Land Rover Engine Management Systems Rover Manual

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 89 A/C Fan Switch Input (13CU and 14CU only)
This indicates that heater or A/C blower motor operation has been requested via the dash 
control panel.  On 13CU  systems, this is the only Air Conditioning system input signal.  The 
ECM will compensate for the additional engine load and adjust idle speed accordingly.  On 
14CU systems, this signal is used in combination with the A/C thermostat input signal.
A/C Thermostat Input (14CU and 14CUX only)
By indicating when the A/C compressor is operating, the ECM can compensate for the 
additional engine load and adjust idle speed accordingly.  On 14CU systems this signal comes 
from the A/C thermostat, through the A/C high pressure switch.  On 14CUX, this signal comes 
from the A/C thermostat control unit.
Heated Rear Screen (1987 M.Y. 13 CU only)
By indicating when the heated rear screen is in use, the ECM can compensate for the additional 
load the generator produces on the engine by adjusting the idle speed.  
Heated Front Screen (14 CU and 14 CUX only)
By indicating when the heated front screen is in use, the ECM can compensate for the 
additional load the generator produces on the engine.  The ECM will then adjust the idle speed 
accordingly.
13CU
ECM5
21
PIN
ECM5
21
338
PIN
ECM
21
338
PIN 14CU
14CUX
Heated Rear Screen (1987 only)
A/C Blower Fan/Mode Switch
A/C Thermostat/Pressure Switch
A/C Compressor Clutch Control Heat & A/C Blower Fan Switch
Heated Front Screen
A/C Compressor Clutch Control
Heated Front Screen
A/C Thermostat Unit
Idle (Stepper) Control
Idle (Stepper) Control
Idle (Stepper) Control
, 26, 28, 29
1, 26, 28, 29
1, 26, 28, 29 
						

							13/14CU AND 14CUX SYSTEMS
90 OUTPUTS
Main relay
The ECM provides power to both fuel injector banks, MAFS, the fan module, and fault display 
via the main relay.  The relay is located under the passenger seat on most models.  For 1995, 
the relay has been moved to the engine compartment where it is mounted on the passenger 
side fender wall.  On Defender, the relay is mounted on the passenger side of the bulkhead.
Fuel Pump Relay
The fuel pump relay is located next to the main relay.  The ECM provides power to the fuel 
pump, HO2S heaters and purge valve through the fuel pump relay.  The ECM operates the fuel 
pump for one second at key on and then when it senses a crank/run signal from the ignition 
system.
Relay Locations 1987-1995Relay Locations 1995 
						

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 91 Fuel Injectors
The ECM provides ground side switching to both A (pin 13) and B (pin 11) injector banks.  
Banks are operated alternately except at start-up when simultaneous operation is used to 
provide additional fuel to the system.  Injectors are shut off during deceleration.
The ECM controls fuel volume through injector pulse width.  Pulse width varies between 
approximately 2.4 milliseconds at idle to a maximum of approximately 9.0 milliseconds at full 
load.  Each injector has a resistance of 16 ohms.  Resistance value of the complete injector 
circuit (wired in parallel) will be approximately 4 ohms.  
Idle Air Control Valve (IACV)
The idle air control stepper motor operates through a range of 180 steps with the 0 position 
completely open and the 180 position fully closed.  The further open the valve is positioned, the 
higher the idle speed will be.  Idle position on a vehicle at normal operating temperature with no 
engine load is approximately 160.  The ECM opens the valve a fixed number of steps in 
response to input signals from load producing items such as the air conditioning compressor, 
front defroster, and transmission shifting out of Park/Neutral.  Resistance in the IACV coils 
ranges from 40-60 ohms at room temperature and up to 70 ohms when hot.
Malfunction Indicator Lamp (MIL)
Formerly known as the CHECK ENGINE lamp, the MIL illuminates when the ECM determines 
an emissions-related component has failed.  The MIL also illuminates at key-on and vehicle 
start-up to test bulb operation.
Purge Valve (CAN PV) 14 CU, 14 CUX only
Land Rover vehicles contain an evaporative emission system designed to capture vapors 
produced by the vehicles fuel system.  Evaporative emissions from the fuel tank are trapped in 
a carbon filled canister before they can reach the atmosphere.  These vapors are then vented to 
the plenum chamber through a purge valve during engine operation.  The ECM pulses the valve 
open for short periods below 1700 RPM and holds it open at higher speeds once the engine has 
achieved operating temperature and is in closed loop.  Operating temperature is defined as 
engine coolant temperature above 54° C (130° F). 
The ECM monitors the need for canister purge by looking at HO2S response when the valve is 
opened.  No change in HO2S response with the valve open indicates that the canister has been 
purged of fuel vapor and continued valve operation is no longer necessary.  Operation of the 
purge function when no longer required can negatively impact vehicle emissions.    
A/C Compressor Relay
The ECM controls operation of the electronic A/C clutch through this relay.  The ECM provides 
a ground path for the relay circuit when it receives a request for A/C operation from the A/C 
control panel.
Fan Control Module (FCM)
The ECM remains powered for approximately five seconds after the ignition is switched to OFF.  
During this time, it monitors under-hood temperature through the engine fuel temperature 
sensor.  If measured temperatures exceed 70° C (150° F), the ECM grounds the fan control 
module, allowing the condenser fans to run for ten minutes. 
						

							13/14CU AND 14CUX SYSTEMS
92 Inertia Switch
The inertia switch isolates the power supply to fuel pump in the event of extreme deceleration 
like that which would occur in a collision.  The inertia switch is located under the left front seat 
on 1987-1994 vehicles, and on the bulkhead at the back of the engine compartment from 1995.  
It can be reset by pressing the button at the top of the switch.
Inertia Switch 1987-1994
Inertia Switch 1995 
						

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 93 Engine On-Board Diagnostic (OBD) System 
Much of the new technology introduced on these engine control systems is directed toward 
improving the quality of exhaust gas emissions and reducing air pollution.   Much of this has 
been mandated by legislation that originated with the California Air Resources Board (CARB).  
Control system self-diagnostics, or On-Board Diagnostics (OBD) for vehicle emissions are 
included in the 14 CUX engine control system.   
OBD regulations produced by CARB require that vehicles monitor operation of key emissions 
components such as the oxygen sensor, fuel delivery system, and ECM.  Failure of components 
in these systems is indicated by the illumination of a CHECK ENGINE or Malfunction Indicator 
Lamp (MIL) on the instrument cluster.   
On-board Fault Display Unit
Diagnostic Trouble Codes (DTCs) are provided to help direct the technician to the source of the 
concern.  They can be retrieved with the TestBook or the Lucas HHT. 
Codes are also displayed on 1990-1995 models, via the on-board fault display.  No additional 
diagnostic equipment is required and if a system fault exists, it is displayed any time the ignition 
switch is in the ‘on’ position.  Any additional faults are displayed in order of system priority, but 
only one at a time.  
The following procedure displays the codes, and clears the fault memory:
1  Switch On ignition.
2  Disconnect serial link mating plug, wait 5 seconds, reconnect.
3  Switch OFF ignition, wait for main relay to drop out.
4  Switch ON ignition. The display should now reset. If no other faults exist, and the original 
fault has been rectified, the display will be blank.
5  If multiple faults exist repeat Steps 1 to 4.  As each fault is cleared the code will change, 
until all faults are cleared. The display will now be blank. 
						

							13/14CU AND 14CUX SYSTEMS
94 System Fault Codes
13CU and 14CU systems have a limited number of self-diagnostic fault codes, however all of 
the basic system areas such as Oxygen Sensors, Throttle Potentiometer, Air Flow Sensor, and 
Coolant Sensor are monitored.
14CUX sytems are OBD (I) compliant, and will display the following faults, which are listed in 
order of display priority:
Code Description
02 ECM Power Disconnected (displays only until first key on/key
off cycle)
29 ECM Memory Check
44 Lambda Sensor A
45 Lambda Sensor B
25 Ignition Misfire
40 Misfire Bank A
50 Misfire Bank B
12 Airflow Meter
21 ECM Tune Select
34 Injector Bank A
36 Injector Bank B
14 Coolant temperature Sensor
17 Throttle Potentiometer
18 Throttle Potentiometer high while Airflow Meter low
19 Throttle Potentiometer low while Airflow Meter high
88 Purge Valve
28 Intake System Air Leak
23 Fuel Supply
48 Stepper Motor
68 Road Speed Sensor
69 Automatic Transmission Gear Switch
59 Fuel Supply or Air Leak Group fault
15 Fuel Temperature Sensor     
						

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 95 SYSTEM DIAGNOSTICS
A technicians approach to diagnostics of any vehicle system should include the following steps:
•  Verify the customer concern
•  Determine related symptoms
•  Isolate the source of the concern
•  Perform the required repair
•  Verify system operation
As indicated, the first step in vehicle diagnosis is verification of the customers concern.  This 
can eliminate time spent unnecessarily searching for the cause of a normal operating condition.  
An example of this might be changes in engine idle during times of high accessory load.
The next step in diagnosing the concern is to determine related symptoms and narrow them 
down to a specific vehicle system.  Retrieving diagnostic trouble codes (DTCs) is recommended 
at this stage of diagnosis.  Vehicles using the 13 through 14 CUX series controllers allow limited 
self-diagnostics, including code retrieval, using the TestBook or Hand Held Tester.
Diagnostic Connector
The 14 CUX communicates with diagnostic test equipment (TestBook) through connector pins 
18 and 9.  These pins can be accessed through a harness located under the passenger seat on 
most models.  For the 1995 model year, the harness is located behind the glove box.  Search 
for the harness carefully as it may be tucked in among other wiring.   
						

							13/14CU AND 14CUX SYSTEMS
96 Using this diagnostic connector allows you to perform system diagnostics without removing the 
harness connector from the ECM and clear codes without diagnostic equipment.
Diagnostic Connector Locations 
						

							13/14CU AND 14CUX SYSTEMS
13/14CU and 14CUX Systems 97 TestBook Connections
Selecting the correct accessory cables is critical when using the TestBook for system diagnosis.  
Cables can vary for each application.
Once you have selected the proper cables, ensure that they are securely connected and 
plugged into Socket 1 at the back of the TestBook unit.  Next, connect the clip on the power lead 
to the positive (B+) post of the vehicles battery.  You are now ready to enter TestBook 
diagnostics.
TestBook Diagnostic Connector Hook-up  
Once past the main menu, TestBook offers a selection of vehicle systems that can be tested.  
These include:
•  EFI
•  Air Suspension
•  ABS
•  Airbag
The air suspension selection is available only on Range Rover Classic. 
						

							13/14CU AND 14CUX SYSTEMS
98 Touch the system icon to move on to the next selection screen.
TestBook provides you with the opportunity to monitor the function of the system inputs listed on 
the screen below.