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2g 420a no start after new harness

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TimF

10+ Year Contributor
823
5
Mar 14, 2011
Aurora, Illinois
So I bought a turbo 420a with a built motor at the begging of the year. At the time of purchase it only needed a clutch but still started and drove. After replacing the clutch the car would no longer turn over and if it did it would instantly die again. I was told that the haltec ecu that was in it ( a older model) lost its tune,so I attempted to download the software which would not work on my laptop. So at that point I sold it for a few hundred, and purchased a stock ecu (out of a manual trans car) stock engine harness (pulled out of a 97 auto in the junkyard, which is all they had. my car is also a 97) and stock injectors with the intent of getting the car running on stock conditions. After getting the harness, ecu, ect all in and connected the car will not crank. The starter is tested and working, and if I connect the starter directly to the battery the car will crank, but will not when turning the key. The ecu seems to not be powering up, because if I connect my scanner/code reader with the ignition turned it says no connection. And the fuel pump is not working via adj fpr with gauge ( no pressure built). All other electronics in the car work, fans, headlights, wipers, dash lights (except CEL). Battery is brand new. I am horrible with electronics and diagnosing so if anyone can help point me in the right direction.
 
The haltech should have been wired to control the fuel pump relay. where were the power wires from the haltech connected to? The ignition switch? battery? Or was it using the wiring going to the stock ECU.
I gotta do a brake job right now but when im done ill post up some diagrams and shlt
 
EDIT: i just noticed you didin't say what year the car was you got the ecu from. 97-99 Ecu should all work, i know 95-96 won't work because they are pinned slightly different.


==============================================
first thing, have you checked all fuses, fusible links in the both the interior and underhood fuse boxes? if they are all good, next check power and ground to the ECU/PCM.

97 electrical manual
howtoread_circuit_diagrams
--------------

[A-106] Top plug on ecu
[A-107] Bottom plug on ecu
-----
check that you have continuity between
(-)ground --- [A-106] PIN10 (black)
(-)ground --- [A-107] PIN50 (black)
(-)ground --- [A-107] PIN47 (black)

------
check for battery voltage at:

[A-107] PIN46 (red/black)
this is the battery back up to the ecu so as long as the battery is connected it should have power going to it.
------
with the ignition switch in the on position, check for battery voltage at:
[A-106] PIN20 (black/white)

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The haltec was originally just a combination of the original harness cut up, and a fee extra wires for additional sensors like a omipower map, gm iat, 1g cas, etc (yes a 420a had a 1g cas on it) I looked at all the fuses in the box and none seem popped. And I read that the 95\96 is different but so are the plugs so they won't work with the harness.
 
i just looked it up, the 97 has the same plug as the 98-99 but it is pinned different.
do you know if the ecu you have is from a 98 or 99?
 
I asked the guy I bought it off of. I googled the part number for the ecu and it says its from a 97,98,99 eclipse 420a automatic. But the former owner said he is 100% it came out of a 5 speed car
 
97 420a ecu pinouts
98 420a ecu pinouts
an AT ECU works on a MT , you just have a check engine light on constantly and the rev limit is 500 or 600 rpms lower. i drove my MT 98 RS for like 6 months with an ECU out of a 99 AT.

the pins on a 97 are diffferent. take a look at this, its the first page of the 97 pinouts next to 98 pinouts.
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That's odd unfortunately when I looked online the part number said it was 97-99 for that ecu. So now I am insure if I have a 97 or a 98 ecu. The seller said it was a 97 but he also said it was a manual ecu to. Unfortunately I can't find anyone in my area that can help
 
well the power and ground wires to the ecu are the same for 97-99 so you can still check for power to the ecu. the different pins between the 97 and 98 doesn't really make sense cause the part# are the same. I have the 98 FSM in print and a pdf copy of the 97 FSM, so i compared the pinout list to them. They are correct but the main difference that would keep the car from starting is the wire for the 1/3 coil on the coil pack. i don't think it would keep it form turning over.

if you haven't already check for power to the ecu.

does your car have the anit-theft system?
how does the wiring look under the column cover, like is there wires that were/are spliced into the ignition switch harness?
any relays under the dash that look like they have been added?

not that it would keep your car from starting, but what did you do for the vehicle speed sensor since the automatic harness doesn't have the plug?
 
I didn't loOK under the column at all no, and as far as I know it has no anti theft. All manual locks and manual window. The only extra relays are in the engine bay. The stock ones where also still there and I plugged into those. There was also a relay behind the stereo that the auto harness would not fit into but I grab the one that came with it and kept that plugged in as well. I'll try and check tomorrow but to be honest in not to sure how. Electronics is not my Forte I am just good with wrenches and bolts.
 
If your talking about the starter relay, they are different, im not sure if it will work with just using the AT starter relay. i look into it

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here is the diagrams for the starting circuit.

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Yes that's the one I just kept the one that came with my harness
 
with the AT harness and starter relay, it wont turn over because the relay is activated by the transaxle range switch. you don't have that , its only on an AT.
 
if you take the (black/yellow) wire on PIN3 of the starter relay and splice it into the (green/black) wire on the clutch pedal sensor, it should work. there are 2 (black/yellow) wires on the starter relay, a skinny wire and a fat wire. The one you want is the smaller of the 2

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if you take the (black/yellow) wire on PIN3 of the starter relay and splice it into the (green/black) wire on the clutch pedal sensor, it should work. there are 2 (black/yellow) wires on the starter relay, a skinny wire and a fat wire. The one you want is the smaller of the 2

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Would that matter if the clutch pedal sensor doesn't work. It's disconnected

I just checked. The switch is gone Completly

And other than checking using my code reader how do I see if the ecu is getting power
 
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You can just take the wire at PIN3 on the starter relay and ground it. Cut it and on the end still attached to the relay plug, ground it to the chassis.

Do you have a test light or multimeter?
 
Sorry I been a way for a while. Work has been throwingout mandatory ot at me like crazy. So up date. I grounded out that relay like you said. Car now cranks. I also fallowed a 97 pin out. Turns out the harness I had was wrong and from a 98. Got a 98 ecu. Now the car is communicating with the ecu. The cel comes on when I turn on power and my code reader will read the car. Currently I have p1495. The car still won't turn over just crank but it seems like I am getting no fuel pressure
 
OK checked and my fuel pump just needed to be plugged in. I still have 1495 and now have 0340. Still no start

I also noticed that my tachometer is not reading rpms. Should still bump up when cranking I believe. The car cranks healthy. Starting to think ts a ignition issue
 
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p0340 is for the cam sensor. you may wanna double check that its plugged in correctly, cause on the harness the cam sensor, ignition coil, and VSS all have the same plug. the cam sensor plug and the igniton coil plug are grouped together but the ignition coil plug has gray sheathing on the wires leading up to it. the VSS plug is grouped with the TPS and IAC motor plugs.
if everything is plugged in correctly, it could be the sensor. i would stay away from autozone sensors since i have seen new ones that dont work.
you can also unplug the sensor and see if the car fires. if it does the dowel pin for the cam gear is probably broken off.
 
The sensor I got was just pulled of a junkyard car kind of dirty and crappy looking but they didn't even charge me for it. The car believe it or not was on a 1g Cas when I got it
 
thats some crazy sh!t. Its probably because the haltec was able to read the signal from the 4g sensor but not the 420a sensor. But how the
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would that even bolt up.

did you make sure that the magnet is still on the end of the camshaft? the 1g CAS is rotated by a slot in the end of the cam so to get it to work on a 420a, i would think the magnet would need to be removed from the cam.
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They had a custom made adaptor I'll see if I can find it LOL. Yes when I grabbed the Cas I also grabbed the magnetic part that goes into the cam. I needed that because part of the 1g Cas adaptor was in its place. So it does have that part. I actually went out and checked the wires I had the right plug. I unplugged it and replugged it and now my car is reading rpms and it seems like it wants to start put just back fires now. So at least it has spark
 
OK now I ordered a brand new cam sensor. Still won't start or read. Wiring issue I am assuming now
 
when you say it won't read, do you mean your scanner won't read?
if thats what you mean try the key dance and see if you get any codes.

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scan tool gets power from dedicated fuse 11 (engine bay fusebox),

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