The ECM is grounded to the battery negative terminal at ECM Pin X3-6 and X3-7.
The ECM receives VIGN power at Pin X3-3. The power signals the ECM to provide a ground path from Pin
X3-5 to 85 to switch the ECM main power relay.
Switching the relay provides power from the battery positive terminal through 2 fuses and relay contacts 30 and 87 to Pins X4-1 and X4-2. See truck Chassis Electrical Circuit Diagram Manual for circuit numbers, connector and fuse locations.
Fault Detection / Management
The ECM internally monitors battery voltage. When the ECM continuously receives less than 7 V or more than 23 V, a Diagnostic Trouble Code (DTC) will be set.
ECM PWR Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the flashes from the amber and red ENGINE lamp.
Electrical system voltage B+ out of range high
• DTC 112 is set when the ECM detects an alternator output greater than 23 V at Pin X3–3 for more than 0.5 second.
• DTC 112 can be set when jump starting the engine and additional voltage is introduced.
Incorrect external battery connections can cause the voltage increase.
• If the condition causing DTC 112 is intermittent, the code will change from active to inactive status.
DTC 112 will not illuminate the amber ENGINE lamp.
Electrical system voltage B+ out of range low
• DTC 113 is set when the ECM detects less than 7.0 V at Pin X3–3 for more than 0.5 second.
• DTC 113 can be set by a inoperative alternator or ECM power relay, discharged batteries, or increased resistance in the battery feed circuits.
• If the condition causing DTC 113 is intermittent, the code will change from active to inactive status.
DTC 113 will not illuminate the amber ENGINE lamp.
Unexpected reset fault
• DTC 626 is set when power is interrupted to the ECM. Loose or dirty connections at fuses, relay connections, and battery or ground cables can cause the ECM to power down.
• After circuit becomes intact, the ECM will reboot.
Erratic engine performance can occur. Turning engine ignition switch OFF and then ON will cause the code to change from active to inactive status.
• When DTC 626 is active, monitor the voltage at ECM Pin X4–1 and X4–2. Examine for intermittent connections in the power feed wiring.
The EST can be used to indicate DTCs and display the VIGN voltage measured by the ECM to Pin X3–3.
• DTC 626 will not illuminate the amber ENGINE lamp.
When DTC 112, 113, or 626 is active, see truck Chassis Electrical Circuit Diagram Manual for circuit numbers, connector and fuse locations.
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
• Digital Multimeter (DMM)
• Breakout Box
• Relay Breakout Harness
• Terminal Test Adapter Kit