Diagnostic Procedures (Grand Prix, Impala, Monte Carlo & Park Avenue)

Fig 1: DTC P1639: 5-Volt Reference Circuit "B" Or No. 2 (Steps 1-5)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC P1639: 5-Volt Reference Circuit "B" Or No. 2 (Steps 6-10)

Courtesy of GENERAL MOTORS CORP.