420A 1997 Eclipse GS (n/t)

[airtime37]

I have a 97 GS that got a hole in the oil pan and spun rod bearings.

Tried replacing them hoping for the best but the motor blew shortly after. So I bought a junkyard motor that was tested and ran. I put it in my car and wouldn't start. Had a trained mechanic friend of mine look at it and he says the ECU is blown. And he found the plug for the coils switched with the speed sensor.

Would those plugs being switched cause the ECU to go out? Or is there a different cause of ECU going bad

 

[WES_393]

Have you tried starting the car after fixing the wiring issue? If not, that would be my next step. Having those two crossed would definitely keep the car from starting so it's possible the ECU isn't even damaged. If the car still won't start after fixing the wiring, try swapping in an ECU that is known to work and see if it fixes the problem.

Also, the most common mistakes that I've seen damage an ECU are missing grounds (such as leaving the negative battery cable unhooked) or accidentally switching power and ground (such as hooking up a battery or jumper cables backwards). However, it's my understanding that the 420a ECU is nearly impossible to inspect visually. So like I mentioned, if you suspect that it's damaged just swap in an ECU that is known to work.

 

[airtime37]

Yes he did try to start it after switching the plugs bbut got nothing. He said he was checking the Ecu with a multimeter and wasn't getting any of the right readings out of any of the wires coming out of the Ecu he the book that says what volts should be coming an different pins and nothing was coming out right. He says it's definitely blown

My question mainly is could switching those wires cause a short in the Ecu

 

[trboeclpse98]

Does your car look like it has two ECU's? or just one? That year some came with an ECU and TCU (Transmission Control Unit)

 

[jayson427]

only automatics have tcu's and having those two sensors switched around would not have caused your ecu to go out. what year was the motor that you got from the junkyard, was it an auto or 5speed car and what tranny do you have in your car now? if you missed any ground wires the ecu wont get the correct power. you need to check if you have power to your asd relay on the firewall by the master cylinder. if the motor was out of a different year then that will make a difference. you should have bought the ecu with the junkyard motor. double check all your wires on the engine harness.

 

[airtime37]

When I ordered it they told me it was out of the same year as my car. (1997) is there some way to check the motor and see? And I believe it had a manual trans attached b4 and I have a manual trans in my car.. I ordered a new ecu.. My mechanic has a wiring diagram and went over everything and the only thing he found wrong was those two sensors. But he thinks maybe one of the grounds wasn't fully tight.