72Shark

Picked up a sweet 94 LT1 Coupe last week, 1-owner, clean.

The "only" think not quite 100% is this nagging little hesitation/skip/stumble at idle that happens intermittantly. I've searched the forum for the "paper clip" trick to pull codes, but I'm new to the C4 scene (C3'er and C5'er) and need some help how to do this??? I have my paper clip tuned up and ready to go!

Also, where can I find the "index" of what the codes are?

Thanks, glad to be a C4'er now too!!

SilverBeast

Go here:
http://forums.corvetteforum.com/show...read+obd+codes

Photomania

I have a Haynes c4 repair book, and it lists the codes. I tried a small wire and I tried a paper clip in the diagnostic center beneath the dash in my 1990 six-speed C4. I did exactly what Haynes said to do, but I got no codes. After several attempts, I gave up. -- Eric

jabez

What do you mean "you got no codes"?
Did you remember to turn key to on position?
You should have seen your dash with flashing dashes after shorting A & B.

Try this too. Short A & G. You should see numbers flash on your speedometer.

rws.1

If you have an Autozone parts store near you drop in for a free key that plugs into the diagnostic plg. It's a lot easier that a paper clip

vettman96

Cool, I'm going to Autozone today..................

72Shark

Paper Clip worked!!!

I got: G12, H64, and H72. Now what are these????

72Shark

Typo...that's a C12 not G12.

Steel Blue 91

C12 is a sort of check code.

Any code with an "H" in front is a history code. That means that a particular sensor was out of range at some point, but not now.

DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.

DTC #72: Vehicle Speed Sensor Loss.


Got them from here:

http://www.corvetteactioncenter.com/....php?qstId=150

Again, they are history codes and unless you have the SES light on now, you can disconnect the battery for a few min and that should clear them from memory.

MikeC4

....somewhat.....but check your codes again in about a week or two of driving.....'cuz a bad O2 sensor does not continually illuminate your check engine lamp...usually what happens if an O2 sensor is toast is this:
1) you may notice sluggish and bumpy idle at operating temperature(closed loop operation)
2) if your looking the check engine light will turn on for short time
3) the PCM detects bad O2 sensor and stops taking input from it
4) the idle will then improve somewhat: PCM uses programmed lookup table for AFR values
5) History code is stored for the bad O2 sensor...

...anyway, don't just ignore the fact that you had error codes once you clear them. Clearing the codes doesn't fix the problems!

DougSilver

You also have to take note as to under which testing "module" the codes appear. For example if H64 shows up under the ABS testing module it indicates problems with the throttle position sensor.

DougSilver

Join the party--I have had a nagging miss on my 95 for quite some time. The opti and wires are less than 2 years old but I found corrosion where the coil wire plugs into the coil. Cleaned that up and the miss went away for a few days but is now back. I wish I had a nickel for every post on this board from someone with an LT1 that has missing, stumbling, hesitation problems. Quite a testament to GM quality.

72Shark

Thanks to everyone for all the help and advice! I appreciate it....and guess what.....IT WORKED!!

I've owned the car for a week now, and the advice from the C4 section has really made the "repairs" a breeze. I pulled the IAC from underneath the "throttle body" and it was all gummed up. I spent a few minutes cleaning it up and then polished the tip. I then cleaned the electrical connections on the IAC and the wire harness, reinstalled, and VIOLA!...runs like a dream. I ran it on Saturday evening and on Sunday with no stumbles or hesitations, so I'm calling it "fixed".

So far it has been:
New BF Goodrich KDW's
Lifetime 4-wheel alignment
New Bosch spark plugs
New Shocks
One "high-tech" code scanner (paper clip)
Clean-up of IAC
....and I've done it all except mount the new tires on the wheels. Runs perfect, and my only project left is to tint the windows (old tint has some peeling). Thanks Everyone!!!!

Joeythedog

Hi new here...the paper clip worked great on my 1994 corvette LTI....Module 1..C12...Mod 4 H64...Mod 9 H64 A--- 1.0 next and i did nothing manually at this time, turned key off took out paper clip....Now the car has 91000km or near 57000 miles..3yrs ago i had wires/plugs/fuel filters and the RF 02 sensor replaced in 2013 0r approx 10-15k ago...reading todays code H64 the code states Bank 2 RF Heated Oxygen señsor #1 Circuit lean?....This appears to be the same sensor replaced a few years/km ago yet none of the others have been replaced since i owned the vehicle for 20 plus years..is this possible the newest replaced sensor went **** ups again?..or am i reading this incorrectly? The vehicle has never been driven nor been in rain etc,just sunny days and taken out for a spin even in winter months if no snow(approx bi weekly)..Thanks

aklim

If you change one sensor, you should change all. When one shoe is worn out, how far along is the other one usually?

belairbrian

when I got my 92 I tried to use the paper clip but no joy.
couldn't believe it then I put a meter on the paper clip and it didn't conduct electricity WTF how can a paper clip not conduct?

seems our box of paper clips had a clear plastic coating, stripped the ends and it worked
upside is my jumper is insulated

aklim

Relying on the codes is fine if there is no other way. I carry my scanner to read the code to guide me for what to see in the data stream