I purchased a beautiful '92 6 speed convertible 6 weeks ago from a retired gentleman who rarely drove the car. It has 18.5K miles on it. I myself only drive it on weekends. This past weekend I noticed the Service Engine Soon Warning Light come on while driving and also heard what sounds like a small backfire from the rear when shifting from 1st to 2nd. Can anyone offer any ideas on what the warning light may signify & if we're looking at big expense.

thanks

 

Surly someone will give you a comment. Ok, I will. If you follow the Forum and you should, you need to pull the codes. The connector is located in front of your right knee. Do a search to find out what pins to short out with a paper clip. I can't help you with that as my vette is a 96' and uses a OBD11 code reader.

When you have the trouble code, that will suggest what to look for first.

You need to purchase a Helms manual to fix problems. It can be purchased at www.helminc.com Good luck

 

On a 92 insert paper clip in terminals A ans G.
Turn on ignition switch ( do not start)
Codes will flash on digital speedometer. ( have pen and paper ready to write them down). If you miss codes just turn ignition key off and back on.
H before number means history code in memory. C means current code.
Post the codes and I will look them up in my 1992 FSM and tell you what they mean.

You can also put paper clip between terminals A and B and count the flashes on the check engine light but the above gives you much more info with regards to history and current.
You can also reset the codes when bridgeing A and G without disconnecting your battery. There is also other information available in this mode that I can walk you through after you pull the codes.

Good luck
Jerris

 

You need to short pins 1 & 2 or A & B. The top two on the right. All you need is a paper clip. Now turn the key to the run position, DO NOT start the engine. Your Service Engine Soon light will flash out a code 12 Blink,,,,, Blink, Blink. I think it flashes a 12, 3 times then it will flash out any stored codes. IE:32 = Blink,blink,blink,,,,,,,,,,blink,blink. I think each code will flash out 3 times then finish with a 12. Write down the codes and get back.
If you do any work on your car it would benefit you to buy the HELMS Factory Service manual set as elefkow suggested. There are other diagnostics built into the car to help in troubleshooting

 

Here's a very good site for you to visit!

http://www.c4vettes.com/ecm.htm

Great pictures, followed by procedures to pull codes, and a list of codes and what they mean. And yes, getting the factory service manuals is a MUST if you're going to turn your own wrench. Good Luck.

 

Ignore the rest this is the best way to do it.Here is a link to Bogus's write that says the same thing
http://www.c4guru.com/articles/CCMCodePull.pdf

 

Thanks all for replying. Brought my '92 in for diagnostic & had both O2 sensors replaced. They told me they also found intermittent stall & signal loss at PCM which I found strange since the car has never stalled on me. Beyond that, they say I also need a PCM (p/n 88999183) which is not available till June! Service Engine Light has not come back on since the sensors have been replaced.

Can anyone comment on the intermittent stall & signal loss at PCM and PCM replacement?

thanks

 

You can get one at Autozone.It is not unheard of for this to happen but I would clean the plugs on the ECM before I bought one.94 and up have a PCM.

 

Did you pull the codes? If so what were the codes? If not ask the service technition what the codes were.
If the O2 sensors were both bad, something caused then to go bad and you need to know what made them go bad or you will soon be replaceing them again.
The O2 sensors are only the messenger that tell you when there is a problem somewhere else that makes them read out of ramge, which caused the ECM to flash the service engine light.
Find out what the codes were and perhaps we can help you solve the problen that made them throw a code in the first place.
O2 sensors do go bad sometimes but at 19,000 miles they should not just go bad without something else causing them to do so.

And telling you now that you need to buy an ECM sounds like he thinks he has found a sucker and is getting ready to throw parts and your $$$$$$ at a problem that might not exist. From your post it sounds like your engine is running fine so there is nothing wrong with the ECM but he knows that just changing the O2 sensors is not cureing the cause of the check engine light and that you will soon be back with the light on again and he can soak you for a new ECM while he also charges you to fix the oroginal problem.
Be warned and armed with info. Ask him for the codes that he pulled as I explained in my previous post, or get ready to be a new vette sucker and give away laot of $$$$$$$$.
I guess you realise by now I hate "technitions" that take vette owners for a ride on their $$$.

Jerris.
PS Signal loss at ECM gives a particular code so unless you had one of these codes, they are full of S***. I have a 92 Factory Service Manual so post the codes and I will tell you what the FSM says they are and how to fix them.
Jerris

 

The SES light started coming on frequently last year when I drove my 1990 six-speed Corvette. Eventually, the engine began stalling. Finally, it would cut off about 20 seconds after the SES light came on. Then, the engine would run only 10 minute and then cut off and wouldn't start back for hours. Months went by and I had the car towed to a mechanic, and he replaced the ECM for $500, and that corrected the problem. If I had known it was the ECM, I could have purchased a re-built one for less than $100 at an auto parts dealer.
-- Eric

 

Thanks Eric, so I take it that ECM is the same as PCM? (I've only owned the car for less than 2 months, so I'm new to most of this.)

Bill

 

Yes they do the same thing as I said the 94+ have a PCM before that ECM.I would not do anything till you get another code.Once again I agree with Jerris GM mechs like to throw parts at stuff.If it is you ECM you will have definate codes appear.Get some contact cleaner and clean the plug on the ECM it is common for corrosion to cause issues.

If you have not done it go to www.helminc.com and order your factory service manual.You won't regret it and if you do someone her will buy it in a sec.

 

Jerris, the codes were 64 & 13. I sent you an e-mail under separate cover, did you receive it?

Bill

 

http://www.corvettedoctor.com/Code_Main.html
13 is the left O2 sensor
64 is right O2 sensor lean
Are these what you have now or what you had?

64 does not necessarily mean it is bad just lean.Do you have Datamaster to do a scan on it?That is what I would do at this point to see real time what is going on.Go to ALDLcable.com for a cable they have a link to Datamaster for a free download.

 

radioshack has the connectors for datamaster. I think you get 20 free trials and then 10 dollars for the rest

 

The codes are what was read by the dealer which led to the replacement of the O2 sensors. Not sure where or how they got a reading of intermittent stall & signal loss at PCM, which they indicated was evident after replacing the O2 sensors.

What is Datamaster?

Bill

 

The above is correct for the codes mentioned. In looking at the FSM does mention that a bad ECM can be the cause of these codes. However as the two O2 sensors are on two different circiots within the ECM and both are throwing codes at the same time leads me away from a bad ECM connection or a bad ECM.
Besring in mind that it could possibly be the ECM I think it is advisable to eliminate any other sources first.

As they are both setting a code at the same time they are both experiencing the same conditions at the same time and that leeds me to suspect a problem in the fuel supply system causing a lean condition because a lean condition can move both O2 sensors out of range.

You really need a Tech 1 or datamaster scan to test if the voltage to the o2 sensor is between 350mV and 550mV. If it is not you have a faulty ECM, if it is within this range there are a number of things to gheck.
If you do not have a scanner you may want to assume it is within this range and do the following tests:

1. Make sure both pigtails are not touching the exhaust manifolds (unlikely as they are seperate circuits and both sensors set their code)
2. MAP sensor. A manifold absolute Preassure sensor that causes the the ECM to sense a higher than normal vacium, will cause the system to go lean and both O2 will throw a code. Discommect the MAP sensor and if the lean condition is gone (no more code) replace the MAP sensor.
3. Fuel Contamination from water in the gas tank or really old gas (you dont drive the car mucm so it could be either) can cause a lean condition.
4 Dirty fuel injectors will also cause a lean condition. Put some injector conditioner and new gas in the tank and put some miles on the car.
5 Low fuel preassure can also cause a lean condition. Hook up a guel guage and tape it to the windshield and watch it while you are putting some miles on.
5 AIS systen can cause a lean condition if the air pump is operating in close loop. Let the engine idle until it warms up and goes into closed loop and check to see if the air pump is pumping air into the exhaust by disconnecting the hose on the exhaust side of the selonoit that cuts off the air.
6 If there is an exhaust leak above the O2 sensor the exhaust can pull extra iar into the exhaust pipe and cause the O2 sensor to register a lean condition. (unlikely as this would only affect one sensor and both has codes) This is easy to check by reving the engine in idle and listening or feeling for exhaust escaping when you plip the throttle.

There is alot of things listed above that you can check without a scanner or taking it to a dealership for a scan. Check these and report back. Your problem may be connected to the fact that you or the previous owner didnt drive the car very much. Take the car out with a full tank of new gas and take it through its paces for some miles and see if it clears up, these cars like to be driven and driven hard occasionally.

By the way I did not get your PM yet.

Hope this helps, keep at it and you will be rewarded with the pride of having fixed the problem yourself, and report often so that we can narrow down the possibilities.

Jerris

 

Pretty much my point without the in depth explaination.

www.aldlcable.com get a cable and datamaster download and hook it up to a laptop. It plugs into your ALDL plug under the dash on the drivers side.It logs pretty much everthing that goes on in your engine from the ECM.You will be able to diagnose if you engine is running lean or not.Once you get a log you can post it and we can tell you what is up.

 

My O2 sensors have been replaced beaucoup times, no one can figure it out. Can I hook this up even if I currently have no SES light as I've got two new sensors (on the same side)?

I'm really sick of this problem. Last one lasted 1200 miles.

 

Yes you can, and you should.

Jerris