Navajo 2WD V6-4.0L OHV (1992)
Malfunction Indicator Lamp: Customer Interest
MIL ON, No Self-Test Codes Are Set
Bulletin No.
020/92
Issued
7/10/92
Revised
Category
F
Applicable Model/s
1992 Navajo
Subject
3-DIGIT CODE OVERVIEW
DESCRIPTION
There have been reports of the Malfunction Indicator Lamp (MIL)("Check Engine" or "Service Engine Soon") lamp being lit with no self-test codes in
Continuous Memory. This bulletin contains a brief overview of the 3-digit codes as well as a list of reasons why the MIL lamp may light with no
accompanying Continuous Memory self-test codes stored.
OVERVIEW OF 3-DIGIT SELF-TEST CODES
Mazda introduced 3-digit EEC self-test codes in 1992 to accommodate the increasing number of service codes required to support various government
Onboard Diagnostic (OBD) regulations.
REASONS FOR MIL LAMP ACTIVATION
Following is a list of reasons why the MIL lamp may light when no Continuous Memory self-test codes are present.
1.
Technician Not Familiar with Self-Test Code Output
If a technician is not familiar with the self-test code output, a detailed description of the self-tests is contained in the Workshop Manual, Section
F-16 (EEC Quick Test Procedures and Appendix).
A technician that is unfamiliar with the EEC self-test can mistakenly believe that Continuous Memory codes are not present when they really are.
The technician may run Key On Engine Running (KOER) self-test and get a pass code (111) and not realize that the Key On Engine Off (KOEO)
self-test must be run to receive any Continuous Memory codes. Also, the technician may run the KOEO self-test while counting MIL flashes and
misinterpret the repeated hard fault pass code (111) to mean that the Continuous Memory does not contain any codes.
2.
Inadvertent Erasure of Continuous Memory Self-Test Codes
Continuous Memory self-test codes are erased by ungrounding the Self-Test Input (STI) connector before the KOEO self-test is complete and all
KOEO and Continuous Memory codes have been displayed.
EEC codes are output in two formats: fast and slow. Fast codes are issued prior to regular service codes. These codes contain the same information
as the regular service codes but are transmitted at 100 times the normal rate. These codes can only be interpreted by special equipment at the end
of the assembly line or by code reading testers like the Self-Test Automatic Readout (STAR) testers. After fast codes have been output, self-test
should not be exited until all the slow codes have been output.
Doing this will erase any Continuous Memory codes and could put out a pass code (11/111) next time the KOEO self-test is run.
NOTE:
Some meters detect these fast codes as a short burst of information (a slight meter deflection).
The EEC processor outputs both 2 and 3-digit self-test codes in both fast and slow formats. While all STAR type testers display 2-digit codes, the
original STAR tester cannot display 3-digit service codes. If the original STAR tester is used on 3-digit code applications, the display will be blank
but the tester will beep. The beeps can be counted to determine service codes. The SUPER STAR II tester will only display 3-digit service codes
in "FAST" mode. If "SLOW" mode is used on 3-digit service code applications, the display will be blank but the tester will beep. The beeps can
be counted to determine service codes. For more information on running self-tests, refer to the Navajo Workshop Manual, Section F-16.
