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ShaneL
03-29-04, 12:03 AM
Is there an economical way to read the DTC codes without having to shell out $500? This stupid light has ben giving me greif for the whole week and I can't figure it out.

CKA_Racing
03-29-04, 12:47 AM
Try an AutoZone parts store. They will read the codes for free. Short of that, Sears sells a OBDII scanner reader that will give you the codes, it also is able to reset the light. The scanner comes with a book. this is the one i have $149.00 bucks

http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00947059000

Sears item #00947059000
Mfr. model #CP9135
Also plenty of web sites out there to give you what the codes means.
http://www.obdII.com (http://www.obdii.com/)

Autoxray scanner are good scanners.
http://www.etoolcart.com/autoxray-scanner-G1.htm

Home page
http://www.autoxray.com/products.aspx

Scan tool report:
http://www.autoxray.com/dnload/ScanToolReport.pdf

HTRK-1
03-30-04, 10:23 PM
Because you're car is a 1996, this may work for you...Not bad for under $40.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46030

CKA_Racing
03-30-04, 10:27 PM
Because you're car is a 1996, this may work for you...Not bad for under $40.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46030
You will still need to reset the light, this tool will not reset it.

HTRK-1
03-30-04, 10:46 PM
If you correct the problem...won't the light go away? Also, if you disconnect the battery for a while, won't this erase any stored codes?

BigRed
03-30-04, 10:59 PM
Two things about "reseting" the computer.

One: If your computer holds a static memory it will not clear by pulling the battery. You will have to reset it by scanner (Any shop can do this pbly free of charge).

Second is you CAN reset it but the problem is SO persitant it will register immediatly.

So better off buying a cheap code grabber establishing your problem then fix it. Then worry about the trouble light.

If you car doing anything funny? Running rough or Bad gas mileage?

Seahorse51
03-30-04, 11:46 PM
I think you are right. According to Chilton's: "Stored fault codes may be erased from memory at any time by removing power from the ECM for at least 30 seconds."

Hope this helps.

ShaneL
04-08-04, 04:38 PM
I was able to recover the cosed using this technique and I would like to know whast they stand for now. I got the following from module 1 the CCM. H31, H33, H35, AND H37.

Thanks for the help and I hope that some others can use this information.


In 1994, Chevrolet went to a 16 pin ALDL connector in preparation for the federally mandated change to the much more capable OBD-II (On Board Diagnostics - Version 2) system.

As with the 1990-1993 model, you can display codes on the speedometer but the pins to be shorted are different:

http://www.c4vettes.com/94_96_code_display.JPG

Beginning in 1994, you short pin "12" to pin "4" and once again turn the ignition switch to "On" without starting the engine.

The speedometer will display any codes using the same protocol as the 1990-1993 model but there are some changes in the designation for the modules plus additional modules are added:

Module "1" is still the CCM module.

Module "4" is now called the PCM module (Powertrain Control Module) because automatic transmission computer control was added to Engine Control Module in 1994.

Module 7 (on the 1996 model only) is the RTD module. (This is the Real Time Dampening module which replaced the Selective Ride Control module in 1996).

Module 9 is the ABS/ASR module number from 1994 through 1996.

Finally, Module "A", the DERM (Dynamic Energy Control Module --- the air bag control module) will be requested to show any codes.

Just like the 1990-1993 display, you read the codes on the speedometer and read the module number on the trip odometer.

Again, you can cause the codes to repeat by turning the ignition off for five seconds and then back on.

Turn the ignition off and remove the short to restore normal operation.

FX GS
04-08-04, 05:49 PM
A "H" preceding the fault code number means a HISTORY fault code and the fault IS NOT present at this time. In other words, you're good to go and enjoy your car

CKA_Racing
04-08-04, 05:51 PM
I was able to recover the cosed using this technique and I would like to know whast they stand for now. I got the following from module 1 the CCM. H31, H33, H35, AND H37.

Thanks for the help and I hope that some others can use this information.
You did this on a 96 OBDII?

KOPBET
04-08-04, 07:53 PM
I was able to recover the cosed using this technique and I would like to know whast they stand for now. I got the following from module 1 the CCM. H31, H33, H35, AND H37.

Thanks for the help and I hope that some others can use this information.Module 1 CCM DTCs

31=LCD Data Circuit shorted to B+ or CCM internal open.
33=Data Clock Circuit shorted to B+ or CCM internal open.
35=Data Strobe circuit shorted to B+ or CCM internal open.
37=M Clock Circuit open or shorted to B+ or CCM internal open.

Like FX GS said, the H indicates a history code. Forget about it.

If you want to read PCM codes, get access to a scan tool. Try Auto Zone. They'll do it for free.

bnhynum
04-17-04, 05:22 PM
Where did you get those code descriptions. I'm getting C12 on Module 1 then H48 and H42 on module 4.

KOPBET
04-17-04, 09:49 PM
Where did you get those code descriptions. I'm getting C12 on Module 1 then H48 and H42 on module 4.

You can find them on the web or you can purchase a GM shop manual for your year car.

12 is the code for "no codes".

Module 4 is the PCM.

Skant
04-19-04, 01:22 AM
Whoa whoa whoa! I also have a 1996, and I've been through this.

1996 was around the time that the switch from OBD1 to OBD2 happened. Many manuals say that the 1996 Corvette does not respond to OBD1 methods (like that shorting the pins trick)... but in fact it does.

HOWEVER...

You're only talking to _part_ of the computer. You're only seeing some of the elements that happen to still be compatible with OBD1. It doesn't _really_ work all the way... that's why GM says you can't use this mode. It's half baked. A remnant. A partially functional backward compatibility mode that they didn't disable completely. It doesn't really work, but it looks like it does.

And most importantly, it probably won't show you the information you're looking for. Even though the code is real and is not historical.

I'm afraid that if you want to know what's going on with your 1996, you'll need to get access to a proper OBD2 scanner. Sorry. No other method will work correctly.

OBD2 is dramatically more advanted than OBD1. And it has a zillion more fault codes. That's why any particular fault you get isn't likely to have any backward compatibility to appear on the half baked OBD1 backward compatibility mode. It's pretty useless. When I tried it on mine, the OBD1 stuff reported no fault codes at all. When clearly there was. In your case, you found some old historical OBD1 compatible codes, but that's not why your engine light is on. You just can't see the OBD2 codes that are tripping that light using that method.

Hope that helps...

- Skant

KOPBET
04-19-04, 07:46 AM
Whoa whoa whoa! I also have a 1996, and I've been through this.

1996 was around the time that the switch from OBD1 to OBD2 happened. Many manuals say that the 1996 Corvette does not respond to OBD1 methods (like that shorting the pins trick)... but in fact it does.

HOWEVER...

You're only talking to _part_ of the computer. You're only seeing some of the elements that happen to still be compatible with OBD1. It doesn't _really_ work all the way... that's why GM says you can't use this mode. It's half baked. A remnant. A partially functional backward compatibility mode that they didn't disable completely. It doesn't really work, but it looks like it does.

And most importantly, it probably won't show you the information you're looking for. Even though the code is real and is not historical.

I'm afraid that if you want to know what's going on with your 1996, you'll need to get access to a proper OBD2 scanner. Sorry. No other method will work correctly.

OBD2 is dramatically more advanted than OBD1. And it has a zillion more fault codes. That's why any particular fault you get isn't likely to have any backward compatibility to appear on the half baked OBD1 backward compatibility mode. It's pretty useless. When I tried it on mine, the OBD1 stuff reported no fault codes at all. When clearly there was. In your case, you found some old historical OBD1 compatible codes, but that's not why your engine light is on. You just can't see the OBD2 codes that are tripping that light using that method.

Hope that helps...

- Skant
Isn't that what's been said, i.e - get a scan tool for the PCM stuff (for shanel)? :confused CCM codes discussed do work well for many things.

(If you are talking about bnhynum,he does have a 95.) :beer

ShaneL
04-19-04, 07:51 AM
I'm gonna take the plunge and get AutoTap for my laptop.

bnhynum
04-19-04, 09:12 AM
googled this today.

http://www.crossedflags.com/nuke/html/modules.php?name=Downloads&d_op=getit&lid=16

Skant
04-19-04, 01:38 PM
KOPBET: Reading it again, I see you did say that. It hadn't been clear to me. When I read the thread, it sounded like the pin shorting method had been used, and based on that he was deciding that he'd already found the codes he was looking for.

I think he has not. He needs a scan tool. And I wanted to make that clear.

Apologiies for misreading your post. You had already said that.

- Skant