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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 from ECM Ignition Relay output (relay driven by PMU OUT24 when state machine is in RUN or CRANK — see Keyless Ignition)

Function: Provides switched power reference for PMU logic

Implementation: Dedicated wire through firewall (Grommet 2) direct to PMU Pin 7 - NOT from ignition signal bus bar

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 Boomerang Fob Present Bullet 230 transistor output OUT24 logic (ignition) 12V active when RFID fob in range
In 5 Push Button (Start/Stop) Dash momentary button OUT24 logic (state machine) 12V on press; toggles ignition state
In 6 Turbolamik P/N Turbolamik P/N aux output OUT24 logic + crank gate 12V when 8HP70 shifter in P or N
In 7 CT4 SW3 (Headlights) CT4 lever pull Out 14 (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 state machine runs on PMU. OUT24 drives the ECM ignition relay coil and supplies the hardware crank chain (push button → brake → P/N relay → engine-running lockout → Cole Hersee 24213). See Keyless Ignition and Starter System.

Analog Inputs

Input Physical Pin Range Function Notes
An 1-4 Dedicated 0-5V [Available] Future expansion
An 5 Dedicated 0-5V Boost Pressure 0-5V transducer, displayed on ADU7
An 6 Dedicated 0-5V EGT (Exhaust Gas Temp) Thermocouple + amplifier, displayed on ADU7
An 7 Dedicated 0-5V AUX Battery Voltage Voltage divider circuit, displayed on ADU7
An 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).

ADU7 Integration: Analog inputs An 5-8 feed data to ADU7 Display via ECUMaster CAN bus.

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: Dedicated 18 AWG wire directly from ECM Ignition Relay output (NOT from ignition signal bus bar)

Routing: Engine bay (relay → PMU Pin 7), no firewall crossing required

Purpose: Critical PMU functions have guaranteed power independent of other devices

Non-critical devices (CT4, SwitchPros, radio, BCDC, camera) use shared ignition signal bus bar - see Ignition Signal for details.