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Introduction
NHEC0029
The ECM has an on board diagnostic system, which detects malfunctions related to engine sensors or actua-
tors. The ECM also records various emission-related diagnostic information including:
Emission-related diagnostic information SAE Mode
Diagnostic Trouble Code (DTC) Mode 3 of SAE J1979
Freeze Frame data Mode 2 of SAE J1979
System Readiness Test (SRT) code Mode 1 of SAE J1979
1st Trip Diagnostic Trouble Code (1st Trip DTC) Mode 7 of SAE J1979
1st Trip Freeze Frame data
Test values and Test limits Mode 6 of SAE J1979
The above information can be checked using procedures listed in the table below.
X: Applicable —: Not applicable
DTC 1st trip DTC
Freeze Frame
data
1st trip Freeze
Frame data
SRT code Test value
CONSULT-II X X X X X —
GST X X*1 X — X X
*1: 1st trip DTCs for self-diagnoses concerning SRT items cannot be shown on the GST display.
The malfunction indicator lamp (MIL) on the instrument panel lights up when the same malfunction is detected
in two consecutive trips (Two trip detection logic), or when the ECM enters fail-safe mode. (Refer to EC-122.)
Two Trip Detection Logic
NHEC0030
When a malfunction is detected for the first time, 1st trip DTC and 1st trip Freeze Frame data are stored in
the ECM memory. The MIL will not light up at this stage. <1st trip>
If the same malfunction is detected again during the next drive, the DTC and Freeze Frame data are stored
in the ECM memory, and the MIL lights up. The MIL lights up at the same time when the DTC is stored. <2nd
trip> The “trip” in the “Two Trip Detection Logic” means a driving mode in which self-diagnosis is performed
during vehicle operation. Specific on board diagnostic items will cause the ECM to light up or blink the MIL,
and store DTC and Freeze Frame data, even in the 1st trip, as shown below.
X: Applicable —: Not applicable
Items
MIL DTC 1st trip DTC
1st trip 2nd trip
1st trip
displaying
2nd trip
displaying
1st trip
displaying
2nd trip
displaying
Blinking Lighting up Blinking
Lighting
up
Coolant overtemperature enrich-
ment protection — DTC: P0217
— X ——X—X—
Misfire (Possible three way cata-
lyst damage) — DTC: P0300 -
P0306 is being detected
X — — ———X—
Misfire (Possible three way cata-
lyst damage) — DTC: P0300 -
P0306 is being detected
—— X ——X——
Closed loop control
— DTC: P1148, P1168
— X ——X—X—
Fail-safe items (Refer to EC-122.) — X — — X*1 — X*1 —
Except above — — — X — X X X
*1: Except “ECM”
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Introduction
EC-68
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