Pcm Power & Grounds

Poor power or ground connections can cause widely varying symptoms.

• Check 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. Check 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 Digital Multimeter (DMM) may indicate that voltage is present, but neither tests the ability of a circuit to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the component. See POWER DISTRIBUTION in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
• Check 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. Check grounds for clean and tight connections at the grounding point. Check the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component. See GROUND DISTRIBUTION in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.