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Discussion Starter · #1 ·
Does the 83 ECM have a sleep mode with key off, or does it dray a current all the time, if so how much should it be?
 

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Does the 83 ECM have a sleep mode with key off, or does it dray a current all the time, if so how much should it be?

First off there isn't a 1983 Corvette. Technically there is one in a museum but there wasn't a 1983 sold as a model year. 1982 was the last year for the C3 Corvette and 1984 was the first year for the C4.

As I understand it, there is a minuscule voltage draw by the computer, but it's so small it's almost not noticeable.
 

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Just to clarify (cause I know others will too) that was no '83 Corvette. They carried over the '82 until the release of the all new '84.
To answer your question: Yes, ECM's will pull a small amt of current when not in use. I believe it's in the millivolts range, so depending on the condition of the battery, it should be able to sustain for several weeks without assist.
If you're getting a more severe battery drain, trace it by pulling fuses until you've found the guilty circuit. Then find the component from there.
:cheers:
 

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Does the 83 ECM have a sleep mode with key off, or does it dray a current all the time, if so how much should it be?

I see your a new member and this is your first post so a big welcome to DC :D

If you would let us know more info on what car you are working on and any mods it would help in answering questions.

And once again welcome :cheers: Mark
 

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Discussion Starter · #6 ·
The current draw is 2.3 A. with all courtesy lights, accessories and alternator is disconnected. There is no draw with the ECM fuse in the Batt compartment pulled. With the fuse in, the ECM is noticeably warm the next day. Just wondering it that too much pull, the Batt is new and will drain to a no start state in a week.
 

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The current draw is 2.3 A. with all courtesy lights, accessories and alternator is disconnected. There is no draw with the ECM fuse in the Batt compartment pulled. With the fuse in, the ECM is noticeably warm the next day. Just wondering it that too much pull, the Batt is new and will drain to a no start state in a week.
I have no direct experience with an 82 ECM, but as an electronics engineer, drawing 2.3A is way more than the few millivolts (milliamps!!!) referenced by the other DC members, and I don't think the ECM should be getting warm when the car is off sitting overnight, a few milliamps won't warm up anything, but 2.3A will! :surprised

2.3A @ 12Volts = 27.6 Watts that quite a bit of power for something that is supposed to be "off".

I would start looking for a new ECM, before whatever component that is starting to fail, lets go completely, stranding you out in the middle of nowhere.
 

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The current draw is 2.3 A. with all courtesy lights, accessories and alternator is disconnected. There is no draw with the ECM fuse in the Batt compartment pulled. With the fuse in, the ECM is noticeably warm the next day. Just wondering it that too much pull, the Batt is new and will drain to a no start state in a week.

I do have a wiring schematic for your year model ,but it does not show the internals on the ECM. On many ECMs the circuit that has power when the key is off feeds other components. It could also have a low level drain to ground through the wiring. I would put the amp meter back on it and in stead of unplugging the fuse unplug the wiring harness and see if the drain goes away. The way GM designs their electrical systems it could be something other than the ECM. The schematic also shows the fuse for the ECM also feeds ESC and it is a pink/black wire. I am not familiar with ESC so try unplugging ESC and see if it goes away. The car alarm may be fed through the ECM this would be an example of the ECM feeding a circuit with the key in the off position. Happy hunting Mark:thumbsup:
 

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I have no direct experience with an 82 ECM, but as an electronics engineer, drawing 2.3A is way more than the few millivolts (milliamps!!!) referenced by the other DC members, and I don't think the ECM should be getting warm when the car is off sitting overnight, a few milliamps won't warm up anything, but 2.3A will! :surprised

2.3A @ 12Volts = 27.6 Watts that quite a bit of power for something that is supposed to be "off".

I would start looking for a new ECM, before whatever component that is starting to fail, lets go completely, stranding you out in the middle of nowhere.
As a fellow electronics engineer, (or a graduate waiting to become one) I see that everything this guy said is dead spot on. (especially that current draw is milliamps) I also would agree that unplugging the ECM itself apart from it's fuse and measuring current would help isolate the issue greatly. It should not get warm at all when off, almost certainly meaning ecm has an issue. Curious though, does it run well?

~wd-40:buhbye:
 

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I too almost suggested unplugging the ECU to determine if it's the problem or if something else on that circuit was to blame.

The big factor is the ECU is heating up. Hot to the touch...not normal. This by itself says there is a big problem, specifically with the ECU, and combine that with the draw and I think the problem narrowed itself down to the cause.

Luckily, a lot of people are pulling the ECU and harness and replacing their Crossfire stuff in favor of carbs or more modern fuel injection systems. Stay on the search for a new one on Craigslist or Ebay.

I picked up an ECU and harness for $100 for a project, and I know I saw several computers for $50 or so.
 

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I too almost suggested unplugging the ECU to determine if it's the problem or if something else on that circuit was to blame.

The big factor is the ECU is heating up. Hot to the touch...not normal. This by itself says there is a big problem, specifically with the ECU, and combine that with the draw and I think the problem narrowed itself down to the cause.

Luckily, a lot of people are pulling the ECU and harness and replacing their Crossfire stuff in favor of carbs or more modern fuel injection systems. Stay on the search for a new one on Craigslist or Ebay.

I picked up an ECU and harness for $100 for a project, and I know I saw several computers for $50 or so.
D_B
After studying the schematics heres what I have found. The ECM feeds the ECM fuse BPASSMORE is pulling.

BPASSMORE
(The current draw is 2.3 A. with all courtesy lights, accessories and alternator is disconnected. There is no draw with the ECM fuse in the Batt compartment pulled. With the fuse in, the ECM is noticeably warm the next day. Just wondering it that too much pull, the Batt is new and will drain to a no start state in a week.)

So I traced out the circuit and heres what It Feeds.After the ECM fuse power is fed to-

Injector fuses 1 and 2
Pink wire on distributor
Park neutral relay
Pin 3 ignition switch run

I did not go past the ignition switch, if it has failed it could cause a drain staying in the run position.

I do not believe the ECM is bad I think it has a current draw on it feeding these components and causing the ECM to get hot. When he pulls the ECM fuse the current draw goes away and the ECM is feeding power to the ECM fuse.

BPASSMORE I suggest unplugging each one of these components one at a time and checking current draw. If it were me I would look at the base of the steering column and unplug the column connector first. You could have a bad ignition switch. Be sure to keep the ECM fuse plugged in for these tests. If this does not get rid of the current draw try unplugging the other components.:cheers:Mark
 

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Discussion Starter · #12 ·
Mark, the #3 pin on the ign switch feeds both a & b injectors, the ecm, the gauges circuitry, and bu / dir sigs + unfused to dist & park neutral relay circuits. It is dead with key off.
The circuit I am concerned with is the unswitched #340 to the white ecm connector @ pins 10 & 15, it also feeds some fuel pump circuits. The power for it is located in the batt compartment at the junction block. Just checking if we were on the same circuit.
 

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Mark, the #3 pin on the ign switch feeds both a & b injectors, the ecm, the gauges circuitry, and bu / dir sigs + unfused to dist & park neutral relay circuits. It is dead with key off.
The circuit I am concerned with is the unswitched #340 to the white ecm connector @ pins 10 & 15, it also feeds some fuel pump circuits. The power for it is located in the batt compartment at the junction block. Just checking if we were on the same circuit.
No we were not on the same page. I was looking at the ECM fuse in the fuse block. My schematic does not show a fuse in line feeding pins 10 and 15 it shows a direct connection from the battery! So I have to assume either my schematics are not showing all there is to the circuit or protection is built into the ECM. Either way the 12 volt supply is going through the ECM and feeding something else. You may very well have a bad ECM as D_B pointed out or there is a current drain to a component that the ECM feeds through the 12 volt battery supplied through pins 10 and 15. My problem is I do not have the internal circuit of the ECM and am blind to what the 12 volt battery is feeding. If someone else has the ECM schematics they could tell you what pins 10 ,15 supply. This would save you from buying a ECM if it turns out to be something else. Sorry for the confusion :cheers:Mark
 
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