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1.4.2 PMU Inputs

PMU input configuration including digital inputs, analog inputs, CAN bus integration, and ignition signal distribution.

12V Switched Input (Pin 7)

Source: Dedicated 18 AWG wire tapped from the ignition signal bus bar (which is fed by PBS-I PINK IGN output — see Keyless Ignition and Ignition Signal Distribution)

Function: Provides switched power reference for PMU logic

Implementation: Dedicated wire through firewall (Grommet 2) direct to PMU Pin 7

Load: ~50mA

See Ignition Signal Distribution for complete wiring architecture.

Digital Inputs (Trigger Sources)

Note: Pin 7 (physical 12V switched input above) is separate from In 7 (digital input channel below). Use "Pin7" in programming for ignition sense, "In7" for headlight status.

Input Function Source Connected to Output Notes
In 1 Horn Button Steering wheel button Out 18 (Horn) Normally open, closes when pressed
In 2 Brake Switch Brake pedal switch Out 21 (Brake Lights) Normally open, closes when pedal pressed
In 3 Reverse Signal Turbolamik aux output (Reverse) Out 22 (Reverse Lights) 12V from TCU when 8HP70 in Reverse
In 4 [Available] - - Available for future expansion
In 5 [Available] - - Available for future expansion
In 6 [Available] - - Available for future expansion
In 7 CT4 SW3 (Headlights) CT4 lever pull Out 23 (DRL) logic 12V when headlights active, disables DRL
In 8 [Available] - - Available for future expansion
In 9 A/C Request Factory TJ A/C button signal Out 17 (A/C Clutch) 12V when factory dash A/C button pressed

Note: Keyless ignition is handled entirely by the self-contained Digital Guard Dawg PBS-I module — PMU is not in the keyless logic path. See Keyless Ignition.

Analog Inputs

Input Physical Pin Range Function Notes
An 1-8 Dedicated 0-5V [Available] Future expansion
An 9-16 OUT17-24 0-20V [Configured as outputs] Dual-purpose pins - currently used as OUT17-24

Current Configuration: An 9-16 configured as outputs (OUT17-24). See PMU Outputs for output assignments.

J1939 Data: Engine oil temperature and coolant temperature are monitored via J1939 CAN bus from ECM (no analog inputs needed).

CAN Bus Integration (J1939)

PMU24 taps into existing J1939 CAN bus as stub connection (no termination).

Bus Topology

[ECM 120Ω] ←--+--+--→ [Cummins Body Harness End 120Ω]
               |  |
               |  [PMU24 - stub tap]
               |
          [Dakota Digital - stub tap]

Physical Connection

  • Tap Location: Cummins body harness (same as Dakota Digital tap)
  • Wire Gauge: 18-20 AWG twisted pair
  • Stub Length: <12" from tap to PMU (keep as short as possible, ideally <6")
  • Termination: None - bus already terminated at ECM + harness end
  • PMU Setting: Disable internal CAN termination in software

J1939 Data Used

SPN Parameter PMU Use
175 Engine Oil Temp Oil cooler fan control (OUT 7)
110 Engine Coolant Temp PS cooler fan control (OUT 8)
190 Engine Speed (RPM) Data logging
100 Engine Oil Pressure Data logging

See PMU Programming for CAN-based logic examples.

Ignition Signal Distribution

PMU Pin 7: 18 AWG wire tapped from the engine-bay distribution off HDP24 Pin 12 (which crosses the firewall from the ignition signal bus bar, fed by PBS-I PINK IGN)

Routing: Engine bay (firewall Pin 12 junction → PMU Pin 7)

Purpose: Shares the same switched supply path as the Cummins ECM 12V — both energize whenever the PBS-I asserts PINK IGN.

Non-critical devices (CT4, SwitchPros, radio, BCDC, camera) tap directly off the cabin-mounted ignition signal bus bar - see Ignition Signal for details.