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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8612
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Mitsubishi Eclipse Spyder GS: The problem is that the ECU unit

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The problem is that the ECU unit is only firing 2 cylinder, the mechanic says I need to get a new ECU unit(MR578508).I was able to find a used one on but only getting the ECU unit, no Key Immobilizers .I wanted to know if it Will work with my old Key Immobilizer. Also if will there be any problem if a buy a ECU that has same code MR578508 but its from a Coupe version?

Thanks for your patience.

If you are experiencing two cylinders not firing, moving the coil back and forth does not change which cylinders fire, and your primary checks have already been done verifying the belt timing is correct and the cam and crank sensors are working properly (we sometimes see aftermarket cam sensors cause this problem), then your mechanic is dead on, you will need M578508, barring any unusual wiring damage. I would only be cautious if this is a problem that developed after the harness was replaced, as you would then want to evaluate the odds of it being something caused during the repair.

On this model you do not need to replace the immobilizer ecu.... only 2000 and early 2001 models required this, 2002 models and later you can re-use the immobilizer ecu and only replace the bad engine ECU.
However, you will need to have the keys re-programmed after the new ECU is installed. This is because the immobilizer information is actually stored in the engine ECU. The immobilizer ecu is used to traslate the information, but the engine ECU is used to store it, so when you replace it you will lose your key information.
Any dealer can program your keys for about $45 once the ECU is installed.

ANy MR589508 ECU will work, but it MUST be that number.... it can not be a different number but from another 2002, etc. The number must be exact.

Again just to be clear, the ECU can be replaced without replacing the immobilizer on your 2002, but you will need to have the keys reprogrammed afterward.
Doug and other Mitsubishi Specialists are ready to help you
Customer: replied 4 years ago.

Hi Doug,


Thanks for the reply it really helped me. So based on my understanding its gonna be this way : I will buy a used ECU(MR578508) and give it to my mechanic directly (ie without reprogramming/flashing ECU unit). Then get the Keys reprogrammed.


So would he (mechanic) be able to start the car ? I mean to say that if its the same ECU(MR578508) I dont have to get it reprogrammed ?


You will get the new/used ECU with the same part number, he can install it in the vehicle. Further, he can then verify if spark is restored without programming the key in case there is any doubt there.
The immobilizer system only disables the fuel injector pulse.... nothing else. So since you are trying to restore spark to one of the coil packs, you can plug the ECU in and check spark to see if it is resolved. If it isn't, his diagnosis is incorrect (and look to wiring issues or cam belt/sensor issues). If the spark is restored, then he will have the vehicle towed to a dealer to have the key programmed.

Because the immobilizer turns off the injectors if the key isn't programmed, the engine will not run until the key is programmed. You will be able to run it on starting fluid however, as everything but the injectors will work.

Again to be clear, you do not need to do any other programming besides the key to the new ECU. You can verify the spark without programming the key (so if the problem is the same you can put your old one back in and not worry about having to program keys).

If you have any questions please just let me know.
Customer: replied 4 years ago.

So from this I understood that the mechanic will only have one chance to see if the spark has been restored and if the ecu is working coz in the next turn it wont have the starting fluid to start the engine. Then he has to get the key reprogrammed.


If the spark has not been restored it means that there is some other issue.


Sorry for the delay, I had left for the night by the time you posted.
No you will be able to check for spark indefinitely, just pull a spark plug lead and plug out and ground the plug on the engine.... in this condition you will be able to see if it sparks whenever you crank the engine; it does not need to "run" to check spark.
On the other hand, yes you can just feed it starting fluid to see if spark is restored too if it runs smoothly like all cylinders are firing.

Pulling a plug and checking the old fashioned way is the thorough way to do it though.
If the spark is not restored on all cylinders with the new ecu, there is a different problem and it was diagnosed incorrectly.... at that point there is no point in getting the key programmed as you can put the old ecu back in for further testing.
Customer: replied 4 years ago.

HI Doug,


Sorry for the late reply, my car is working with the new used ECU but the service engine light is on and the car is vibrating a lot. what you think the reason is? Also in the process of replacing the wiring harness they broke my dashboard cover, can you tell me if 2002's MITSU Eclipse spyder GS dashboard can be replaced by 2003's ?


I will close this question after this.




It's no problem, I am here as long as you need.

With regard to the Service Engine Soon light being on, you will need to get the codes scanned to see what is going on there.... with about a hundred different possibilities to turn the light on it would be more than a bit difficult to speculate accurately at the cause without the code(s). Most auto parts stores (outside of California) will check the code(s) for you at no charge.
The vibrating is a tough call, as it may be related to the Service light (if it is a misfire, etc) or could be completely unrelated (worn motor mount, very common on this model).

The dashboard cover you can use any Eclipse/Spyder dash from 2000-2005. While they changed in small amounts, nothing that would prevent use (some had blue inserts, etc). This dash boards are really fragile nowadays though, so the odds of finding a good used one are not that great (and if you do it may break on removal). To make matters worse, a new one is ridiculous money (pushing near $1000 last I checked).

You can get "repair kits" in the aftermarket for this dash though which may be the way to go if yours is just broken on the top etc and not major structural. The repair kit is a molded "duplicate" of the original dash top panel that you glue over the remaining parts to give the appearance of an intact dash. I have seen two of these in action and they look good.... if I didn't work on them daily I probably wouldn't have known the difference.
Here is an example
Customer: replied 4 years ago.

Hi Doug,


I have had a got a few parts from junkyard but couldn't find the Dashboard.


I am not worried about that coz there is major issue again. The car is overheating , after replacing the ECU I drove it for at least 50 miles and it ran fine without any problem. But this one day I was at a signal and then all of a sudden I saw smoke coming out of the bonnet and inside the car(the smoke was white). The indicator was at the maximum level heat. I thought that this is happening bcoz there is no coolant in the car and I filled it up,but even after that it did the same thing. I stopped the car few times in between to cool the engine down and reached home.


I dont know what is it this time? Is it a ECU problem or wiring harness problem or thermostat ? The smoke was coming from behind the engine. Can you suggest me what problem it might be and how expensive this is gonna be?





This certainly doesn't sound good....
You say there was white smoke under bonnet and inside... I assume you had the fresh air turned on allowing the smoke inside via the AC system.
Are you able to see any moisture in the engine compartment after it cools? Often the coolant will leave a residue (often white or light green) where it has sprayed and dried.

If we can narrow down a bit the area of origin we can decide where we need to look to verify the problem then make an estimate.

Customer: replied 4 years ago.

The smoke was coming inside the car from the broken parts of dashboard , the A/C system was off completely. I didn't see any residue on the visible parts but it did had a little moisture when I switched off the engine.


I am sure that the smoke was coming from beneath and behind the car engine. Everything was fine around the radiator area , I didnt see any smoke in that area. Also I don't know if this will help but after all the repair the A/C system has stopped working properly, the heater is working fine but doesn't cool the air.







Thanks. I should have been more clear with regard to the fresh air..... if the Recirc button (picture of a loop opposite the rear defogger button) is off the system is on fresh air.... even with the system turned off this will allow engine air to enter the interior via the grill below the wipers.
Most people leave it on fresh air, and I would suspect this is the case here (you can check to see if the light on the button is on or off if you want).
At any rate, this would allow smoking from the engine bay to enter the dash ductwork.

You mentioned the smoke seemed be coming from the firewall side of the engine; are you able to see any splatter stains around there? There are several things relevant in this area, including heater hoses, a water pump cross over pipe, throttle pre heat hoses, etc.

With regard to the AC being inoperative... I can't think of any relevant reason why changing the ECU would cause the AC to cut off that could have happened during ECU replacement. If the new ECU had a bad ground driver for the AC pressure switch circuit that would cause it of course... it would be the very first time I had heard of that happening though. More likely it is just bad timing and you will need to diagnose the AC system separately once the over heating and coolant leaking problem is resolved.
Customer: replied 4 years ago.

One more thing came to my mind after reading your reply that there was a sound like something is getting boiled ( like water or some liquid) whenever it gets over heated. Then it started giving out the smoke.


I didn't see any splatter stains coz it was from underneath the Engine where thermostat & wiring harness is placed.


With regard to the boiling sound.... do you hear this sound even after just 5 minutes of running (while the system still seems cool/warm but not hot)?
I'm going to need to excuse myself for about an hour, but I will get back with you as soon as I return to work. I don't want you to think I am ignoring you.
Customer: replied 4 years ago.


Only when it reaches to HOT level.


Take your time Doug.



Thanks for your patience; I had an emergency here that I needed to tend to.

Okay so the bubbling that you hear likely is boiling if it is only occurring when very hot. Do you have any smoke from the exhaust (significant, heavy smoke that is)?
When you run the vehicle up to temperature and beyond, are both radiator hoses very hot, or just one?
When you add coolant to the vehicle, so you see it dripping/running out anywhere while the engine is running?
Customer: replied 4 years ago.

Hi Doug,


The exhaust is normal , no smoke at all. Yes the radiator hoses gets very hot. Yesterday I filled the whole radiator and reservoir tank with coolant while the engine was running. I saw there was a very little smoke from the radiator when it was full with coolant, I thought the radiator fans would turn up automatically if its getting heated up, I waited to see if they will turn on automatically but it didn't (may be its some connection problem ). Then I drove for 5-6 miles, it ran fine without over heating. I think has something to with the A/C connection and thermostat.

Finally I dropped it at a Mitsubishi dealer for repair. Also what you suggest me on should I keep this car or get rid of it? Its doesn't have many miles on it (80k approx).




That is a bit odd, perhaps you just have a fan problem. If you turn your AC on, does the radiator fan come on then?

With regard to keep or sell, what are your long term plans with a vehicle? Do you see yourself in it say 5 years from now?