Land Rover Engine Management Systems Rover Manual

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 79
13/14CU AND 14CUX SYSTEMS
Introduction
Three variations of similar Lucas engine management systems have been used on Land Rover 
vehicles from 1987 to selected 1995 models.  Operation of each of these systems is 
fundamentally the same, the differences between each being enhancements to self diagnostics, 
improved adaptability to operating conditions, and additional input/output capability.  All of these 
systems utilize a Engine Control Module, and all are tied to vehicle inputs and outputs through a 
similar 40 pin connector.  
The systems used are:
•  13 CU (1987-88)
•  14 CU (1989)
•  14 CUX (1990-95)
The system control modules are mounted under the passenger seat on 1987-1994 vehicles.  
The module is moved to a position just behind the glove box on 1995 models. 
The ECM works with system inputs and outputs to deliver the best possible combination of 
engine performance and economy while minimizing vehicle emissions.
13 CU
The 13 CU module receives the following inputs:
•  Key on
•  Battery voltage
•  Throttle Position Sensor (TPS)
•  Engine speed
•  Engine Fuel Temperature (EFT) sensor
•  Engine Coolant Temperature Sensor (ECT)
•  Heated Oxygen Sensor (HO2S)
•  Mass Air Flow Sensor (MAF)
•  Vehicle Speed Sensor (VSS)
•  Park/Neutral Position Switch (PNPS) 
•  Air Conditioning Fan and Mode Switch
•  Heated Rear screen load (1987 only) 
						

							13/14CU AND 14CUX SYSTEMS
80 The following are 13 CU outputs:
•  Fuel Injectors
•  Idle Air Control Valve (IACV)
•  Malfunction Indicator Lamp (MIL)
•  Fuel Pump/ Oxygen Sensor Heaters Relay
•  Main relay
13CU System Inputs and Outputs 
						

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 81 14CU and 14CUX
The 14CU and 14CUX modules include additional inputs and output controls for more precise 
control of the air-fuel mixture and enhanced self-diagnostic capabilities.
The following are ECM inputs:
•  Key on
•  Battery voltage
•  Throttle Position Sensor (TPS)
•  Engine speed
•  Engine Fuel Temperature (EFT) sensor
•  Engine Coolant Temperature Sensor (ECT)
•  Heated Front Screen
•  Heated Oxygen Sensor (HO2S)
•  Mass Air Flow Sensor (MAF)
•  Vehicle Speed Sensor (VSS)
•  Park/Neutral Position Switch (PNPS) 
•  Air Conditioning Fan Switch (14CU only)
•  Air Conditioning Thermostat 
The ECM outputs are as follows:
•  Fuel Injectors
•  Idle Air Control Valve (IACV)
•  Purge Valve (CANPV)
•  A/C Compressor Clutch 
•  A/C Condenser Fan Control Module (FCM)
•  Malfunction Indicator Lamp (MIL)
•  Fuel Pump/ Oxygen Sensor Heaters Relay
•  Main relay
•  Fault Code Display Unit (14CUX only) 
						

							13/14CU AND 14CUX SYSTEMS
8214CUX Inputs and Outputs 
						

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 83 SYSTEM INPUTS
Mass Air Flow Sensor (MAF)
The Mass Air Flow (MAF) sensor is a hot-wire type.  It contains two wires, one heated to a 
known value of 100° C (212° F) above the other.  As air flow increases, the current required to 
maintain this difference in temperature increases.  The air flow meters circuitry converts this 
current requirement into a signal the ECM uses to determine the amount of air entering the 
intake manifold.
Typical MAF output voltage at idle is between 1.3 and 1.5 VDC.  A diagnostic trouble code (12) 
is produced if MAF voltage is: 
•  less than 122 mV with RPM in excess of crank speed.
•  greater than 4.96 V with RPM less than 976 for more than 160 milliseconds.
Mass Air Flow Sensor    
						

							13/14CU AND 14CUX SYSTEMS
84 Throttle Position Sensor (TPS)
This potentiometer is mechanically linked to the throttle butterfly and provides an output voltage 
proportional to the butterfly position.   This information allows the ECM to determine throttle 
position and is used for ECM strategies like the following:
•  Acceleration Enhancement - The ECM increases the amount of fuel normally provided for a 
given throttle position during periods of peak acceleration.  This allows the system to antici-
pate fuel needs.
•  Deceleration Fuel Shut-off - During throttle closed deceleration, the ECM does not activate 
fuel injectors (zero pulse-width) to prevent unneeded fuel from entering the cylinders.  This 
strategy protects against catalytic converter overheating and reduces fuel consumption.
13 CU throttle position sensors must be set to an initial output reading of 290-360 mV when 
installed.  Gradual loosening of the TPS or damage to the throttle stop could cause the sensor 
to move out of range.
14 CU and CUX throttle circuitry is adaptable within a range of 80 to 500 mV. Within this range, 
the PCM will adapt to the initial setting and use it as a reference.  There is no need to adjust the 
TPS following installation on these models.  If the TPS should fail, the ECM will use a default 
value of 576 mV and the MIL will be illuminated. 
A diagnostic trouble code (17) is set when sensor output is less than 78 mV for longer than 160 
milliseconds.
Throttle Position Sensor    
						

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 85 Engine Coolant Temperature Sensor (ECTS)
The ECTS is a resistor based sensor.  As coolant temperature increases, sensor resistance 
decreases.  The ECM uses this information for hot- and cold-start strategies that require 
additional fuel delivery.  It also uses this information to help determine when to enter closed loop 
operation.
A diagnostic trouble code (14) is stored when the signal is out of range (0.15V to 4.9V) for 
longer than 160 milliseconds.  The MIL will illuminate and the ECM will substitute a default value 
of 36° C (97° F).
Coolant Temerature Sensor Response
Engine Fuel Temperature Sensor (EFTS)
The fuel temperature sensor, mounted on the fuel rail, operates in the same manner as the 
ECTS.  When the ECM receives a high fuel temperature input, it increases injector pulse during 
hot restarts.  When fuel is hot, vaporization occurs in the fuel rail and bubbles may be found in 
the injectors.  This can lead to hard starting.  Increasing injector pulse time flushes the bubbles 
away and cools the fuel rail with fresh fuel from the tank.  Since 1989, the EFTS has also been 
used by ECM to trigger operation of the radiator fans when under-hood temperatures become 
extreme.
As with the engine coolant temperature sensor, a diagnostic trouble code (15 [14CUX only]) is 
stored when the signal is out of range (0.08V to 4.9V) for longer than 160 milliseconds.  No 
default value is provided by the ECM, however the MIL will illuminate.   
						

							13/14CU AND 14CUX SYSTEMS
86 Heated Oxygen Sensor (HO2S)
The heated oxygen sensor is mounted in each exhaust downpipe and is used by the ECM to 
determine whether the engine is operating rich or lean.  The ECM uses this information to 
increase or decrease injector pulse width to bring the air/fuel ratio as close to Stoichiometric as 
possible.  The ECM monitors each sensor separately and makes fuel trim adjustments to each 
cylinder bank independent of the other.
Typical Heated Oxygen Sensor
Oxygen sensors operate efficiently only when warm.  Heated sensors reach operating 
temperatures quickly to provide accurate information to the ECM soon after start-up and allow 
closed loop operation to occur sooner.  This helps provide an efficient fuel mixture during engine 
warm-up and guards against catalytic converter overheating.
The sensors operate in a range of 0 to 1.1 VDC.  To avoid the possibility of interference in this 
narrow range of operation, each input wire is shielded against RF interference.
Diagnostic trouble codes (44/45) are produced if either HO2S will not switch after the ECM has 
radically altered fueling on that bank of injectors.  The test is performed when the engine is at 
normal operating temperature, TPS input is above 2 volts, and a road speed input is received. 
						

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 87 Park/Neutral Position Switch (PNPS)
The ECM uses this information on transmission gear selection to determine correct positioning 
of the Idle Air Control (IACV) valve.  A diagnostic trouble code (69 [14CUX only]) is set when 
sensor voltage is 5 V during cranking or 0 V with RPM above 2663 and MAFS voltage above 3 
V.   
Engine Speed
The ECM determines engine speed from data received through the negative coil lead.  A 
dropper resistor (6800 ohms) reduces the voltage at the ECM to approximately 7 volts.  The 
ECM requires a pulse from the ignition system before energizing injectors.  
Coil Leads 
						

							13/14CU AND 14CUX SYSTEMS
88 Vehicle Speed Sensor (VSS)
The Vehicle Speed Sensor is located on the left hand side of the frame on early models, and on 
the left hand side of the transfer case on later models.  It informs the ECM when vehicle speed 
is above or below 3 mph.  This information is used by the ECM to ensure that the idle air control 
valve (IACV) is moved to a position to prevent a stall when the vehicle comes to a stop.  DTC 68 
will be displayed if the MAF is greater than 3V at 2000-3000 RPM’s
Vehicle Speed Sensor  1987-1995
      Vehicle Speed Sensor  1995- Onward