Control Module Power & Grounds, & Component Power & Grounds

Poor power or ground connections can cause widely varying symptoms.

• Test all control module power circuits. Many vehicles have multiple circuits supplying power to the control module. Other components in the system may have separate power circuits that may also need to be tested. Inspect connections at the module or component connectors, fuses, and any intermediate connections between the power source and the module or component. A test light or a DMM may indicate that voltage is present, but neither tests the ability of a circuit to carry sufficient current. Ensure that circuit can carry current necessary to operate the component. See appropriate WIRING DIAGRAMS article.
• Test all control module ground and system ground circuits. The control module may have multiple ground circuits. Other components in the system may have separate grounds that may also need to be tested. Inspect grounds for clean and tight connections at the grounding point. Inspect connections at component and in splice packs, where applicable. Ensure that circuit can carry current necessary to operate the component. See appropriate WIRING DIAGRAMS article.