Table of contents: Selecting self-diagnostic modes ↓ Self-diagnosis - Mode III ↓ Self-diagnosis - Mode IV ↓ Self-diagnosis - Mode V ↓ General ↓
1. The ECCS control unit includes self-diagnostics that detect faults in certain components. The fault may be in the component itself or in the wiring, including any associated diodes or relays. See the relevant wiring diagram for details.
2. The ECCS control unit indicates a fault by means of a numerical code displayed by two LEDs, red and green. In Mode III, the red LED lights up first and represents the "tens" of the number, the green one represents the "units". So if the red LED flashes three times and then the green LED flashes twice, this indicates code number 32.
3. It is useful in diagnosing the fault in the main sensors and actuators of the ECCS system. There are five modes of the self-diagnosis system.
Sharp I - Not fitted to UK models.
Sharp II - Not fitted to UK models.
Sharp III - Self-diagnosis - This mode stores all faulty diagnostic units in memory. They will be stored in the ECU memory until the starter is turned on fifty times, or until the ECU power is disconnected.
Mode IV - Switch Diagnostics - In this mode, the idle contacts of the throttle switch, starter switch, vehicle speed sensors and other switches are checked with a repair lamp.
Mode V - Operational diagnostics - Immediately upon detection, the fault will be displayed on the display. This is the mode in which the fault can be observed during a road test.
Selecting self-diagnostic modes
4. Locate the ECCS control unit under the passenger seat, remove the mounting bolts and pull it out. Locate the self-diagnosis selector on the unit and the two LEDs in front of the selector. Ignore the idle speed adjustment recommendations.
5. Turn on the ignition, use a small screwdriver to smoothly turn the selector completely clockwise.
6. When the LEDs light up, count the number of flashes. They will flash once, then twice, three times, four times, five times, then back to once and the cycle will repeat. Each self-diagnosis mode is represented by a corresponding number, for example Mode III - three flashes.
7. When the corresponding number is displayed, immediately turn the selector fully counterclockwise.
8. When the ignition switch is turned off during diagnosis, in any Mode, and then turned on again after the power to the ECCS control unit has completely dropped, the diagnosis will automatically return to Mode 1.
Self-diagnosis - Mode III
9. If a malfunction is suspected, start the engine and warm it up completely to normal operating temperature (if possible). If the engine
does not start, crank it with the starter for at least two seconds before starting the self-diagnosis.
10. Select Mode III (see points 4-7).
11. Look at the LEDs and write down the code displayed (point 2 above); compare it with the table below.
| Display code | Possible damage |
| 11 (1 red flash, 1 green flash) | Distributor/crankshaft angle sensor or chain faulty |
| 12 (1 red flash, 2 green flashes) | Air flow meter or circuit is faulty |
| 13 (1 red flash, 3 green flashes) | Water temperature sensor or circuit is faulty |
| 14 (1 red flash, 4 green flashes) | The vehicle speed sensor or circuit is faulty |
| 21 (2 red flashes, 1 green flash) | Damage to the ignition system. See Section 4 |
| 22 (2 red flashes, 2 green flashes) | The fuel pump or circuit is faulty |
| 23 (2 red flashes, 3 green flashes) | Throttle switch is faulty (idle contact) |
| 24 (2 red flashes, 4 green flashes) | Throttle switch is faulty (fully open throttle contact) |
| 31 (3 red flashes, 1 green flash) | ECCS control unit is faulty |
| 41 (4 red flashes, 1 green flash) | The air temperature sensor or circuit is faulty |
| 55 (5 red flashes, 5 green flashes) | No damage |
12. Erase the memory by turning the selector fully clockwise. After the lamps have flashed 4 times, turn the selector fully counterclockwise. This will erase the signals stored in the ECCS control unit.
13. Turn off the ignition, repair the damage.
Self-diagnosis - Mode IV
14. Turn on the ignition, select Mode IV (see points 4-7 above).
15. Check that the red LED is not lit.
16. Start the engine, the red LED should light when the ignition switch is in the "Start" position. If not, check the ignition switch and battery power (Section 12).
17. With the engine idling, check that the red LED does not light when the accelerator pedal is depressed. If not, check the throttle switch contacts and wiring.
18. Drive the car on the highway, the passenger should check that the green LED lights up when the speed exceeds 20 km / h. If not, check the vehicle speed sensor and wiring.
19. Turn off the ignition.
Self-diagnosis - Mode V
20. Start the engine and select V Mode (see points 4-7 above).
21. Park the vehicle with the engine idling, or drive with a passenger observing the LEDs. As soon as the LEDs start to flash, immediately count and record the number of flashes. In this Mode, the fault code is displayed only once, once the fault is noted by the ECCS control unit, and is not repeated or stored in the memory. Compare the code with the table below.
22. If the LEDs do not light up after five minutes of self-diagnosis, it is possible that no damage was detected in this Mode.
23. Turn off the ignition.
24. Note that this Mode is sensitive enough to detect small defects in wiring and connections, especially dirt or corrosion on terminals. Check all these points in the circuit carefully.
| Display code | Possible damage |
| Red LED flashes once every 3.2 seconds | Distributor/crankshaft angle sensor or chain faulty |
| Green LED flashes twice every 3.2 seconds | Air flow meter or circuit is faulty |
| Green LED flashes four times every 3.2 seconds | Ignition system low voltage circuit faulty |
| Red LED flashes three times every 3.2 seconds | The fuel pump or circuit is faulty |
General
25. If the self-diagnosis procedure indicates damage in any circuit, always check the physical condition of the wiring and connections first. Typically, damage is most often due to loose connections or broken wires.
26. If the wires are in good condition, check the component (as described in this manual if a test procedure is given). If the component is in good condition, the ECCS control unit is probably damaged.
27. Always consult your Nissan dealer before replacing any component.