Failed Smog - No Vacuum pressure to EGR - Code 334
I live in California and my old beat up but beloved 92 Ford Ranger was due for smog. I passed all the emissions testing no problem but I failed on the functional EGR test. The mechanic said the EGR valve was fine, there just wasn't any vacuum being sent to it when he would rev the engine. I checked for trouble codes and found "334 - EGR Closed Valve Voltage High". What parts of the electrical system regulates the vacuum pressure to the EGR? What is the likely culprit here and how would I go about investigating/fixing it? Any and all help is much appreciated. Thanks.