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1G ECU not powering on, no 12v at ECU pin 110.

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Jagster

Probationary Member
12
0
Apr 28, 2005
Jacksonville, Florida
Hi folks, I have a '93 Eclipse that I'm working on bringing back to life after siting for 10 years due to a collision that damaged the front end and then later (the car was being periodically started to keep the engine in shape) the car just stopped starting and sat outdoors for a couple years before being towed and stored in my garage. I never thought it would take this long to pick this project back up but sometimes adulting just gets in the way.

Anyhow, I'm now trying to get this car back in running order, the inside is pretty mint, the outside could use a fresh coat of paint and a new left fender. The car was hit right at the drivers side wheel - the fender was damaged a bit and the wheel was pushed way in a the top like it had extreme camber. The car was on loan to my parents when this happened (I lived a couple hundred miles away at the time) and I was not able to address the damage a the time, that is why it sat for so long and eventually towed to me later once I bought a house and could store it with me. The car was "totaled" and the damage seemed like it could require a fair amount of work to the front suspension/steering components (at least to my eye at the time). Since then I've of course gained more knowledge and experience and am now kicking myself for not diving into this sooner because once I got in there to look I couldn't find anything the looked mangled and concluded that possibly it was just the shock absorber that somehow go bent from the impact and after putting in a new shock the wheel is almost back to normal position - it seems it might have just the slightest amount of negative camber now but I'll dig into that if I can get the car running again first. I took the fender off and manually reshaped it back to as close to normal as I could get it, and pulled some of the metal under the fender area to straighten things up there too. Now the body damage looks almost gone but if I get this car running good I'll put a new fender on it.

After fixing the body and suspension issue I went about dealing with the fluids. I drained the oil and gas (this gas tank has a drain plug! :thumb: ), then put fresh full synthetic in there to help clean stuff out. I know the motor has to be pretty dry after sitting so lone so I'm a little worried about that but I pumped oil through using the oil pressure sending unit trick (https://www.dsmtuners.com/threads/priming-oil-pump.286235/#post-151432942) until I saw oil coming out around the rocker arm. I'm not 100% sure this is the best way but that's what I've done so far. If anyone has suggestions on this aspect to prime the motor any better I'm all ears.

So that's the backstory on the car, now to the ECU issue. I decided to check for spark while I had the plugs out (to make turning the engine over easier and let oil distribute a bit on the rings - I placed a little oil in each cylinder) and found I had no spark. I tested resistance on the coils and that seemed pretty normal. I was about to order a new power transistor when I noticed that the CEL was not coming on when cranking the car. Thankfully I came across info on this site on how to diagnose before I just went and bought another ECU (I'm trying to no spend any real money on this until I am comfortable that the car will run an not have any terrible damage to the steering/suspension). Following the instructions, I've found that I don't have any power to pin 110 when the ignition is in the ON or START position. I do have constant power at pin 103 [connector C-59] and MPI relay pin 10, and also get power at fuses 11, 12, & 18 when the IGN is ON or START. After looking at wiring diagrams, it seems that the wire from pin 110 goes up to connector C-54 pin 5. The wire in the electrical schematics is labeled 1.25-BW but I'm not sure what that means really. Upstream it then turns into 2-BW and then 3-BW.

If I have power at fuse 11, 12, & 18 but not at C-59 pin 110 then I would think there is something amiss between C-59 and the ignition connector (C-04 pin 4). And since power is getting to the fuses (11, 12, 18) then it's not at the ignition switch connector itself. Does this all seem reasonable and accurate so far?

I'm having trouble tracking down connector C-54 though. According to this diagram (attached) it's somewhere under the passenger dash but I haven't been able to spot it. Can anyone help point out where exactly I should be looking or if I'm chasing the wrong thing here? Is it behind some HVAC ducting?
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Also, any other tips worth sharing for my endeavor in resurrecting this baby?

Many thanks.
 
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You've actually done a lot of work and research which I commend you for. Its very rare these days, but you are on the right path. ECU pin 110 is switched 12v from the ignition. This is what turns the ECU on and triggers the mpi to power everything up. I.E. coils, pump, sensors..etc

Knowing that, I would start checking for power at the ignition switch then continuity between the switch and ECU pin 110. The labeling usually denotes color code of wire, so in the case of BW, it's a Black/white wire.

Also C-54 I believe is connected to the wall by the kick panel. It should be in the same general area as the harness going through the chassis, to the doors.
 
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Thanks @lasthope05
I'll do a continuity test tomorrow from the ignition to pin 110. I'll post some pictures of the harnesses I see under the dash too, maybe someone can spot or point out C-54 or where it should be (it's a 6 pin connector per the diagram). The harness from the ECU snakes under the carpet towards the firewall and then disappears back there... hard for me to follow it unless I start pulling things more apart and maybe that's what's needed but I don't know.

I figured BW may have stood for Black/White but wire going to pin 110 seems to be just black with brown dashes so I thought it might stand for something else. Any idea what the "1.25", "2", and "3" mean in the equation (1.25-BW, 2-BW, 3-BW) (see attachment). I'm new to reading these wiring diagrams.
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I'm worried by your description of the wire to pin 110 and wonder if you possibly flipped the connector in your mind. The wire to 110 will be black with a white stripe and nothing in the position above it (pin 105 - no BCS on a NT) where the other end has two black wires (pins 101 and 106) both being ground.

You can also look at pin 3 of the ignition coils and pin 3 or the MPI relay for the IG1 signal. If neither of these are present you'll be digging for C-54 again.
 
Excuse the quality, my scanner is down. These are from the 92-94 Eclipse Electrical FSM.
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Thanks for that info @motomattx

Ok, yesterday I tested a bit more with my multimeter but I also found out I was testing pin 106 earlier, not 110 - I was looking at the wrong connector diagram and had the pins reversed. Anyhow, once I figured that out, I retested (with the correct pin 110 this time) and was getting some odd behavior. I had my multimeter set to the audible continuity test setting and when I placed the key in ON, I sometimes got some static sound, like there was just a barely-there connection. (I'm doing the continuity tests with the battery completely disconnected and one of the multimeter leads clipped to the positive battery clamp) When switched to START, the tone went solid. The resistance measurements are crazy too - on START, it's like 4 Ohms or less, on ON it is very high and jumps around 19-50k. I confirmed this by testing right at the connector for the ignition switch itself. So it seems to me that he problem is in the ignition switch, not the wiring harness.

I ordered a new ignition switch (Standard Motor US217) from Amazon and it should be here in a couple days. Hopefully that is all that's needed (and some fresh gas) to start her up.
 
I'm worried by your description of the wire to pin 110 and wonder if you possibly flipped the connector in your mind. The wire to 110 will be black with a white stripe and nothing in the position above it (pin 105 - no BCS on a NT) where the other end has two black wires (pins 101 and 106) both being ground.
You're exactly right, I was reading the pins reversed and testing 106 initially instead of 110. I caught this when performing the continuity tests - I started to question myself if the connector image I was looking at in the manual was harness side or the ECU side. I need to make sure I pay closer attention to that in the future and the color of the cable should've been a huge red flag for me. Thanks for catching my error though and pointing it out, it would've certainly set straight in the event I didn't stumble on my mistake.
 
Ok. Last week I received and installed the new ignition switch. Now I get 12v at pin 110 but still no CEL at the dash. The ignition switch was definitely bad though. I took it apart and it looks pretty simple and visually ok from what I can tell but it definitely has some connectivity issues within it. Perhaps it can be corrected by cleaning up the copper inside a bit but the new switch was less than $10 so it wasn't worth trying to fix the old one.

The relay (Control Relay?) that sits near the ECU clicks very loudly though, so that is the next test for me.
 
Single click on and another after the delay turning off or something else?
Yes, single click when key goes to ON and another when going back to ACC. I tested the relay and everything checked out according to the tests I performed (shown below - Control Relay Inspection).
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The loudness of the clicking is probably normal and just seemed much louder than I remember due to the fact that I have the radio and side panels off which would normally absorb/block a portion of the sound.

I then went back and continued this troubleshooting chain... (I previously only performed #1 and #2 which lead to the discovery of the faulty ignition switch)
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After continuing with #3 and so forth I think I may have found an issue at #4. It says to test for an open-circuit and also a short-circuit earth. I get continuity between 4/5 and 102/107 but I also get continuity to ground from all those pins as well. I'm reading this as that there isn't an open circuit (between 4/5 and 102/107) but there is a short-circuit to ground that shouldn't be there. Is that right? If so I guess the next thing to trace down is where the short circuit is happening... that should be fun OMG

I tested ECU to ground too and that all checked out okay.
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After continuing with #3 and so forth I think I may have found an issue at #4. It says to test for an open-circuit and also a short-circuit earth. I get continuity between 4/5 and 102/107 but I also get continuity to ground from all those pins as well.

I'm reading this as that there isn't an open circuit (between 4/5 and 102/107) but there is a short-circuit to ground that shouldn't be there. Is that right? If so I guess the next thing to trace down is where the short circuit is happening.

If both the ECU and the MPI relay are disconnected while you are performing those steps then you have a problem what would cause the MPI fuse to blow when you turn the ignition on.

Pin 4 and 5 on the MPI relay are the output (switched from pin 10) to the ECU for battery voltage to power the ECU and the rest of the MPI circuit up.

This also runs to quite a bit under the hood (like everything other than the coils, PTM, and fuel pump which are all powered from the Ignition switch). One or more of the other MPI circuit sensors could be shorting to ground.

Did you note the resistance to ground. It might help identifying between a hard short and something like the resistance of the O2 sensor heater.
 
Did you note the resistance to ground. It might help identifying between a hard short and something like the resistance of the O2 sensor heater.

Tested resistance and it was approximately 11.2 ohms (I made video, see below). Is that what should be expected? If so then I guess everything checks out good and I must have a faulty ECU.
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That's not out of wack for the resistance of the heater in the O2 sensor. If you look at the wiring diagram for the NA 2.0L MPI circuit, it's connected to the MPI relay pin 4 and 5 and ground.

Here's an example or just the O2 Sensor Heater
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Have you read my MPI circuit posts?
Lets go back now that you have fixed the ignition switch.

With the ECU disconnected to you have 12+ volts at MPI pin 10 (power from the MPI circuit fuse)?

With the ECU disconnected and the MPI relay connected, do you get 12+volts at MPI pins 4 and 5 when you ground MPI relay pin 8 (Black w/Blue stripe)? How about at ECU pins 102 and 107?

Do you have 12+volts at ECU pin 103 (Red w/Black stripe)?
Do you now get 12+volts at ECU pin 110 (Black w/White stripe) when you turn the ignition switch on?
With the ECU connected does ECU pin 66 (Black w/Blue stripe) go to ground when you turn the ignition on?
If not, does the CEL turn on if you ground ECU pin 66 yourself? (make sure your on the right pin)
 
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