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2.9.1 HDX Control Module

Dakota Digital HDX Control Module

Type: Digital Instrument Control Box

Model: HDX Control Module (Black)

Manufacturer: Dakota Digital

Manual: HDX System Manual

Overview

Main control box for HDX instrument system. Processes sensor inputs, BIM module data, and J1939 CAN bus signals to drive dashboard cluster display.

Mounting: HDPE panel on firewall behind dashboard

Power: PMU OUT9 (25A capacity, CONSTANT power) — TBD #144 (architecture decision: PMU OUT9 vs Critical Cabin PDU Slot 2)

Specifications

  • Dimensions: 5.5" W × 3.5" D × 1" H
  • Power Input: 12V DC (8-23V operating range)
  • Fuse Requirement: 5-20A max (per manufacturer specification)
  • Recommended Fuse: 10A (adequate for entire HDX system including BIM modules)
  • Current Draw: IGN Off ≈ 0.3mA, IGN On ≈ 250-750mA (confirms 10A fuse sizing)
  • BIM Ports: 3.5mm headphone jack (supports up to 16 BIM modules via daisy-chain)
  • Display Output: Proprietary cable to HDX dashboard cluster
  • Configuration: Bluetooth app (iOS/Android) for setup and diagnostics

Input Signal Thresholds:

  • Active High (HIGH, LEFT, RIGHT, GEAR, WAIT, DIM, EX+): Low ≤4V, High ≥8V
  • Active Low (Check/ENGINE, BRAKE, CRUISE, 4x4, EX-): Low ≤8V, High ≥9V
  • Tachometer: Normal mode 3-7.5V, Low-voltage mode 1-4V
  • Speedometer: Square wave >1.2Vp-p or sine wave >1.4Vp-p

Output Capabilities:

  • WARN, SPD outputs: <600mA max

Inputs

Included Sensors:

  • Water temperature sender (100-260°F)
  • Oil pressure sender (0-80 psi)

BIM Module Expansion:

  • J1939 CAN bus interface (BIM-01-2-J1939)
  • GPS speed/compass (GPS-50-2)
  • TPMS (BIM-22-3)
  • Compass/outside temp (BIM-17-2)

Fuel Level:

  • Factory TJ fuel level sender (variable resistance)

Wiring

Connection Pin/Wire Source Destination Notes
DIM ADJ - GND - - - Not used (dash dimming via DIM input instead)
DIM ADJ - SIG - - - Not used (dash dimming via DIM input instead)
FUEL INPUT - GND - Factory TJ fuel sender HDX fuel GND Sender ground
FUEL INPUT - SIG 18 AWG ✓ Factory TJ fuel sender HDX fuel SIG Variable resistance sender signal
PRESSURE INPUT - DRN - Included oil pressure sender HDX pressure DRN Included sensor - OR use J1939 oil pressure
PRESSURE INPUT - GND - Included oil pressure sender HDX pressure GND Included sensor - OR use J1939 oil pressure
PRESSURE INPUT - SIG - Included oil pressure sender HDX pressure SIG Included sensor - OR use J1939 oil pressure
PRESSURE INPUT - PWR - Included oil pressure sender HDX pressure PWR Included sensor - OR use J1939 oil pressure
TEMP INPUT - GND - Included water temp sender HDX temp GND Included sensor - OR use J1939 coolant temp
TEMP INPUT - SIG - Included water temp sender HDX temp SIG Included sensor - OR use J1939 coolant temp
SPEED INPUT - GND - - - Not used (GPS-50-2 provides speedometer via BIM)
SPEED INPUT - SIG - - - Not used (GPS-50-2 provides speedometer via BIM)
SPEED INPUT - PWR - - - Not used (GPS-50-2 provides speedometer via BIM)
CRUISE - - - Not used (no cruise control)
SPD OUT - - - Not used
TACH OUT - - - Not used
TACH WARN - - - Not used (J1939 provides tach via BIM-01-2)
TACH - - - Not used (J1939 provides tach via BIM-01-2)
IGNITION PWR 16 AWG Ignition bus bar HDX ignition input Switched 12V for ignition-controlled features
12 VDC CONSTANT 16 AWG ✓ Critical Cabin PDU Slot 2 (TBD #144) HDX power input 10A fuse, CONSTANT power, ~2 ft
DIM 18 AWG ✓ Tail light circuit HDX DIM input Dash dimming control (variable voltage)
ENGINE 18 AWG ✓ ECM Pin 22 (white wire, MIL) HDX ENGINE input Check engine light / MIL signal — sink-circuit (active low at wire) per Cummins R2.8 Installation Guide 5504137
BRAKE 18 AWG ✓ Brake switch or CT4 HDX BRAKE input Brake pedal indicator
HIGH 18 AWG ✓ CT4 high beam output HDX HIGH input High beam indicator
LEFT 18 AWG ✓ CT4 left turn output HDX LEFT input Left turn indicator
RIGHT 18 AWG ✓ CT4 right turn output HDX RIGHT input Right turn indicator
4x4/EX 18 AWG ✓ 4x4 relay contact (cabin), coil driven by PMU OUT19 HDX 4x4 input Ground-activated — green 4x4 indicator on Home Screen. Relay sinks the input because the PMU is high-side only. Active in 4H or 4L; sensing per Transfer Case (TBD #145)
GEAR - BIM-01-2 J1939 - Gear position read from Turbolamik J1939 broadcast (no discrete input wiring)
WAIT/EX 18 AWG ✓ ECM Pin 35 (yellow wire, WAIT TO START) HDX WAIT/EX input Sink-circuit per Cummins R2.8 Installation Guide 5504137 (§2, ECM pin 35, yellow) — wire is active LOW (~0V when WAIT on, ~+12V when off). HDX input documented as "active high" — polarity bench-verification pending TBD #150.
EX (+) 18 AWG ✓ PMU OUT24 HDX EXTRA(+) input 12V-activated — custom label "4LO" (8 char max), active in 4L only (TBD #145)
EX (−) - - - Reserved (ground-activated spare; fallback 4LO input if the sensor path is dropped)
WARN OUT - - - Not used
SWITCH INPUT - - - Not used (capacitive touch buttons on cluster)
DISPLAY CABLE Proprietary HDX control Dashboard cluster Factory harness included, ~2 ft
CLOCK CABLE - - - Not used (GPS-50-2 provides clock sync via BIM)
BIM I/O Proprietary HDX 3.5mm jack BIM modules Daisy-chain to 4 BIM modules (power + data)
Ground 16 AWG ✓ HDX ground Critical PDU ground bus Shared cabin ground, ~1 ft

BIM Module Integration

All BIM modules connect via single daisy-chain harness from HDX control 3.5mm port:

  • HDX Control → BIM-01-2-J1939 → GPS-50-2 → BIM-22-3 → BIM-17-2
  • Power and data carried over BIM/IO cables (no separate power wiring)
  • Modules auto-detect and configure via Bluetooth app

Outstanding Items

🔴 Critical (2)

High (7)

📋 Medium (3)

  • Horn button → PMU In 1 wiring path through steering column (#152) — PMU In 1 (horn request) lists "steering wheel button" as its source, and the horn page puts the button on the steering-wheel PTT bracket — but no wire path, gauge, or connector is defined for how the button contact reaches PMU In 1 through/around the steering column. Street-legal item with an under-specified signal path.
  • iBooster Wiring Harness Selection (#105) — Select the Bosch iBooster (Gen 2) wiring harness: Tulay's Gen 2 universal (plug-and-play) vs EVcreate Gen 2 connector kit (DIY). Decision pending donor arrival and pigtail condition inspection. Tracked in the purchase tracker but was missing a TBD issue.
  • Axle Brake Flex Hose Length (#86) — DOT (FMVSS 106) braided-stainless extended-length flex at each axle - length blocked on axle + suspension selection (Section 10); size to full droop, do not cut until ride height fixed

🔍 Verify (5)

  • iBooster standby current spec (ignition-off test value) (#151) — The engine-systems testing checklist includes "Verify iBooster standby current within spec (ignition OFF)" but no standby-current spec value is documented anywhere (the brake-booster page does not state one). The test step cannot be completed as written.
  • WAIT-to-start lamp polarity: ECM Pin 35 active-low vs HDX input active-high (#150) — ECM Pin 35 (WAIT lamp, yellow) is active LOW (~0V when WAIT on, ~+12V off); the HDX indicator input is documented as active HIGH. If wired without resolving this, the cold-start indicator reads inverted — and the documented cold-start procedure depends entirely on watching the WAIT lamp.
  • Restomod Air HVAC integration — verify A/C request wiring to PMU In 9 + blower draw (#146) — The factory TJ HVAC is replaced by a custom Restomod Air electronic HVAC kit (ordered, owner-confirmed 2026-06-11) — this resolves the original "no A/C request source post-PCM-delete" gap. Restomod Air kits are fully electronic (servo-driven doors, no vacuum), and the control head generates the A/C request: compressor-engage output (12V) → trinary pressure switch (30/406 psi cutouts) → PMU In 9. PMU logic then drives OUT17 → compressor clutch.
  • AMOT 4261M 2.8″ intake air-path connection OD / reducer coupler to 2.125″ turbo inlet (#129) — The 4261M02 is a wafer butterfly valve that sleeves into a 2.8″ (71 mm) nominal intake duct; the AMOT datasheet (4261M_Air_Shutoff_Valve_0119rev2) publishes only nominal size (71 mm), bore (61 mm / 2.4″), and overall envelope — not the air-path spigot/wafer OD or clamp interface. The NPT thread in part number 4261M02A027-AA (actuator code 27) is the pneumatic control port, not the air path.
  • Grid Heater Current (#42) — Design value 80A - verify via element resistance measurement during installation (~0.15 ohm @ 12V).

Build Tasks

  • Determine brake indicator source (brake switch vs CT4 output)
  • Install 4x4 relay near the HDX; coil ← firewall pin 19, contacts between HDX 4x4 terminal and Firewall Stud Bus ground
  • Set the EXTRA(+) label to "4LO" in the HDX setup menu (8 char max)
  • Verify indicators against actual lever position: 2H = no 4x4, 4H = 4x4 only, 4L = 4x4 + 4LO (TBD #145)
  • Bench-verify WAIT/EX polarity at HDX input — TBD #150: Cummins specifies active-low, HDX docs list "active high"; resolve before final wiring