I recently had an issue where I could not get the Informatica PowerCenter Integration Service to start after an install. The service generated this error code: SF_34004. There is an Informatica KB article describing this problem and the appropriate fix:
Basically, it's suggesting that the Integration Service was configured to connect to the PowerCenter repo using the schema credentials and not the domain administrator.
However, I found that this did not help. the repo service was running correctly and the integration service was using the correct credentials. I checked the user running PowerCenter, and realized the INFA_HOME, INFA_DOMAIN_FILE, and other variables were not set correctly. After setting these and restarting PowerCenter, I was able to enable the Integration Service.