulling that when I started the truck so I could drive it because the idle would actually be too low. Seems that is now just a thing of staying fast idle. At this time, the truck can run and drive just the flicker SES and high idle. I sprayed break cleaner around everything didn’t effect anything. So as of right now.. I think I’m just gonna drive it ??????? If anything should change or if I figure out the answer I will sure to post it. I’m gonna censored around with the Sensors on the TBI next and see if that does anything



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
08-20-21 03:04 PM - Post#2825615    
    In response to 1992chevy1500

If replacing the PROM did not fix the code 51 and you are sure you had all pins in the socket, and it was fully seated, then the next step is to replace the ECM.

Sorry I don't have better news.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
1992chevy1500 
Newbie
Posts: 16

Reg: 07-16-21
08-20-21 04:27 PM - Post#2825622    
    In response to Chevytech

Chevy, hey! You got me this far. I’ll try to replace the ECM when I can find a deal on one. It is what it is! It’s a 29 year old truck and god knows how many hands have been in it. It Atleast runs and drives now! Before it would jerk, pop, backfire. And do everything in between. I really do appreciate it! I’ll figure it out or drive it until it explodes . I bought with the soul purpose of doing home depo and dump runs.. it will fit it’s purpose to a T. Thank you again man! I really do appreciate it

P.a- now it’s a solid SES and I can’t read codes



Edited by 1992chevy1500 on 08-20-21 05:25 PM. Reason for edit: No reason given.

 
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