Diagnostic mode (shorted ALDL) doesn't work
#1
Supreme Member
![](https://www.thirdgen.org/forums/images/ranks/tgo10.gif)
Thread Starter
iTrader: (2)
Join Date: Jul 2001
Location: Western PA
Posts: 1,000
Likes: 0
Received 1 Like
on
1 Post
Car: 1986 IROC-Z
Diagnostic mode (shorted ALDL) doesn't work
For some reason, I can't seem to get into the "diagnostic" mode of the car by shorting out pin A and pin B on the ALDL connector. I short the pins, turn ignition to ON, and nothing happens (no flashing SES light, fans stay off). Interestingly enough, my fan runs constantly ONLY when the engine is running. If the key is ON, but the engine is off, the fan doesn't turn on. The SES light is not lit when driving. Over the last few months I did some work to the car, including removing the A/C and "redoing" a few wire harnesses. It's possible that I messed up a connector, but I really don't think that I did that. What could cure these symptoms?
#2
Supreme Member
![](https://www.thirdgen.org/forums/images/ranks/tgo10.gif)
uM Have you ever actually SEEN your check engine light, come on? its possible you just have a burnt out bulb or the bulb is missing...
when you start the car it should come on for a few seconds. if it doesnt then the bulb is prolly bad or gone... or theres black electrical tape over it (happened to me)
when you start the car it should come on for a few seconds. if it doesnt then the bulb is prolly bad or gone... or theres black electrical tape over it (happened to me)
#3
Supreme Member
![](https://www.thirdgen.org/forums/images/ranks/tgo10.gif)
Thread Starter
iTrader: (2)
Join Date: Jul 2001
Location: Western PA
Posts: 1,000
Likes: 0
Received 1 Like
on
1 Post
Car: 1986 IROC-Z
Originally posted by Kingtal0n
uM Have you ever actually SEEN your check engine light, come on? its possible you just have a burnt out bulb or the bulb is missing...
when you start the car it should come on for a few seconds. if it doesnt then the bulb is prolly bad or gone... or theres black electrical tape over it (happened to me)
uM Have you ever actually SEEN your check engine light, come on? its possible you just have a burnt out bulb or the bulb is missing...
when you start the car it should come on for a few seconds. if it doesnt then the bulb is prolly bad or gone... or theres black electrical tape over it (happened to me)
#4
Supreme Member
![](https://www.thirdgen.org/forums/images/ranks/tgo10.gif)
Thread Starter
iTrader: (2)
Join Date: Jul 2001
Location: Western PA
Posts: 1,000
Likes: 0
Received 1 Like
on
1 Post
Car: 1986 IROC-Z
Boy, do I feel stupid
. Turns out that I shorted out the two LEFTmost pins in the top row, not the two rightmost pins. I guess I read the ALDL diagram backwards... or I'm just a forgetful moron who hasn't driven his car since September. It works now
.
![Roll Eyes (Sarcastic)](https://www.thirdgen.org/forums/images/smilies/rolleyes.gif)
![Big Grin](https://www.thirdgen.org/forums/images/smilies/biggrin.gif)
#5
That's not so "stupid". If you were going to short two of the wrong pins, those are probably the "smartest" ones to short, since you can't cause any real harm in doing so. You could have really done some damage if you chose a couple of other pins.
#6
Member
Join Date: Jul 2011
Location: Los Angeles
Posts: 178
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1987 IROC-Z Camaro
Engine: 305 LB9
Transmission: 700r4
Re: Diagnostic mode (shorted ALDL) doesn't work
So I hate to ask but what kind of damage could be caused by shorting the wrong pins? my car used to do diagnostic mode just fine half a year ago, but now it wont do it, and I fear I may have shorted the aforementioned wrong pins and hurt something. In any case, what are some common causes for no diagnostic mode?
Trending Topics
#9
Supreme Member
![](https://www.thirdgen.org/forums/images/ranks/tgo10.gif)
Re: Diagnostic mode (shorted ALDL) doesn't work
The ALDL is pin outs are configured like this (viewed from the front):
F = TCC Solenoid
I don't know if jumping these two would do any damage.
How do you know the ECM is not entering Diagnostic Mode? What does the SES light do with the key ON, engine OFF (ALDL not jumpered)? Steady light? No light? Flashing Code 12?
If you have a steady SES light and you jumper A-B what does the SES light do?
F-E-D-C-B-A
G-H-J-K-L-M
E = Serial DataG-H-J-K-L-M
F = TCC Solenoid
I don't know if jumping these two would do any damage.
How do you know the ECM is not entering Diagnostic Mode? What does the SES light do with the key ON, engine OFF (ALDL not jumpered)? Steady light? No light? Flashing Code 12?
If you have a steady SES light and you jumper A-B what does the SES light do?
Thread
Thread Starter
Forum
Replies
Last Post
db057
TBI
10
08-11-2015 10:11 PM