What are the codes for the ECU on a 1990 240sx?

Diagnostic codes for 1989 to 1992 240 sx.to swith the modes - turn the ignition switch on. Turn the diagnostic mode selector located on the side of the ECU control unit 1 turn clockwise. The LED lamps will start to flash. Count the flashes until the number for the desired MODE is reached and then IMMEDIATELY turn the diagnostic mode selector located on the side of the ECU control unit 1 turn COUNTER clockwise. (if the mode selector is kept turned clockwise, the unit will continue to change in the order of MODE 1 , 2 , 3 etc.)ECU diagnostic memory will be LOST if the battery is disconnected OR if MODE 4 is selected after selecting MODE 3.Results are kept in memory until the starter is operated 50 times after an item is judged to be malfunctioning, at which time the result is cancelled. If the same item is judged to malfuncting again BEFORE the starter is used 50 times, it will be stored again and the memory will be stored until the starter has been used 50 times from that point.

MODE 1 - During closed loop operation, green light is on when a lean condition is detected, and off when a rich condition is detected. (during open loop operation, red lamp stays off)

MODE 2 - Green lamp function is the same as in MODE 1. During closed loop operation, the red lamp turns ON and OFF simultaneously with the green lamp when the mixture ratio is controlled within the specified values. (during open loop operation, red lamp stays off)

MODE 3 - Red lamp flashes first and indicates units of 10. Green lamp indicates units of 1. (i.e.- 1 red 2 green =12)

When engine fails to start, crank it 2 or more times BEFORE beginning self-diagnostic. DO NOT erase the stored memory, or intermittent malfunction information will be lost.

code item Calif non calif11 Crank angls sensor output yes yes12 Air flow meter circuit yes yes13 Engine temperature sensor yes yes14 Veicle speed sensor yes yes21 Ignition signal missing in primary coil yes yes31 E.C.U. (ECCS control unit) yes yes32 EGR function yes33 Exhaust gas sensor unit yes yes35 Exhaust gas temperature sensor yes43 Throttle sensor circuit yes yes45 Injector leak yes55 No malfunctions in the above circuit yes yes

MODE 4 - The inspection lamps monitor the ON / OFF condition of the idle switch, starter switch and vehicle speed sensor. Idle switch, starter switch - the on/off status of these switches as detected when MODE 4 is selected is stored in the ECU. When either swith is turned on to off or off to on, the RED led will come on or goes off each time switching is detected. Speed sensor - the on/off status of these switches as detected when MODE 4 is selected is stored in the ECU. When vehicle spped is 12 mph (20 km/h) or slower, the green LED on ECU is OFF. When speed exceeds 12 mph, green LED on ECU comes on.

MODE 5 - Real time diagnosis - the moment a malfunction is detected, the display will be presented immediately by flashing the inspection lamps during a test drive. Compared to self diagnosis, real time is very sensitive and can detect malfunctions in a moment. ITEM REGARDED TO BE BE MALFUNCTIONS IN THIS MODE ARE NOT STORED IN THE ECU MEMORY. A malfunction is indicated if any of the following items is judged to be faulty: Crank angle sensor Ignition signal Air flow meter output signal Fuel pump (some models)

Info as provided by CHILTONS

Jericho jay