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Test Description

WARNING: This page is about a different car, the 1995 Oldsmobile Ninety-Eight and 1995 Buick Park Avenue. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Test numbers refer to numbers on diagnostic chart.
  1. If QDM related code is stored, diagnose that code first. Repair made to related code will repair Code P1640 also.
  2. If QDM No. 1 symptoms are present, checks on Code P1640 (2 Of 2) chart should isolate cause of fault.
  3. This test will determine which circuit is out of specification.
  4. Determines if problem is circuit or component.
  5. As factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.
Fig 1: Code P1640 Schematic (3.8L) QDM No. 1 Circuit
G95C13906
Fig 2: Code P1640 Diagnostic Flow Chart (3.8L) QDM No. 1 Circuit
G95A13888
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