See Figures 1, 2 and 3
When a fault is noted, the ECU stores an identifying code and illuminates the CHECK ENGINE light. The code will remain in memory until cleared; the dashboard warning lamp may not illuminate during the next ignition cycle if the fault is no longer present. Not all faults noted by the ECU will trigger the dashboard warning lamp although the fault code will be set in memory. For this reason, troubleshooting should be based on the presence of stored codes, not the illumination of the warning lamp while the car is operating.
Stored codes are displayed by a flashing LED on the ECU. When the CHECK ENGINE warning lamp has been on or reported on, lift or remove the carpet from the right front passenger footwell. The ECU is below a protective cover; the LED may be viewed through a small window without removing the ECU cover. Turn the ignition switch ON ; the LED will display any stored codes by rhythmic flashing. Note that 1986-1990 Legends have two LEDs on the controller; one is red and one is amber. The red one will flash the fault codes; the amber one is used during idle adjustment and is not related to this procedure.
Additionally, the Vigor and 1991-93 Legend models are equipped with a service connector in side the cabin of the vehicle. If the service connector is jumpered, the CHECK ENGINE lamp will display the stored codes in the same fashion. The 2-pin service connector is located under the extreme right dashboard on Legend; on Vigor models, it is found behind the right side of the center console, well under the dashboard.
Codes 1-9 are indicated by a series of short flashes; two-digit codes use a number of long flashes for the first digit followed by the appropriate number of short flashes. For example, Code 43 would be indicated by 4 long flashes followed by 3 short flashes. Codes are separated by a longer pause between transmissions. The position of the codes during output can be helpful in diagnostic work. Multiple codes transmitted in isolated order indicate unique occurrences; a display of showing 1-1-1-pause-9-9-9 indicates two problems or problems occurring at different times. An alternating display, such as 1-9-1-9-1, indicates simultaneous occurrences of the faults.
When counting flashes to determine codes, a code not valid for the vehicle may be found. In this case, first recount the flashes to confirm an accurate count. If necessary, turn the ignition switch OFF , then recycle the system and begin the count again. If the Code is not valid for the vehicle, the ECU must be replaced.
On vehicles with automatic transaxles, the S, D or D4lamp may flash with the CHECK ENGINE lamp if certain codes are stored. For Legend this may occur with Codes 6, 7 or 17. On Vigor and Integra it may occur with codes 6, 7 or 13. In all cases, proceed with the diagnosis based on the engine code shown. After repairs, recheck the lamp. If the additional warning lamp is still lit, proceed with diagnosis for that system.
Stored codes are removed from memory by removing power to the ECU. Disconnecting the power may also clear the memories used for other solid-state equipment such as the clock and radio. For this reason, always make note of the radio presets before clearing the system. Additionally, some radios contain anti-theft programming; obtain the owner's code number before clearing the codes.
While disconnecting the battery will clear the memory, this is not the recommended procedure. The memory should be cleared after the ignition is switched OFF by removing the appropriate fuse for at least 10 seconds. The correct fuses and their locations are:
Check Engine Light
The function of the CHECK ENGINE lamp on the dashboard is checked by the ECU every time the ignition is turned ON . The lamp should illuminate for 2 seconds and then extinguish. In normal operation, the lamp should not come on while driving.
If the warning lamp lights while the vehicle is operating, the ECU has sensed a system fault. The fault may be either loss of signal or signal out-of-range, either high or low. Additionally, when the CHECK ENGINE lamp is lit, the ECU has entered the default or fail-safe mode in which fixed values are substituted for the faulty or missing signal.
If, during diagnosis, the service connector is jumpered, the CHECK ENGINE lamp will light, even if no faults are present. When repairs or diagnosis are completed, the memory should be checked for any stored codes and cleared if necessary. Recording and clearing the codes before a diagnostic test drive can be helpful in separating intermittent faults from current or hard faults.