Reading and Clearing Diagnostic Trouble Codes
READING CODESSELF-DIAGNOSTIC DESCRIPTION
The self-diagnostic system used on Infiniti automobiles uses two modes for performing self-diagnosis. A "CHECK ENGINE" light will illuminate when a malfunction is detected by the ECU to inform the driver that there is a problem.
1. Mode 1 is the normal operating mode that the ECCS system is in whenever the key is on and mode 2 has not been entered.
2. Mode 2:
a. When the key is on and the engine is stopped this is the self-diagnostic mode. The trouble codes will be extracted in this mode.
b. When the engine is running it is used to monitor the air/fuel mixture.
Trouble Code Example:
READING DIAGNOSTIC CODES
The Electronic Control Unit (ECU) monitors several engine sensors and actuators. If a problem occurs the "CHECK ENGINE " light will be turned on until the problem is repaired.
The trouble code(s) will be stored in the ECU's memory for retrieval.
The codes are displayed simultaneously by the "CHECK ENGINE" light and the red diode on the ECU. The codes are interpreted by the number of times and duration the diode flashes.
The "CHECK ENGINE" light and red diode will flash for 0.6 of a second with 0.6 of a second delay between flashes "X" number of times, this will represent units of ten.
Then there will be a delay 0.9 of a second and the "CHECK ENGINE" light and red diode will flash for 0.3 of a second with 0.3 of a second delay between flashes "X" number of times, this will represent units of one.
There will be a delay of 2.1 seconds between codes.
For example, if the "CHECK ENGINE" light and red diode flashes once and then flashes twice rapidly this should be interpreted as code 12. The codes are displayed in numerical order starting with the lowest and ending with the highest.
Fig. 35 Selecting Modes:
EXTRACTING DIAGNOSTIC CODES
1. Access the ECU from the R.F. kick panel and position it for access to the diagnostic mode selector and observing the diode.
2. Turn the ignition switch on (do not start the engine).
3. Confirm that the "CHECK ENGINE" lamp in the instrument panel illuminates.
If not, check the bulb and replace if faulty. If bulb is OK, further electrical circuit testing is required, refer to "Computers and Control Systems".
4. Turn the diagnostic mode selector on the ECU fully clockwise for at least two seconds then turn the selector fully counterclockwise. The ECCS system is now in mode 2.
5. Observe the "CHECK ENGINE" light or diode and note the code(s) displayed.
Note: Code 55 indicates all systems are OK. Refer to DIAGNOSTIC CODE CHART for code identification.
CLEARING CODES
Malfunction codes are erased from the backup memory once the diagnostic mode is switched back from Mode II to Mode I. Non recurring codes are also erased once the starter has been operated 50 times.
NOTE: When the battery terminal is disconnected, the malfunction codes will be lost from backup memory within 24 hours. Do not erase codes before beginning self-diagnosis.