Whenever the coolant fan is running on my 1993 C4, the check engine light comes on. The light eventually will turn off when the coolant fan is turned off. I scanned it and the codes were 44 & 64 (both codes reflect engine running to lean).
I replaced the oxygen sensor and the MAP sensor, and the light still come on. Could it be the coolant temperature sensor? I don't know. I am running out of options. If anyone has ran into this particular problem?

recently my Escalade had this problem found fuel pump pressure was low 47 instead of 53+ caused lean error

|UPDATED|6/29/2016 9:19:55 AM (AZT)|/UPDATED|

I never had this problem but based on the codes, I would check the fuel pressure as previously stated and check for vacuum leaks.

This ia a follow up on my original post. Thanks for the replies I gotten. The check engine light only comes on when the cooling fans comes on. I flashed the codes again, and they came up the same-codes 44 & 64. And, there were two new codes as well-55 & 63. Code 55 is engine running lean, but code 63 in the Chilton manual says that it can be a faulty ECM or ECM ground circuit. So, with that being said, the problem is the ECM. I already ordered the ECM from Rock Auto. I will keep you guys updated on what the outcome is. Thanks.