Where is the ecu for a 90 Chevy s10 2.5l?

The ECU (Engine Control Unit) location on a 1990 Chevy S10 with a 2.5L engine is typically under the dash, on the passenger side. However, it's not always in the exact same spot, and could be slightly different depending on options and trim level. You'll likely find it near the passenger side kick panel, possibly under a cover. It's usually a black box with multiple connectors.