Control Pressure Regulator

Check control pressure regulator (cold and warm). If not to specifications, replace regulator.
Disconnect electrical plug from air flow sensor and the positive wire from alternator. Install pressure gauge and set valve to open. Turn ignition ON without starting engine.
Disconnect electrical plug from control pressure regulator and measure voltage at plug. If none, check power relay and pump relay. If voltage is available at pump relay, problem lies with wire connecting control pressure regulator and pump relay.
If voltage is reaching regulator plug, check resistance across regulator terminals for 20 ohms. If resistance varies greatly, replace control pressure regulator.