Engine Controls - Pin Voltage Charts: Introduction

Pin voltage charts are supplied to reduce diagnostic time. Checking pin voltages at the ECU determines whether it is receiving and transmitting proper voltage signals. Charts may also help determine if ECU harness is open or shorted.

NOTE: Unless stated otherwise in testing procedures, perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance. Voltage readings may vary slightly due to battery condition or charging rate.

ECU circuits are checked at ECU connector with ignition off, with ignition on and engine off, and/or with ignition on and engine running. See Figure -Figure . Test between indicated terminal and a good body ground. When testing pin voltage, carefully backprobe terminal at harness side of ECU connector.
If voltage is not as specified, test and repair or replace circuit or affected component. Retest circuit to verify repair has been made. Unless stated otherwise, perform all tests with ECU harness connected.