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I got a 1982 Corvette about 5 years ago from a little old lady (Mom) that has owned it since 84. It has had a pretty sheltered life.
About year ago, as I was pulling out of the neighborhood, it just died. Waited about 2 minutes or so, it fired back up and I limped it home, took a few start/stops, but made it. Figured it was the fuel pump, so I replaced it with ACDelco EP241, for more fuel pressure.
Have driven it various times over the year, not much, maybe once/twice a month, but never had any problems. It would start right up and cruised along, no issues. The last time it was on the road, it drove fine, no issues, drove it around and then parked it in the garage. Then week or so later, hoped in to take it for a spin and it died backing out of the garage. I figured that it must be the fuel filter, so I replaced that. Now the car is acting differently
1. Car starts fine and was able to cruise around the ‘hood, no problems. Put it up for the day. Next day, tried to go out again, this time it stalled out after putting it in gear. Parked it for the day, and used other car.
2. Next day, fired up the car and let it idle for about 10-15 minutes. Shut off the car and then tried to restart it. It wouldn’t restart normally. When I finally got it restarted, it was running really rich, the exhaust smell of gas was pretty potent.
3. Day after that, it fired up fine, no bad gas smell, but stalls when put it in gear.
I am not getting the “check engine” light, so pulled the bulb and tested it, it is good. Not sure what the little circuit board is that the bulb plugs into, (and curious on why it has 3 connections, for a bulb that needs 2 wires), but the bulb is good.
If I jumper A-B on the ALDL and I get no blinking, not even the “12”. I can hear something clicking when I add/remove the jumper, so at least I know my jumper wire is making contact with the terminal pins. The manual (page 6E-21) says check Circuit 419. Is there an easier way to get to Pin 20 on the ECM connector then becoming a contortionist and trying to get visibility to the connector. I am half temped to pull the passenger seat to make getting to the ECM connector easier.
I want to see if the ECM is throwing any codes, before I just guess and start replacing the oil pressure switch, the coolant switch, and other various things I have seen mentioned in various posts, it would be nice to know what the ECM thinks is wrong. Is there any test connections points inside the engine compartment. It would be nice to test the various sensors under the hood, then determine if there is a wiring issue.
Also, is there a fairly inexpensive code scanner, that can connect to the ALDL, instead of using the check engine light? I don't want to spend $2K on something, but couple hundred on a decent reader might be worth it.
Is the check engine light on during key-on/engine-off? Kind of sounds like the ECM is bad or possibly the ECM connection. Did you try to disconnect the battery for a bit and then retry reading the codes?
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Battery box fuse is the main power fuse for the ECM. If the fuse is blown, the ECM will not power up and engine will not start and CEL light will not come ON. If that fuse is good and CEL light is good, the ECM is bad.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Originally Posted by Jtmirolli
The engine light does not come on, when turning the key switch to "on" but not starting the car.
Bought a used Snap-on MT2500 scanner and going to plug that in and see what it can tell me.
I'm willing to bet that you will get nothing with the scanner if your CEL does not come ON and bulb is OK. There will be NO communication between the two..
Well, the scanner came in and it was a bust.... since it didn't have the GM-1 adapter needed. :-( The plus side is my OCD/AR self got a chance to de-grease/clean the scanner all nice and pretty, and actual read the manual before I just plugged it in and started hitting buttons. :-)
I think I figured out that the "Diagnostic Check Connector" shown on page 8A-87 of the service manual is the ALDL port, under the ashtray. If that is the case, I should be able to take pin C to ground, and the Check Engine Light should turn on. If I can toggle the engine light manually, then that kind of leans towards the ECM not controlling the light, which is bad.
I am the most incompetent, short-bus riding, window licking, pea-brain, half-wit, moron in the whole forum right now. For some reason I had it in my brain the the CEL is the top-right indicator, when looking at the center console. I pulled the bulb out, put a light behind the panel, it was “low fuel”. The CEL is the lower-left.
There is no good way to get to the CEL bulb without taking half the car apart, but when I put a test light on circuit 419, it does turn on when I turn the ignition on, then goes back out after the car has started. So at least the ECM is controlling the light circuit. The test light wasn't as bright as when I tried it on the cigarette lighter, just to make sure that I had a good ground connection. Jumping ALDL pins A & B didn't get me any flashes with the test light on Pin C. I would have though I would have got the 12 code, but trying to get jumpers and test probes through the ashtray opening, I might not have made good connections. I will try using the scanner, when the GM-1 ODB adapter comes in on Monday.
I guess this weekend’s project is taking apart the center console to get to the CEL bulb, and replace that. Then we are back at square one.
Last edited by Jtmirolli; Sep 29, 2022 at 07:58 PM.
I am the most incompetent, short-bus riding, window licking, pea-brain, half-wit, moron in the whole forum right now. For some reason I had it in my brain the the CEL is the top-right indicator, when looking at the center console. I pulled the bulb out, put a light behind the panel, it was “low fuel”. The CEL is the lower-left.
There is no good way to get to the CEL bulb without taking half the car apart, but when I put a test light on circuit 419, it does turn on when I turn the ignition on, then goes back out after the car has started. So at least the ECM is controlling the light circuit. The test light wasn't as bright as when I tried it on the cigarette lighter, just to make sure that I had a good ground connection. Jumping ALDL pins A & B didn't get me any flashes with the test light on Pin C. I would have though I would have got the 12 code, but trying to get jumpers and test probes through the ashtray opening, I might not have made good connections. I will try using the scanner, when the GM-1 ODB adapter comes in on Monday.
I guess this weekend’s project is taking apart the center console to get to the CEL bulb, and replace that. Then we are back at square one.
Since you're going to be taking the interior apart to get to the center console gauges and warning lights, you might as well replace all of your bulbs, ohm out your gauges to make sure they are accurate (use a 12v power source and an adjustable rheostat), and replace any parts in there that are needed.
Pulled the center console gauge set, to change out the bulbs. The CEL bulb tested good, but I went ahead and replaced it with an LED bulb instead. Plugged the set back into the harness and I now get the check engine light coming on when the key is turned to on. So at least I got that going for me.... I did notice that the traces on the circuit board are coming off the plastic, at the harness connection point. That might have been my issue originally. When I put the harness connector back on the gauge set, the traces to the harness plug might have gotten misaligned.
However, I noticed that there is some gaffers tape covering one of the traces for the oil temperature light. I created another topic, Console circuit board since this topic was concerning the CEL.
In case you all were wondering about the MT2500 scanner, got things hooked up and it is working pretty good. Gives a good bit of information on various sensors, like telling me that my TPS is reading a little low, at .46V, instead of .525, the 02 sensor reads about 470 mV, when running, etc.
Two things do bother me though:
1. The scanner is telling me that the ECM is in “Limp mode”
2. The ECM is staying in “open loop" mode, unless I get the RPMs up to around 2K. Maybe I need to let the car warm up for 10-15 minutes and see if that helps.
Been trying to find any information about limp mode and what could cause that. I get no codes on the scanner, or counting the CEL blinks. Not sure how it decides to go into limp mode, and what needs to happen, to get out of that mode.
Let me rephrase my last comment. If I short A&B, then the CEL light blinks "12" (which I think is "all good") and then I don't get any *other* codes after that. I get the 12, just nothing else
In case you all were wondering about the MT2500 scanner, got things hooked up and it is working pretty good. Gives a good bit of information on various sensors, like telling me that my TPS is reading a little low, at .46V, instead of .525, the 02 sensor reads about 470 mV, when running, etc.
Two things do bother me though:
1. The scanner is telling me that the ECM is in “Limp mode”
2. The ECM is staying in “open loop" mode, unless I get the RPMs up to around 2K. Maybe I need to let the car warm up for 10-15 minutes and see if that helps.
Been trying to find any information about limp mode and what could cause that. I get no codes on the scanner, or counting the CEL blinks. Not sure how it decides to go into limp mode, and what needs to happen, to get out of that mode.
I am looking for some kind of scanner myself.
A review by you is liked.
More info would be nice, when you solve your issue, like fuel ratios and timing advances.
thanks
In case you all were wondering about the MT2500 scanner, got things hooked up and it is working pretty good. Gives a good bit of information on various sensors, like telling me that my TPS is reading a little low, at .46V, instead of .525, the 02 sensor reads about 470 mV, when running, etc.
Two things do bother me though:
1. The scanner is telling me that the ECM is in “Limp mode”
2. The ECM is staying in “open loop" mode, unless I get the RPMs up to around 2K. Maybe I need to let the car warm up for 10-15 minutes and see if that helps.
Been trying to find any information about limp mode and what could cause that. I get no codes on the scanner, or counting the CEL blinks. Not sure how it decides to go into limp mode, and what needs to happen, to get out of that mode.
limp mode is caused by a trouble code and will have Fixed timing and limited performance. What makes you think you’re in Limp mode ?
the .46V instead of .525 is very minor and not hurting anything so don’t waste time , if voltage goes up nice as you floor it then you’re done with the TPS
dead or lazy Oxygen sensor is what causes the vehicle to be in Open Loop or have to rev high to get to closed loop
When in Closed Loop you should see the 02 swing back and forth from low voltage to high voltage with lots of Cross counts if working correctly with a good O2 sensor
I don't think that scanner is working correctly with your 82. There is no specific code that will tell it that's in "limp mode". Since you're getting a code 12 with the jumpers the ECM is fine.
When I worked at GM I found an engineer that worked on the Crossfire and he recommend the Peerless 350. I found one cheap on e-bay. Perfect condition but no instructions. Still don't know how to use all the features but it reads the basics just fine.
His tool is working correctly , on older CCC some computers goes in limp do not drive mode with scan tools hooked to them which is probably what happening in this case, code 12 is no tach signal and appropriate since reading codes the engine is not running . limp and open loop are the same or very similar. For the OP I would start with a fresh 02 sensor and restart the learning process for the computer
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
No "check engine" light to see what is wrong
Someplace to start checking.
