Toyota 1KZ-TE Repair Manual page 67

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DI- -4
DLC3
1KZ- -TE ENGINE SUP (RM790E)
DIAGNOSTICS
FI2547
Hand--held Tester
A15042
- - ENGINE
PRE- -CHECK
1. DIAGNOSIS SYSTEM
(a ) De scrip tio n
When troubleshooting Multiplex OBD (M--OBD) ve-
S
hicles, the only difference from the usual trouble-
shooting procedure is that you need to connect the
vehicle to the hand--held tester, and read off various
data output from the vehicle's engine ECU.
The vehicle's on--board computer lights up the
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check engine warning light on the instrument panel
when the computer detects a malfunction in the
computer itself or in drive system components. In
addition to the check engine warning light lighting
up when a malfunction is detected, the applicable
diagnostic trouble codes are recorded in the engine
ECU memory. (See page DI--14)
If the malfunction has been repaired, the check engine warning
light goes off automatically but the diagnostic trouble codes re-
main recorded in the engine ECU memory.
To check the diagnostic trouble codes, connect the
S
hand--held tester to the Data Link Connector 3
(DLC3) on the vehicle or read the number of blinks
of the check engine warning light when TC and CG
terminals on the DLC3 are connected. The hand--
held tester also enables you to erase the diagnostic
trouble codes and activate the several actuators
and check freeze frame date and various forms of
engine data. (For operating instructions, see the
hand--held tester instruction book.)
The diagnosis system operates in the normal mode
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during a normal vehicle use. It also has a check
(test) mode for technicians to simulate malfunction
symptoms and troubleshoot. Some diagnostic
trouble codes use 2 trip detection logic* to prevent
an erroneous detection and ensure thorough the
malfunction detection. By switching the engine
ECU to the check (test) mode using hand--held tes-
ter when troubleshooting, a technician can cause
the check engine warning light to light up for a mal-
function that is only detected once or momentarily.
(hand--held
1KZ-TE PAGES FROM SUPPLEMENT
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tester only) (See page DI--14)
DI8FD- -01
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