Transmission oil in ECU - Vitz 2007

[ChathurangaW]

Car has been having rough idling. Mileage is 107K, but seems not the actual. Suddenly acelleration was not properly working and the car was moving very slow in D. I took the car to a mechanic. One plug was like burnt. Wiring was checked.

In the same time ECU was inspected by him and it was full of transmission oil.

I have no clue about it. Does it has an effect for the above failures?

[iRage]

4 hours ago, ChathurangaW said:

Car has been having rough idling. Mileage is 107K, but seems not the actual. Suddenly acelleration was not properly working and the car was moving very slow in D. I took the car to a mechanic. One plug was like burnt. Wiring was checked.

In the same time ECU was inspected by him and it was full of transmission oil.

I have no clue about it. Does it has an effect for the above failures?

The rough idle, etc..can be because the plugs were spoilt. So now you need to figure out why the plugs got spoilt (assuming there were no oil leaks on to the plugs or anything). Were there any shorts in the cable and the connections are all good ? Distributor not having any issues ?

The ECU is sealed pretty well so having oil on the ECU body is not going to spoil it. If the oil gets in to the connector though is a problem. If the ECU seal s are broken then that could also cause the ECU to spoil. 

[ChathurangaW]

On 1/6/2021 at 6:19 PM, iRage said:

The rough idle, etc..can be because the plugs were spoilt. So now you need to figure out why the plugs got spoilt (assuming there were no oil leaks on to the plugs or anything). Were there any shorts in the cable and the connections are all good ? Distributor not having any issues ?

The ECU is sealed pretty well so having oil on the ECU body is not going to spoil it. If the oil gets in to the connector though is a problem. If the ECU seal s are broken then that could also cause the ECU to spoil. 

Is there any purpose of filling oil into ECU? (Actually oil was inside the ECU)

Edited January 19, 2021 by ChathurangaW

[Davy]

I have a feeling that these two issues are unrelated. Your car was probably struggling to idle and move because one of the cylinders were not firing due to the defective spark plug (I assume you were referring to spark plug when you said that one plug was burnt). So you should get that issue sorted out first. Replace all spark plugs for starters and ensure they are gapped properly. If you get the genuine Toyota spark plugs for the Yaris, they should be gapped properly from the factory.

Automatic transmission fluid is non-conductive. So even if you submerge the entire ECU in ATF, it'll probably not cause any issue to the functions of the ECU. However, if ATF got into the ECU, then pretty much any other liquid (or even other contaminants) could have gotten into it which could damage it. So I suggest getting the ignition circuit tested at the agent if possible. The ECU should be thoroughly cleaned with contact cleaner and carefully re-assembled, making sure it's not compromised. Also, get the transmission oil leak fixed ASAP. 

The 4 pin ignition coils that come on these Toyotas are pretty robust. They also feed-in a signal back to the PCM to throw an error code (P1305) if any of them fail to fire. So if you don't have a check engine light, I think it's safe to assume that the ECU is still okay. But getting it tested is just so that any doubt is eliminated.