Ground Circuits

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

Using DVOM, check for continuity to ground at PCM ground terminals. For connector terminal identification, see Fig 1 -Fig 4 . To identify circuits, see WIRING DIAGRAMS . Resistance should be less than 5 ohms. If resistance is not less than 5 ohms, repair open in ground circuit.
Connect negative lead of DVOM to a known-good ground. Backprobe positive lead of voltmeter to each PCM ground terminal. With vehicle running, DVOM should indicate less than one volt. If DVOM reading is greater than one volt, check for short to voltage, corrosion or loose connection in ground circuit.

Fig 1: Identifying Power Control Module Connector C1 Terminals

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Fig 2: Identifying Powertrain Control Module Connector C2 Terminals

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Fig 3: Identifying Powertrain Control Module Connector C3 Terminals

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Fig 4: Identifying Powertrain Control Module Connector C4 Terminals

Courtesy of GENERAL MOTORS CORP.