14CUXCodeReader

LAND ROVER DIAGNOSTIC CODE READER (already fitted to ISIS Imports sourced 14CUX Plus 8s in the US but none other)
by Lorne Goldman (updated October 2024)

The fuel injection fault display can normally be found at the rear of the glovebox on US 14CUX Plus 8s. It provides two-digit diagnostic codes in a way that's very easy to read if you know how it works. The display has a dark red, transparent, molded plastic case. Light emitting diodes can be seen through the side of the case when a fault code is displayed.

If multiple faults exist, the display shows the one that the ECU thinks is highest priority. Higher priority faults need to be "cleared" before lower priority faults will be displayed. A blank (black) display usually indicates there are no faults..(which makes people think it is not working!).

Use this procedure to clear faults:

1. Switch "on" the ignition.

2. Disconnect the serial link mating plug, wait five seconds, and reconnect.

3. Switch "off" the ignition, and wait several seconds.

4. Switch "on" the ignition. The display should now reset.

October, 2024 update. Sorry for the delay. I tend to primarily focus most on stock Morgans rather than the various variants found elsewhere and all their minutiae. These super useful, bespoke diagnostic units were installed on all North American Spec (NAS) Land Rover (Disco, RR, Defender 1990-1995) vehicles by law. The late and dearly missed Bill Fink did so on his 14CUX Plus 8. I have yet to find one on a Cantab car. Can a Cantab Plus 8 owner from 1990-1995 confirm that to me?

They were not standard on UK cars, whether LR or Morgan or TVR. This has created an unusual situation. If you buy one, whether you are retailer or owner, from the UK, you will be asked something in the neighborhood of 800-1000$ (or £s if you wish). If you are patient and search North America, you can get one for as little as 29$. Fault codes, different from the US OBD2, below.

MORGAN MOTOR COMPANY DIAGNOSTIC CODE READER

by Lorne Goldman

The early unit of these was quite flexible. It can read (and reset) all readable Morgan EFI systems until 2004. Only a few were made. It comes with a close-to-incomprehensible manual (sad smile) and all plugs to interface with old relevant models using Ford, Rover or Land Rover or BMW.

Note: It should then either show a lower priority fault code or appear dark.

14CUX PLUS 8 & PLUS 4 HOTWIRE FAULT CODES
1. Switch ignition on.

2. Disconnect serial link mating plug, wait 5 seconds, then reconnect.

3. Switch ignition off and wait for main relay to drop out.

4. Switch ignition on. The display should now be reset. If there are other faults, the next one will be displayed. Otherwise the display will be black.

5, If there is more than one fault repeat these steps to clear each fault until the display is blank.
If you clear a code without performing a repair it (and the EFI light) may or may not return. Some codes are set by intermittent conditions that do not occur often. Other codes signal serious faults that are detected immediately upon startup.


FAULT CODE	FAULT DESCRIPTION	ACTION
Nothing shown on display	Either nothing is wrong (most likely) or the display is broken
2	Power interruption	This code means power to the ECU has been disconnected and the car has not yet been started. This code should go away as soon as the vehicle is started for the first time. Appearance of this code while driving may signal a problem within the ECU.
12	mass airflow sensor	Usually signals a problem with the airflow meter or the connector which can fall apart or become damaged. Use correct continuity test procedure. TEST
14	engine coolant temp THERMISTER	TEST
15	engine fuel temp sensor	TEST
17	Throttle position sensor	Usually indicates a problem. Refer to the correct continuity tests TEST
18	high throttle positition vs. low mass airflow readings	Usually indicates a problem. Refer to the correct continuity tests TEST
19	low throttle position reading vs. a high mass airflow readout	Usually indicates a problem. Refer to the correct continuity tests TEST
21	tune resistor fault	Identifies that the tune resistor is open circuit-refer to tune resistor test. The tune resistor is embedded in the wire harness. This code may indicate it is damaged. TEST
23	fuel supply fault	Check fuel system pressure and the appropriate continuity test.TEST
25	Ignition misfire	This code indicates that an ignition system misfire has been detected. Codes 40 or 50 indicate on which bank the misfire has occurred.
28	engine air leak	One way to check for small leaks is by spraying choke cleaner (aka ether) at the joint you want to check while the motor is idling. A change in tone indicates the choke cleaner is being sucked into the engine. Check for air leaks in the following areas: Hose, air flow meter to plenum Breather system hoses to plenum Brake servo hose Vacuum reservoir hose (fresh air solenoid) Distributor vacuum advance Hose, purge valce to plenum Injector seals Joint - bypass air valve to plenum plenum chamber to ram housing ram housing to inlet manifold inlet manifold to cylinder head bypass air valve
29	ECM memory fault (if code 29 is showing any other codes are unreliable and must be ignored).	If this code appears all other faults are unreliable and must be ignored. Use the procedure below to clear the code and see if it re-appears. If it does, your ECU is almost certainly bad. Procedure: leave battery connected switch ignition off wait for approximately 5 seconds disconnect ECU plug. reconnect ECU plug switch ignition on and check display unit. If fault code 29 is detected again, swap out the ECU for another and retest.
34	left bank injector fault	The display will indicate if the injector(s) are causing the engine to run rich or lean. If the bank is running rich, check for - faulty injector wiring and connectors, stuck open injectors. If the bank is running lean, check for - faulty injector wiring and connectors, blocked injectors. TEST
36	right bank injector fault	As code 34, except relevant to bank A injectors. TEST
40	left bank misfire	If one fault code 40 or 50 is displayed check components applicable to the particular bank that the misfire has occurred on: Spark plugs Ignition leads Distributor cap Injectors - if code 34 bank A or 36 bank B displayed If both codes are displayed, check the following components common to both banks: Distributor cap Distributor rotor Coil and its associated connections Distributor pick-up (air gap) Amplifier Injectors (if code 34 or 36 is displayed)
44	left bank headed O2 sensor fault	If one of these fault codes (#44 or #45) is displayed check the wiring to that particular lambda sensor. In addition this fault will be displayed if the vehicle has a condition which causes it to run very lean or very rich on one side (example - a vacuum leak or a bad injector). This code often appears in conjunction with the misfire codes in cases of bad ignition misfire (cross-firing plug wires) If both codes are displayed, the voltage supply to the heater coils of the sensors must be checked. Check for 12V appearing on the O2 signal lead, and check the heater circuit for shorts. TEST
45	right bank heated O2 sensor fault	If one of these fault codes (#44 or #45) is displayed check the wiring to that particular lambda sensor. In addition this fault will be displayed if the vehicle has a condition which causes it to run very lean or very rich on one side (example - a vacuum leak or a bad injector). This code often appears in conjunction with the misfire codes in cases of bad ignition misfire (cross-firing plug wires) If both codes are displayed, the voltage supply to the heater coils of the sensors must be checked. Check for 12V appearing on the O2 signal lead, and check the heater circuit for shorts. TEST
48	idle air control valve fault (IAVC) aka Stepper Motor	TEST
50	right bank misfire	If one fault code 40 or 50 is displayed check components applicable to the particular bank that the misfire has occurred on: Spark plugs Ignition leads Distributor cap Injectors - if code 34 bank A or 36 bank B displayed If both codes are displayed, check the following components common to both banks: Distributor cap Distributor rotor Coil and its associated connections Distributor pick-up (air gap) Amplifier Injectors (if code 34 or 36 is displayed)
58	Group faults 23/28	This indicates that a fault has been registered that is caused by the fuel supply or an air leak but the exact fault cannot be identified. Check all items outlined under codes 23 and 28.
59	Fuel thermistor	TEST
68	Road speed sensor	TEST
88	canister purge valve leak	Refer to test 9 and 10 of the continuity test procedure. TEST