420A No start after trans swap, ground connected to 12V

[Rdawgflex]

I swapped out a bad auto transmission on my 99 eclipse GS with same model trans... i get done and after all that, my dumbass wired the thick starter ground to the positive terminal and Im thinking shorted something right? Because the car started fine before swap. Left it on wired wrong over night. Now Car wont crank over.

However, I see NO blown fuses in the 2 spots and all the accessories are powering on with key forward. Wtf? I replaced the starter with a brand new one now, thinking it was bad but I just hear the clicking, so something's wrong. Battery tested fine, tried a jump anyways, nada.

Im thinking now what if it's the ECU not able to give the command somewhere down the chain? Many thanks for any help, this sucksss , really bummed i did this!

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[miliman13]

Welp if you already checked all your fuses and they are fine then it could possibly be the ECU. I have always been warned about polarity mistakes in these cars, but I have also by accident done it before , briefly and it didn’t damage ECU

Open it and see

 

[Rdawgflex]

Welp if you already checked all your fuses and they are fine then it could possibly be the ECU. I have always been warned about polarity mistakes in these cars, but I have also by accident done it before , briefly and it didn’t damage ECU

Open it and see

Thanks for the input seriously. Yeaa so mine was on wrong, all night. I'm looking for rounded or blown capacitors right?

 

[VelocitàPaola]

The 420A ECU is under a thick slab of potting compound, so there's nothing to inspect or replace there. Does the fuel pump prime with the key in the "on" position? Can you connect a scan tool through the OBDII port? My guess is that the ECU is blown, but I wouldn't buy a new one until I had more evidence.

 

[jesse12345]

So you hooked it up backwards and nothing happened? Maybe you got lucky and the battery was dead? I'd hook it up the right way and make sure you have power going to the starter or does it crank ?

 

[Rdawgflex]

The 420A ECU is under a thick slab of potting compound, so there's nothing to inspect or replace there. Does the fuel pump prime with the key in the "on" position? Can you connect a scan tool through the OBDII port? My guess is that the ECU is blown, but I wouldn't buy a new one until I had more evidence.

So now its weird, the WHOLE power circuit will just shut off if I turn key forward and then there's NO power anywhere until I disconnect and reconnect the battery.

Before, I could at least turn the key and hear the starter solenoid clicking but never able to turn over the engine. I don't hear much of a fuel pump whine but now with the total power circuit going out, I really think the ECU is blown and giving off crazy signals to kill the whole circuit?

Battery tested great. I can't find a single blown fuse anywhere?! eBay has the same part number for just under a 100 bucks which actually isn't too bad..
Anything else I should do to confirm ECU before I pull the trigger on another like-model one?

Thank you very much.

 

[VelocitàPaola]

I'd probably want to see if both the fuel pump and ASD relays are getting power, the various sensors (TPS, crank, cam, etc.) are getting 5-8V, and whether the ECU will communicate via OBDII before deciding it's dead.

 

[Rdawgflex]

I'd probably want to see if both the fuel pump and ASD relays are getting power, the various sensors (TPS, crank, cam, etc.) are getting 5-8V, and whether the ECU will communicate via OBDII before deciding it's dead.

Okay I'm going to reset the circuit to get power going again, then test the fuel pump and ASD relay as well as the sensors with my multi meter to confirm whether the pins are getting power and if not, I'll order a used ECU and try swapping it out..

 

[Rdawgflex]

I'd probably want to see if both the fuel pump and ASD relays are getting power, the various sensors (TPS, crank, cam, etc.) are getting 5-8V, and whether the ECU will communicate via OBDII before deciding it's dead.

Here is my result:

Cam sensor had 9.05 volts, IAC had like 7 or 8 volts, the starter and fuel pump relay both had 12 volts. No check engine lights but i didnt scan since i dont have a scantool on me. Will buy one tomorrow but What is crazy is everything is on until the second i go to turn the key all the way forward then it just kills power to the ENTIRE car's circuit now. This sucks. Could it be the ECU still, doing that to the whole circuit?

 

[VelocitàPaola]

Is it possible the battery just needs to be charged? It sounds like the ECU is doing what it should.

 

[Rdawgflex]

Is it possible the battery just needs to be charged? It sounds like the ECU is doing what it should.

No, I had the battery tested already at parts store and their tester said it was good.

Keep in mind I just swapped the entire transmission to same one, but all my connections look firm and secure. Something must be bad wrong since the whole car is losing its entire circuit power now at full key turn.

Does anyone have any other ideas besides buying a used ECU on eBay right now? I still think its the ECU fried or shorted somewhere and car loses whole circuit when ECU is commanded to turn over motor right at that point BOOM full power shut off. What else could do this BUT the ECU? Nothing I think, I also already tried jumping the car for 15 mins + still same power cut off. Should I try swapping my buddies Honda CRV battery real quick just as a test?

Edit: I did just realize I ran the starter's ground into a strut tower chassis bolt but online calls for it to run to a bolt in the transmission. Could this somehow kill the power at full key turn maybe?

Edit 2: I ALSO noticed the ground terminal connector is very loose on the Battery's ground post. The old tightening nut is rusted/frozen. I'm going to pick up some new battery terminals and swap the old ones out. Just read where even that can cause similar issue..

 

[Brian O Conner]

So with my whole scenario with adding power to the VSS which ended up frying my ECM and it fried the crankshaft positioning sensor. Car did not prime and I wasn't getting any spark. You can change your fuel pump relay and ASD relay cheap but if it isn't that or your crankshaft positioning sensor it probably did fry the ECM.

I even took my ECM apart and there was not any black or burnt spots. Good news is the ECMs for 2GNTs are not very much. Rock Auto has them and AutoZone does as well. Just make sure you get the right one. Also make sure you check all fuses inside car and outside car.

Make sure you scan the car as well with an OBD 2 scanner, because mine would not read any codes what so ever, which is another red flag bad ECM. Ask Velocita, he was replying to my recent posts.

Just remember the lack of burnt spots don't mean anything, mine looked brand new and I definitely fried the ground transistor.

 

[Rdawgflex]

Just remember burnt spots dont mean anything mine looked brand new and I definitely fried the ground transistor.

Thank you for the help.
I'm thinking it has to be the damaged ECU since there's NO blown fuses anywhere, you know?
I'll stop by walmart for an OBD II reader. also going to replace battery terminals with clean ones that I can tighten as the ground one is frozen and is loosely contacting the battery's Ground Post.
Will report back this evening with the results!

 

[Rdawgflex]

Ok so I just checked the voltage on all 3 pins in the ignition coils harness and none had any power whatsoever! Then I checked this sensor thats goes all the way at the end of the Intake Manifold and its connector pins also had no power whatsoever with key off or forward so I think the ECU is bad.

So I just ordered a same year model and same part number used ECU from a high rated eBay parts seller. Should get here next week and I'll swap and pray that the car can crank again. Will update after!

 

[BLACK'98DSM]

Sounds like the ignition switch is alos a possibility.

 

[Rdawgflex]

The new ECU didn't fix it, this sucks! Can anyone help with what else it could be I don't understand because it's getting power, the starter is trying and now I confirmed ALL 3 relays are clicking, and the coil's power harness has voltage right at key turn all the way!

WTF could cause this? I replaced auto trans with known good one but this is stupid, no blown fuses. Battery good. Starter new. The motor doesn't even try to turn over or ignite.

What if the Crank angle sensor is burned out? Wouldn't that cause these symptoms of no cranking/no fuel? I may have seen some smoke come that direction when trying to start it the first time after the reverse polarity mistake.

Edit: What if the new trans torque converter is stuck in park position and thus flywheel crankshaft can't move whatsoever? IDFK guys I'm stumped but its seriously like the motor wont even crank a little PERIOD!

 

[BLACK'98DSM]

A bad crankshaft position sensor would definitely cause no spark and no fuel, however the engine would still turn over. Maybe a wire was melted hence the smoke.

 

[luv2rallye]

Something must be bad wrong since the whole car is losing its entire circuit power now at full key turn.?

Edit: I did just realize I ran the starter's ground into a strut tower chassis bolt but online calls for it to run to a bolt in the transmission... could this somehow kill the power at full key turn maybe??
Edit 2: I ALSO noticed the ground terminal connector is very loose on the Battery's ground Post. The old tightening nut is rusted/frozen. I'm going to pick up some new battery terminals and swap the old ones out. Just read where even that can cause similar issue..

Just saw your post. I'm an electrical engineer and have lots of experience with the DSM electrical systems.

Your symptoms are the classic high resistance (from a poor battery cable connection) causing a large voltage drop across that high resistance spot when a lot of current is trying to flow (the starter current). In your case the problem is most likely the terminal connector on the battery's negative post.

Starters draw at least 50 amps and even a 0.1 ohm resistance (from connections that are dirty, corroded, not clean, not good/enough metal contact, or not tight - OR a crack in the cable itself, or the cable is old or brittle) will drop 5 volts (50 amps x 0.1 ohms = 5v) across that resistance which will not leave enough voltage for the starter to engage/operate. Starters need a steady 9.6 volts minimum while cranking to operate or even engage. So the starter solenoid may click (because it doesn't need that much current/voltage to operate) but the starter can't engage. And yes when this happens (trying to engage the starter), the entire car's circuit power will take a nose dive (which is what you're seeing).

So clean both battery cables/terminals on both ends and tighten securely (remember to clean/tighten the positive post cable end on the starter too - disconnect battery first). And yes the battery negative cable should be connected to (under) a starter bolt head to have minimum resistance.

If that doesn't work, replace the battery cables. Last resort is the starter itself may be bad (although you should pull it out and test it with jumper cables before replacing).

 

[Rdawgflex]

Just saw your post. I'm an electrical engineer and have lots of experience with the DSM electrical systems.

Your symptoms are the classic high resistance (from a poor battery cable connection) causing a large voltage drop across that high resistance spot when a lot of current is trying to flow (the starter current). In your case the problem is most likely the terminal connector on the battery's negative post.

Starters draw at least 50 amps and even a 0.1 ohm resistance (from connections that are dirty, corroded, not clean, not good/enough metal contact, or not tight - OR a crack in the cable itself, or the cable is old or brittle) will drop 5 volts (50 amps x 0.1 ohms = 5v) across that resistance which will not leave enough voltage for the starter to engage/operate. Starters need a steady 9.6 volts minimum while cranking to operate or even engage. So the starter solenoid may click (because it doesn't need that much current/voltage to operate) but the starter can't engage. And yes when this happens (trying to engage the starter), the entire car's circuit power will take a nose dive (which is what you're seeing).

So clean both battery cables/terminals on both ends and tighten securely (remember to clean/tighten the positive post cable end on the starter too - disconnect battery first). And yes the battery negative cable should be connected to (under) a starter bolt head to have minimum resistance.

If that doesn't work, replace the battery cables. Last resort is the starter itself may be bad (although you should pull it out and test it with jumper cables before replacing).

Thank you so much for the response. Very helpful to know, I also think this is a current/electric issue happening here.
However, update: New starter (either one same symptom though) so it should be good. New battery and clean. New ECU. (Either one, same symptom though).
The thick black/yellow ground wire is now going to the upper starter bolt and that seemed to improve the current a little but still NO actual cranking whatsoever. I replaced ground terminal with brand new and stripped it back some to cleaner wire. STILL no cranking. The positive terminal looks fine and again, the car had NO problems cranking before the trans swap and my accidentally reversing polarities. I cant find any melted/broken wires, no blown fuses BUT check this! Below is a picture of these 2 relays right behind the stereo. Isnt the left one the STARTER relay?! I think on turbo cars it is at least. Where is mine?? Anyways, I feel NO click or movement in this relay whatsoever when my buddy turns the key... pic attached. What if this burned out and thats why nothing is working to make ANY starter crank my motor?
Pics:

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[VelocitàPaola]

Below is a picture of these 2 relays right behind the stereo. Isnt the left one the STARTER relay?! I think on turbo cars it is at least. Where is mine?? Anyways, I feel NO click or movement in this relay whatsoever when my buddy turns the key... pic attached. What if this burned out and thats why nothing is working to make ANY starter crank my motor?

I believe the left relay is the door lock power relay, and the right is the starter relay.

 

[luv2rallye]

The left one is the starter relay and right is door lock. I have the real 1999 Mitsubishi Service Manual and they have it labeled backwards (so probably all other manuals then do too).

 

[VelocitàPaola]

The left one is the starter relay and right is door lock. I have the real 1999 Mitsubishi Service Manual and they have it labeled backwards (so probably all other manuals then do too).

Ah, okay, that's what I was referencing: the 1997-1999 FSM.

 

[Rdawgflex]

Guys I think I finally found the culprit. I Just tested both the old and new starter and both are getting the proper 12 volts and trying to crank.

So I thought to try hand cranking the motor with a wrench on a cam sprocket again and what do you know the whole motor is like locked up, will not budge whatsoever. This is in neutral or park.
I replaced the auto trans with same model and while i was mating the TC to the flywheel, I was always able to crank it where i needed. Once I finished all 4 mating bolts, I simply bolted the bell housing to the motor, mounted it back to the chassis, filled it with ATF while checking the level and everything.

Actually now I think I even found the culprit for the hard stop of the crank.. I think somehow the little short mating bolt's heads are making contact with a lip of either the bell housing or the metal dust cover or something like that.. so I'm going to bend the dust cover back/straighten it and see if the flywheel is unobstructed and we have lift off again. I may have bent up that metal dust cover whilst removing/adding the new trans... oops. Will Report back.. Thank you all.

 

[BLACK'98DSM]

Please do not attempt to rotate the internal assembly via the camshaft sprockets bolts. That's a great way to jump timing. The hydraulic tensioners are known to lose pressure over time. For future reference, it's best to rotate the crankshaft pulley bolt.

 

[Rdawgflex]

Please do not attempt to rotate the internal assembly via the camshaft sprockets bolts. That's a great way to jump timing. The hydraulic tensioners are known to lose pressure over time. For future reference, it's best to rotate the crankshaft pulley bolt.

Thank you for the correction, noted big time. Will update soon..