Diagnostic port
Thread Starter
5th Gear
Joined: Sep 2020
Posts: 5
Likes: 0
From: Texas
Diagnostic port
I’ve got a 1995 LT1. It keeps reading a check engine light and I wanted to have the code read. But I can’t find the diagnostic port. I see where it used to be mounted but I can’t find the port anywhere. Surely it wasn’t removed was it??
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
As the above poster said, it may have been unscrewed and accidentally shoved up under the dash panel by someone at some point. Remove all the 7mm bolts that hold the knee panel on (there are some on the side facing the door, and the rest are where the panel meets the lower dash), then wiggle it free slowly. Do not yank on it--the floor courtesy light is plugged into the car, so to get the panel free all the way you need to unhook it first. Then the panel will come free.
Thread Starter
5th Gear
Joined: Sep 2020
Posts: 5
Likes: 0
From: Texas
Yeah I’ve already taken the panel off. I still can’t find it but I’m gonna try to crawl up in there with a better flashlight. So far I can’t find anyone to read it anyways. Apparently a 1995 has an OBD1.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Option 1: https://tech.corvettecentral.com/201...trouble-codes/
Option 2: Buy a $50 16-pin USB-to-ALDL cable and plug it into a laptop and use free software such as EEHack to communicate with the car and check the codes as well as do real-time datalogging.
Team Owner
Joined: Jul 2004
Posts: 28,374
Likes: 3,260
From: Hartford WI
Does it? I thought that 96 has an OBD2 port while somewhere earlier like 93 to 95 they have the OBD2 port but it still runs on OBD1?
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Pro
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From: Liliha Bakery stuffing my face with coco puffs!
My ALDL port is not connected in the stock location. Actually it's just hanging there with the 1320 BT cable hooked up to it. Idk if PO attempted to stick it under the center console but wouldn't reach/fit.
Last edited by stew86MCSS396; Sep 29, 2020 at 04:52 AM.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Would THIS work? The full OBD 1 version works on my 91.
And yes, the 94-95 use a 16-pin port with the same shape as an OBD2 port, but the pinout is not the same as OBD2, and the communication protocol is 8192 Baud ALDL (OBD1).
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
How about use the onboard diagnostics? Nothing required except a jumper wire and the know-how to do it.
Here's a link to the text that gives you the "know-how".
Here's a link to the text that gives you the "know-how".
You have two options once you do find it.
Option 1: https://tech.corvettecentral.com/201...trouble-codes/
Option 2: Buy a $50 16-pin USB-to-ALDL cable and plug it into a laptop and use free software such as EEHack to communicate with the car and check the codes as well as do real-time datalogging.
Option 1: https://tech.corvettecentral.com/201...trouble-codes/
Option 2: Buy a $50 16-pin USB-to-ALDL cable and plug it into a laptop and use free software such as EEHack to communicate with the car and check the codes as well as do real-time datalogging.
Team Owner
Joined: Jul 2004
Posts: 28,374
Likes: 3,260
From: Hartford WI
Reflashing, I'd pass unless you have some desire to mod and heavily. I'd rather have data than codes and it's cheap. 80 dollars and a smart phone we all have gives you a scanner. I carry that with me but use the other two when I am home.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Reflashing allows for some wonderful things even if you're stock. For example, on the autos, you can alter all the shift points and access an on-the-fly switchable shift pattern. So you can have the car shift one way on the road, and another way at the track. It lets you control MIL errors, for example suppressing the knock sensor error if the notoriously-shoddy resistor in your knock sensor fails. You can have the cooling fans kick in at lower temps to control engine temp, and have them kick out at a different speed for cruising. You can flash in code that replaces the inaccessible OBDII test code with high-speed datalogging code instead. And of course you can adjust the factory MAF and VE tables to better match your specific vehicle. And those are just the start.
You would have to actually be interested in taking your car into your own hands, which not all Corvette owners are. But you don't have to be going *****-to-the-wall with mods to get benefits from altering the code.
You would have to actually be interested in taking your car into your own hands, which not all Corvette owners are. But you don't have to be going *****-to-the-wall with mods to get benefits from altering the code.
Last edited by Nomake Wan; Sep 29, 2020 at 12:02 PM.
Team Owner
Joined: Jul 2004
Posts: 28,374
Likes: 3,260
From: Hartford WI
Reflashing allows for some wonderful things even if you're stock. For example, on the autos, you can alter all the shift points and access an on-the-fly switchable shift pattern. So you can have the car shift one way on the road, and another way at the track. It lets you control MIL errors, for example suppressing the knock sensor error if the notoriously-shoddy resistor in your knock sensor fails. You can have the cooling fans kick in at lower temps to control engine temp, and have them kick out at a different speed for cruising. You can flash in code that replaces the inaccessible OBDII test code with high-speed datalogging code instead. And of course you can adjust the factory MAF and VE tables to better match your specific vehicle. And those are just the start.
You would have to actually be interested in taking your car into your own hands, which not all Corvette owners are. But you don't have to be going *****-to-the-wall with mods to get benefits from altering the code.
You would have to actually be interested in taking your car into your own hands, which not all Corvette owners are. But you don't have to be going *****-to-the-wall with mods to get benefits from altering the code.
Drifting
Joined: Jun 2018
Posts: 1,678
Likes: 229
From: Michigan
In my truck, I have the tune box you can switch on the fly but that is for a couple of tow tunes and a high idle and a ***** to the wall tune. I guess I personally don't see the point of doing all that work and the cost of the hardware for a one off deal so I would hire a programmer to do it for me but if you just want to do it, I suppose there would be some sort of justification.
Until I change something else and just do the tuning update myself and if it's something major I am only out the dyno rental fee and not the programmer's time, again.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
In my truck, I have the tune box you can switch on the fly but that is for a couple of tow tunes and a high idle and a ***** to the wall tune. I guess I personally don't see the point of doing all that work and the cost of the hardware for a one off deal so I would hire a programmer to do it for me but if you just want to do it, I suppose there would be some sort of justification.
If it was $400 or something you'd have a point, but this is really just not a big deal. And why use an external controller on a 4L60E when the PCM does it right out of the box? That seems silly.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Team Owner
Joined: Jul 2004
Posts: 28,374
Likes: 3,260
From: Hartford WI
Because the hardware and software required to make those changes is $50? "All that work and cost of hardware" is...practically nothing whatsoever. I've tuned both my car and my dad's car. The cable has paid for itself.
If it was $400 or something you'd have a point, but this is really just not a big deal. And why use an external controller on a 4L60E when the PCM does it right out of the box? That seems silly.
If it was $400 or something you'd have a point, but this is really just not a big deal. And why use an external controller on a 4L60E when the PCM does it right out of the box? That seems silly.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
It is more than $50 according to THIS article so I'm not sure. I don't know what a laptop running an older version of windows goes for since both our laptops are Windows 10. And then there is the time commitment to learning how to tune. If you are making a couple changes, maybe not so much but what to do with the hardware after you are done and not need it?
Cable: http://aldlcable.com/products/aldlobd2u.asp ($60; my bad, off by tenbux)
Laptop: Any (yep, even Windows 10 works just fine!)
Software: Free (TunerPro is free, EEHack is free, Flashhack is free)
But yes, you would need to learn how to tune if you want to modify the engine. But learning how to tweak isn't hard at all, and it can be used for diagnostic purposes and datalogging as well.
So again, yes, it depends on what you want to get out of it. But a $60 investment is a pittance for the amount of awesome stuff you can do with the 94-95 Corvette PCMs.
OP, have you found your ALDL wiring yet?