LUCAS HOTWIRE (14CUX) - System Overview
A very basic system introduced as the first fuel injection engine management system on the Land Rover V8ís with self diagnostic capability. Found on All defender V8ís except the 50th Anniversary edition and NAS (North American Specification) on all V8 Mk 1 discoveries and on all V8 classic Range Rovers.
SM006 - LUCAS HOTWIRE (14CUX) - System Help file
Version 1.22

LUCAS HOTWIRE (14CUX) - Known Fitments
Vehicle makes, models and variants known or believed to be using this vehicle system, required diagnostic lead and degree of known compatibility.

Vehicle Make Vehicle Model Vehicle Variant Diagnostic Lead
Land Rover Range Rover MK I (Classic) 3.9 / 4.2 V8 Red 14 CUX Lead
Land Rover Defender 3.9 / 4.2 V8 Red 14 CUX Lead
Land Rover Discovery 3.5 / 3.9 V8 Red 14 CUX Lead
Morgan Morgan 3.9 <2000 Red 14 CUX Lead

LUCAS HOTWIRE (14CUX) - Physical Details

Details of the pin usage for the ECU connector(s).

1 Idle air control valve with ignition on – output
2 Engine control relay with ignition on – input
3 Throttle position sensor with ignition on – output
4 Ground
5 Module coding plug – input
6 Vehicle speed sensor while vehicle moving – input
7 Engine coolant temperature sensor with ignition on - input
8 Heated windscreen - input
9 Diagnostic line
10 Malfunction indicating lamp - ground
11 Injectors even numbers (2,4,6,8) - ground
12 Engine control relay - ground
13 Injectors odd numbers (1,3,5,7) - ground
14 Ground
15 Battery voltage - input
16 Fuel pump relay - ground
17 Evaporative emission canister purge valve
18 Diagnostic
19 Ignition switch - input
20 Throttle position sensor - input
21 Air-conditioning refrigerant pressure switch - input
22 Mass air flow sensor - input
23 Left heated oxygen sensor - input
24 Right heated oxygen sensor - input
25 Fuel temperature sensor - ground
26 Idle air control valve while ignition switched on
27 Module coding plug while ignition on - ground
28 Idle air control valve - output
30 MFI fault display unit
31 Data Link Connector - ground
32 Engine fuel temperature sensor
33 Compressor clutch relay
34 Power Mirror Diode-Park/Neutral Position Switch-Neutral Sence Resister
35 Mass Air Flow Sensor
36 Fan Control Module
37 Not Used
38 MFI Fault Display Unit
39 MFI Resister 1
40 Ground

SM006 - LUCAS HOTWIRE (14CUX) - Diagnostic Capabilities (Read Fault Codes)
When the 14CUX system detects a fault it only reports a fault code that indicates the group of faults to which the fault belongs. There are 23 groups, some only having one fault in them and some having several. Thus, very often the reported fault is quite vague (e.g. problem with a specific sensor) but the sensor may be open circuit, short circuit, out of range, intermittent etc.; further inspection is generally required to actually pinpoint the exact failure.

SM006 - LUCAS HOTWIRE (14CUX) - Diagnostic Capabilities (Clear Fault Codes)
This function diagnostically clears the 14CUX ECU's fault code memory although the memory will also clear if the vehicles battery is disconnected.

SM006 - LUCAS HOTWIRE (14CUX) - Diagnostic Capabilities (Inputs)
Realtime live display of the information the electronic control unit of the selected vehicle system is currently deriving from its input sensors.

  • Fuel temperature: This is the value obtained from the fuel temperature sensor, which is located on the metal fuel rail (in between the cylinder heads). When the engine has been running and is then stood for a short time, heat escaping from the engine can super heat the fuel trapped in the fuel rail, meaning that when restarting an already hot engine problems can arise (hot starting problems). Having the fuel temperature information means that the 14CUX ECU can compensate for this by increasing the Injector opening (pulse) period when the fuel temperature is high.
  • Coolant temperature: The value obtained from the engine's coolant temperature sensor.
  • Air flow: This displays the current output from the Air Flow meter.
  • Throttle pot volts: This gives the current throttle pot position.
  • Lambda A: This should toggle from minus figures to plus figures occasionally freezing during normal operation. If it does not, then the sensor may be faulty.
  • Lambda B: This should toggle from minus figures to plus figures occasionally freezing during normal operation. If it does not, then the sensor may be faulty.
  • Injector pulse timing: This displays the current injector pulse timing in milliseconds.
  • Stepper position: This displays the current position of the stepper motor in steps.
  • Road speed: The vehicle's current road speed in miles per hour or kilometres per hour.
  • Engine speed: The engine's current speed in rotations per minute.
  • Purge valve: This displays the status of the purge valve output.
  • Front screen: This is an input which tells the 14CUX ECU that the heated front windscreen is being switched on so that it can compensate for the heavier electrical load on the alternator.
  • Auto gearbox: (Automatics only) Used by the 14CUX ECU to tell when the Gearbox is in gear so that it may compensate for the extra load that the gearbox imposes. On a manual gearbox this will always read drive.
  • Air con: This is an input which tells the 14CUX ECU that the Air Conditioning is being activated that it can compensate for the heavier load imposed by the pump.