Fueling issues

[Hadi]

Hi

Strange problem happen to me yesterday, actually it's first time I saw this happen.
In the past we did many K swaps for eg and ek civics.

But yesterday after starting tuning the car, I noticed that when the cooling fan is on the car goes too rich, the short trim fuel trim goes fully negative (default -27%).

We checked all parameters carefully, Don't know what causing this ?
The car 750cc high impedance injectors.
Other than that the car is running perfect.

Any one faced this problem before ? Any ideas ?

Regards

[Hondata]

When the cooling fan comes on the ECU is grounding one side of the fan. If there is a poor ground then the ECU ground voltage rises, and this makes the ECU run erratically. If could also be a wiring short.