My check engine light does not illuminate after the ignition is turned on, but you can hear the relays click after you turn ignition on, and the rest of the dash lights come on. Also, the motor fusible link has 12 volts. I have a 95 mitsubishi eclipse gs and it has the chrysler 420a engine. It used to work until I bought a new (used) wiring harness and the bolt that keeps the plug in the ecu was stripped so I just got another ecu. We also tucked the wires to the engine harness. It worked fine after we extended the wires, until I went to tape the wires, and then it just stopped working. I also checked some of the wires in some of the circuits, and the harness that bolts in to the ecu on the two power wires that run to the cam and crank sensors, they are supposed to have a 5 volt power from the ecu that is the reference signal, and there is only like 3.something volts on both of the 5 volt reference wires. Also, I used the wire from the old harness and matched up the colors as well, but I only used butt connectors for now. Even though I tried making sure they were really tight ( I even pulled on them to make sure they were tight), I found a few that were loose during the taping, but the check engine still came on just like it was supposed to until I taped the last side that had the wires that ran to the ecu. And I untaped it to make sure there were none that cam loose and there were not. What would cause it to only put put 3 instead of five volts?
Thanks for any help you can give me.

For the CEL, you may just need to replace a bulb in the cluster. I had to do it on my last car(Ford Escort).

Not sure how it is on these cars but I am guessing it would be a PITA.

I wish that was all, I have a scan tool and it can not communicate with the ecu.

Um, good luck :shrug

That is a sign of ECU failure. No communication (with a good scanner not a cheap thing that vatozone uses) and no light lead you to a harness issue or ECU issue.

Start checking all power and grounds at the ECU, if all are good, test continuity between the CEL light pin in the harness of the dash and the ECU pin. Test for appropriet grounds at the ASDL connector. If thats good, find a new ECU.

Originally posted by Star Turbo Talon
That is a sign of ECU failure. No communication (with a good scanner not a cheap thing that vatozone uses) and no light lead you to a harness issue or ECU issue. Start checking all power and grounds at the ECU, if all are good, test continuity between the CEL light pin in the harness of the dash and the ECU pin. Test for appropriet grounds at the ASDL connector. If thats good, find a new ECU.

I just went out and bought a soldering iron and am in the process of soldering all of the previous butt connectors. I have a hunch that this is the problem, as some of them were starting to come loose. I didn't even own a soldering iron before this. I just want to be able to say yes it was that or no it definitely was not.

Terry, I soldered the wires that I needed to, for some reason I think that there is only one black wire with a red stripe that comes in to the ecu. I have a factory service manual from a 97 avenger (my last car) and that shows at least three black and red wires that should be coming in to the ecu. The black wire with the red stripe that runs in to the ecu didn't have any voltage, positive or negative. Anyways, to answer your questions, I did some testing after I got done soldering last night, and although I didn't check all the wires yet, I did check a lot of them. The ASD and Fuel Pump relay both are showing the proper voltages and grounds. The black wire with a white stripe from the ignition switch is showing volts. The red with with the black stripe shows voltage. The three black ground wires are showing a good ground. The red wire with the white stripe was a good ground. This is with the ignition on that I was checking these. When you turn the ignition on, the car dings and then the other dash lights that are not controlled from the computer come on.

Terry or anybody else, Today I changed the little brown plug that is in one of the white connectors under the fusebox, and when I changed that out for the old good one from my old harness it started working, I thought that I had fixed it. Fuel Pressure and everything, even had it running for a few minutes. Later on when I went to start it back up the check engine light did not turn on again. I don't know if I have a short somewhere or what. Because after I had messed with them again, it wouldn't work again. So I have some questions, the black wire with the red stripe at the ecu harness is supposed to be a ground right? Also, Could the plug have a wire loose or could the white plug (under the plastic cover under the fuse box) go bad by itself, I did try tugging on the wires at the white plugs to see if they were loose but to no avail.

According to your sig, your current car is the 95...

The ECU pinouts are different from that, and what you would be looking at in your 97 avenger fsm.

http://www.2gnt.com/index.php?d=1995%20ECU


That black with red is actually supposed to be from the ASD relay.

yeah, you need to use the proper harness diagram but to answer your question, sure harness connectors can be a constant issue. Usea continuity tester on each side of the harness plug with it plugged together to verify. Keep in mind not to turn the car on when your testing and its not a bad idea to disconnect the ECU when checking continuity.

Terry

Ok, will do. And about the pinouts being different, I realize that because the newer cars (like the avenger) had two plugs that go in to the ecu and my 95 only has one big plug. So I only was using the wire colors. But thanks for that link because that will save me from having to buy another one for a 95. While I'm at it, this new multimeter doesn't beep, it just shows numbers for the continuity. The old one that I used to have (it was an auto ranging one) just used to beep if there was continuity, but this one shows numbers so what should I be looking for if there is?

Thanks again fellas, sorry that I'm still a BANME! when it comes to troubleshooting electrical stuff.

Ok, so I think I finally figured out what was wrong that it was working and then wasn't working. I had it running several times tonight. I think what was happening was that when I was going to put the battery terminals on after letting the ecu reset, the positive starter wire was getting snagged on the CAI tube vacuum nipple on the back. So it wasn't actually going on the whole way, causing the everything else to work, but the computer not to come on. After which I would disconnect the battery terminals to let the ecu reset, and when I put them back on it happened again. Since I had it running tonight with the scan tool on the coolant temp reads -40F, the IAT sensor reads -40F, and the MAP sensor is at 2.9. So still a few more bugs to work out. The check engine light is not showing a code for either one though.

If one of those temp sensors fails or you did something crazy with the wiring, the default setting is for them to read -40* just like they are for you. The MAP sensor voltage seems fine if the engine was running. It simply takes a 5v reference signal and modifies it, so it's alright where it is.

Originally posted by XMasta19
If one of those temp sensors fails or you did something crazy with the wiring, the default setting is for them to read -40* just like they are for you. The MAP sensor voltage seems fine if the engine was running. It simply takes a 5v reference signal and modifies it, so it's alright where it is.

The map sensor was when the car was running, I wanted to double check that one, and I will use the book to check the IAT and ECT. I didn't get a chance to do it last night so I will do it when I get done working today. I am just happy that it was running.

yeah, the map sensor voltage would have been lower if the car was off, so it's reading ok. Like I said about the temp sensors, that's their default setting at -40* When the sensor fails, they all ready super cold as a precaution and the vehicle just remains in open loop all the time.

Ok, I changed out the coolant temperature sensor and when I did the coolant temp is still at -40F, and I have the new intake air temp sensor on the way so that is still at -40F, but I don't think that the sensor will fix that because the coolant temp one didn't. Also, I am not getting any CELs for the coolant temp or the iat. And I backprobed the coolant sensor with the ignition on and it was showing 4.87 volts at the harness. So why isn't this working, all of the wires have been soldered now. Is it something with the computer itself?

bump... anybody?