Code 4-3-1 (EGR Temperature Sensor Absent/Faulty)
WARNING: This page is about a different car, the 1994 Volvo 960. However, it is still accessible from the selected car via links, so may be relevant.
Measure resistance between terminals No. 14 (Black wire) and No. 22 (Yellow/Black wire). Resistance should be 500-1000 ohms. If resistance is not 500-1000 ohms, check wiring, connectors and ground terminal on intake manifold.