How to fix EEC Voltage Low on Detroit engine?

Figure 1.1 – EEC Low Voltage

Alarm Function

The Electronic Engine Controller (EEC) features a low-side output capable of sinking up to one (1) amp DC to activate an OEM-supplied external alarm. The alarm is triggered based on the following conditions:

Low Fuel: Alarm output cycles two (2) times per second.
Check Engine or Low Voltage (below 11.9 VDC): Alarm output cycles four (4) times per second.
Stop Engine: Alarm output cycles eight (8) times per second.

The EEC activates the low voltage alarm when the system voltage drops below 11.9 VDC. However, the Detroit Diesel Electronic Controls (DDEC) system does not log a low voltage code (PID 168 – FMI 1 / Flash Code 46) or illuminate the Check Engine Light (CEL) unless the voltage drops below:

10.0 VDC in a 12 VDC system
20.0 VDC in a 24 VDC system

Figure 1.2 – Battery Volts (11.8 VDC)

Information Center Display Messages

The EEC Information Center provides real-time status messages based on engine and system conditions. The following messages may be displayed:

Welcome to Detroit Diesel Electronic Engine Commander – Displayed at ignition ON (optional).
Engine Commander – Indicates that the OEM interlock is not active.
PSG: Ready – Interlocks are active, but no RPM/PSI has been requested.
RPM Active – RPM mode has been requested.
Pressure Active – PSI (kPa) mode has been requested.
Preset RPM: XXXX – “Auto-INCREASE/DECREASE” flashes when a preset RPM is requested.
Preset PSI (kPa): XXX – “Auto-INCREASE/DECREASE” flashes when a preset PSI (kPa) is requested.
PSG: Idle Request – Interlock lost or idle switch pressed.
Coolant Temp High – Engine coolant temperature is too high.
Oil Temp High – Engine oil temperature is too high.
Oil Pressure Low – Engine oil pressure is too low.
Coolant Level Low – Engine coolant level is too low.
EEC Low Voltage – EEC voltage has dropped below the acceptable threshold.
Check Engine – DDEC has detected and broadcasted a check engine code.
Stop Engine – DDEC has detected and broadcasted a stop engine code.
EEC Preset Fault – Operating beyond the preset parameters.
PSG Disabled – The digital output for “Cruise Active (PSG)” is missing. Wiring should be checked.

Figure 1.3 – Battery Potential (11.4 VDC – Instrumentation)

Maintaining proper battery voltage is critical to ensure stable EEC operation and prevent alarm activations. Regular monitoring of system voltage and prompt troubleshooting of any alerts can prevent unexpected engine shutdowns.