Engine Fault Codes [D1]

[Slam]

CREDITS: Andy Maier (Moose)

Discoveries have a digital readout for diagnostics located under the passenger seat facing backwards. It is a small black plastic box with a red LED. It may be unclipped from under the seat so you can see it.

These fault codes are given in order of priority so if more than fault exists, you will have to clear the display before the next fault code can be displayed.

NOTE: Fault code 02 means that the ECU has just been reconnected. Switch on the ignition to clear the display. Then disconnect serial link mating plug, wait 5 seconds, then reconnect. Then switch the ignition off and wait for the main relay to drop out. Next switch the ignition on again. After these steps the display should now be reset. If there are other faults, the next one will be displayed. Otherwise the display will be blank.

These are the codes in numerical order.
Code 12 - Airflow meter :: refer to test 19, continuity test procedure.

Code 14 - Coolant thermistor :: refer to test 14, continuity test procedure.

Code 17 - Throttle potentiometer :: refer to test 17, continuity test procedure.


Code 18 - Throttle potentiometer input high/airflow meter low :: refer to tests 17, 18, and 19 of the continuity test procedure.

Code 19 - Throttle potentiometer input low/airflow meter high :: refer to tests 17, 18, and 19 of the continuity test procedure.

Code 21 - fuel tune select :: Identifies that the tune select resistor is open circuit- refer to tune select resistor test.

Code 23 - Fuel supply :: check fuel system pressure, test 20 of continuity test procedure.

Code 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.

Code 28 - Air leak

check for air leaks in the following areas:
o Hose, air flow meter to plenum
o Breather system hoses to plenum
o Brake servo hose
o Vacuum reservoir hose (fresh air solenoid)
o Distributor vacuum advance
o Hose, purge valce to plenum
o Injector seals
o Joint - bypass air valve to plenum plenum chamber to ram housing ram housing to inlet manifold inlet manifold to cylinder head bypass air valve hose

Code 29 - ECU memory check If detected all other faults are unreliable and must be ignored.
Procedure:

1. leave battery connected
2. switch ignition off
3. wait for approximately 5 seconds
4. disconnect ECU plug.
5. reconnect ECU plug
6. switch ignition on and check display unit. If fault code 29 is detected again, swap out the ECU for another one and retest.

If fault code 29 is detected again, swap out the ECU for another one and retest.

Code 34 - Injector bank A 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.

Code 36 - Injector bank B As code 34, except relevant to bank A injectors.
Code 44 - Lambda sensor A - left bank
Code 45 - Lambda sensor B - right bank

If one of these fault codes is displayed check the wiring to that particular lambda sensor.

If both codes are displayed, the voltage supply to the heater coils of the sensors must be checked. Refer to test 26, continuity test procedure.

Code 40 - Misfire bank A - left bank
Code 50 - Misfire bank B - right bank

If both codes are displayed, check the following components common to both banks:
Distributor cap
Rotor arm
Coil
Electrical connectioins
Pick-up (air gap)
Amplifier
Injectors (if code 34 or 36 is displayed)
If either fault code 40 or 50 is displayed check components applicable to the particular bank that the misfire has occurred on.
Spark plugs
HT leads
Distributor cap
Injectors - if code 34 bank A or 36 bank B displayed

Code 48 - Stepper motor check base idle speed- see setting procedure. Refer to tests 15 and 16 of continuity test procedure. Check road speed sensor- refer to test 25 of continuty test procedure.
Code 58 - Group faults 23/28 This indicates that a fault has been registered that is caused by the fuel spply or an air leak but the exact fault cannot be identified. Check all items outlined under codes 23 and 28. Code 59 Fuel thermistor Refer to test 13 of the continuity test procedure.

Code 88 - Purge valve leak refer to test 9 and 10 of the continuity test procedure.

Code 68 - Road speed sensor refer to test 25 of continuity test procedure.

Code 69 - Gearswitch refer to test 24 of continuity test procedure.

 

[kcampbell]

fault codes

As a recent discovery buyer I'm learning more and more about my vehicle but could someone please tell me what a fault code 03 is. I can't find it in any manual that I have.

 

[fbaer]

Which Disco is this for?

 

[Rover2000]

Which Disco is this for?

It must be for the Discovery I because i have a Discovery II and the only thing under the passenger seat is the CD player.

 

[Moose]

It's OBD-I D1.