LT1-LT4 Modifications 1993-97 Gen II Small Block V8

LT1 diagnostic help

Thread Tools
 
Search this Thread
 
Old Apr 21, 2009 | 12:47 PM
  #1  
Bonestock!'s Avatar
Thread Starter
Teching In
 
Joined: Jan 2009
Posts: 48
Likes: 0
From: Panama City, FL
Default LT1 diagnostic help

I have a 128k '94 Camaro Z28 A4 here that belongs to one of my wifes co-workers. Its has PS headers, decat, borla CB and I "think" a very mild cam. He bought the car this way so info is very hard to come by.

Symptoms:
Runs very rich (heavy black smoke on hard accel)
Pops & backfires through the exhaust when you get on it
NO POWER, it will not even spin the tires.

The owner claims to have replaced the Opti, wires and plugs within the last 8 mo. EDIT: The o2's as well.

I hooked up a scan tool, Modus and paper clip all to the ALDL and can not check for codes. The engine will go into field service mode (fan on & CEL flashing) but will not flash any codes. I just get a rapid CEL flash. The Modus can not communicate with the ECM or the ABS module. I checked all the fuses and none appear to be blown.

Ideas? I am trying to help this kid out so any help would be great.
Reply
Old Apr 21, 2009 | 12:51 PM
  #2  
ss.slp.ls1's Avatar
TECH Senior Member
15 Year Member
iTrader: (36)
 
Joined: Jan 2008
Posts: 8,184
Likes: 28
From: Orange County, CA
Default

Originally Posted by Bonestock!
I have a 128k '94 Camaro Z28 A4 here that belongs to one of my wifes co-workers. Its has PS headers, decat, borla CB and I "think" a very mild cam. He bought the car this way so info is very hard to come by.

Symptoms:
Runs very rich (heavy black smoke on hard accel)
Pops & backfires through the exhaust when you get on it
NO POWER, it will not even spin the tires.

The owner claims to have replaced the Opti, wires and plugs within the last 8 mo. EDIT: The o2's as well.

I hooked up a scan tool, Modus and paper clip all to the ALDL and can not check for codes. The engine will go into field service mode (fan on & CEL flashing) but will not flash any codes. I just get a rapid CEL flash. The Modus can not communicate with the ECM or the ABS module. I checked all the fuses and none appear to be blown.

Ideas? I am trying to help this kid out so any help would be great.
Are you trying to read codes using a 12-pin OBD1 scanner?
Usually a flashing SES signifies a misfire detected, but I didn't know if the '94's had misfire detection or not. That could explain all of the symptoms above. You need to find out what the code(s) are.
Reply
Old Apr 21, 2009 | 12:56 PM
  #3  
Bonestock!'s Avatar
Thread Starter
Teching In
 
Joined: Jan 2009
Posts: 48
Likes: 0
From: Panama City, FL
Default

I cant get into the ECU to read the codes. Like I stated I have tried everything from a paper clip to a $13k Snap on Modus. The ECU and even the ABS system arent communicating via the diagnostic port (aka ALDL).
Reply
Old Apr 21, 2009 | 12:59 PM
  #4  
ss.slp.ls1's Avatar
TECH Senior Member
15 Year Member
iTrader: (36)
 
Joined: Jan 2008
Posts: 8,184
Likes: 28
From: Orange County, CA
Default

Originally Posted by Bonestock!
I cant get into the ECU to read the codes. Like I stated I have tried everything from a paper clip to a $13k Snap on Modus. The ECU and even the ABS system arent communicating via the diagnostic port (aka ALDL).
Does the car have the 12 pin or 16 pin ALDL?
Reply
Old Apr 21, 2009 | 01:03 PM
  #5  
Bonestock!'s Avatar
Thread Starter
Teching In
 
Joined: Jan 2009
Posts: 48
Likes: 0
From: Panama City, FL
Default

12pin OBD1 port.
Reply
Old Apr 21, 2009 | 02:16 PM
  #6  
djjab57's Avatar
TECH Addict
15 Year Member
iTrader: (17)
 
Joined: Jul 2007
Posts: 2,496
Likes: 0
From: Texas
Default

my light didnt flash when my plug wire was burnt up. its an early 94 Z28 OBD 1
Reply
Old Apr 22, 2009 | 12:12 PM
  #7  
Bonestock!'s Avatar
Thread Starter
Teching In
 
Joined: Jan 2009
Posts: 48
Likes: 0
From: Panama City, FL
Default

Anyone have an idea why the ECU & ABS isnt communicating via the diagnostic port?
Reply
Old Apr 22, 2009 | 12:18 PM
  #8  
ss.slp.ls1's Avatar
TECH Senior Member
15 Year Member
iTrader: (36)
 
Joined: Jan 2008
Posts: 8,184
Likes: 28
From: Orange County, CA
Default

I have read that the port is on the same circuit as the cigarette lighter. See if the lighter is working, if not, you might have a blown fuse in your interior fuse block.
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-1

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-2

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-3

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-4

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-5

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-6

10 Camaros You Should Never Buy

 
story-7

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo
story-8

Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0

 Brett Foote
story-9

10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever

 Verdad Gallardo
Old Apr 22, 2009 | 01:11 PM
  #9  
Bonestock!'s Avatar
Thread Starter
Teching In
 
Joined: Jan 2009
Posts: 48
Likes: 0
From: Panama City, FL
Default

Just checked it, its good.

*stumped*
Reply
Old Apr 22, 2009 | 01:48 PM
  #10  
djjab57's Avatar
TECH Addict
15 Year Member
iTrader: (17)
 
Joined: Jul 2007
Posts: 2,496
Likes: 0
From: Texas
Default

I bought one of these seems to work ok http://cgi.ebay.com/ebaymotors/Autox...1%7C240%3A1318
Reply
Old Apr 22, 2009 | 04:15 PM
  #11  
Bonestock!'s Avatar
Thread Starter
Teching In
 
Joined: Jan 2009
Posts: 48
Likes: 0
From: Panama City, FL
Default

Originally Posted by djjab57
I bought one of these seems to work ok http://cgi.ebay.com/ebaymotors/Autox...1%7C240%3A1318
I tried the simple scanners and the expensive professional stuff. Still can read from the ALDL.
Reply
Old Apr 22, 2009 | 11:44 PM
  #12  
Isphius's Avatar
Teching In
 
Joined: Jun 2008
Posts: 10
Likes: 0
Default

94 cars with the obd1 style plug you cant flash codes out with a paper clip in the A&B and i have yet to find an adapter for my obd2 scanner. I could also use some help on this. Is there a way to adapt the obd2 plug to the ALDL using jumper wires?
Reply




All times are GMT -5. The time now is 08:05 AM.

story-0
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-1
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-2
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-3
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-4
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-5
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-6
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-7
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE
story-8
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0

The world was a better place when it was still around.

By Brett Foote | 2026-01-23 09:20:37


VIEW MORE
story-9
10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever

Slideshow: The 7.0-liter LS7 was designed for absolute cutting-edge performance.

By Verdad Gallardo | 2026-01-07 18:36:00


VIEW MORE