I just looked at the dash of my 89 G20. When the key is turned to on, not all the way to start the engine, the Servce Engine Soon indicator message appears below the odometer area, the larger cluster on the left. In the same little area is the handbrake light, to the left of the Servce light, and th seatbelt light t the right of the Service light. My van is a bare bones stock G20, so not sure if a custom conv van has a different cluster. That's why I couldn't pass CA smog. The tech turned the key and the Service Eng Soon indicator wasn't showing. It should be on and appear prior to start and then disappear. Therefore, had to troubleshoot and found the brain computer was off. Or a mouse ate your wires !!