Cold Start Enrichment
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1987 Volkswagen Scirocco, 1987 Volkswagen Quantum, 1987 Volkswagen Jetta, 1987 Volkswagen Golf, and 1987 Volkswagen GTI. However, it is still accessible from the selected car via links, so may be relevant.
Connect test harness between differential pressure regulator and vehicle harness. See Fig 1. Connect multimeter to test harness. Disconnect wiring from coolant temperature sensor. Turn ignition on. Differential pressure regulator current should be 80-110 mA. If not, replace ECU.