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.

Verifies short to ground is not present in spark reference circuit, or an open is not present in ignition jumper harness.
Ignition control module will ground spark reference signal if a window on harmonic balancer is interfacing with 18X Hall Effect switch. Starter may have to be bumped several times to obtain a voltage reading.
Voltage reading should be lower than that obtained with engine not running, indicating a pulsed reference signal.

Fig 1: Code P0321 Schematic (3.8L) Spark Reference Circuit

Fig 2: Code P0321 Diagnostic Flow Chart (3.8L) Spark Reference Circuit