Diag. Code 27 Sub–oxygen Sensor Signal (California Only)
CIRCUIT DESCRIPTION
The sub–oxygen sensor is located in the exhaust pipe behind the TWC. It rechecks the exhaust emission level
after it is purified by the TWC and feeds the results back to the ECU.
Code No.
Diagnosis Trouble Area
27
When sub–oxygen sensor is warmed up and
apply acceleration with the throttle fully
open for 2 seconds, output of main oxygen
sensor is 0.45 V or more (rich) and output
of sub–oxygen sensor is 0.45 V or less
(lean). (OX2) (2 trip detection logic)*
· Short or open in sub–oxygen sensor cir-
cuit.
· Sub–oxygen sensor
· ECU
*: See page TR–13.
DIAGNOSIS CODE DETECTION DRIVING PATTERN
Purpose of the driving patten.
(a) After the diag. code is erased, the malfunction is reproduced and the diag. code is recorded again.
(b) To check that the malfunction is cleared once the repair is completed (confirm that diag. code is no longer
detected).
Malfunction: Open or Short in Sub–Oxygen Sensor
For A/T Vehicle
(1) Start engine and warm engine up.
(2) After engine is warmed up, let it idle for 3 min.
(3) With the A/C ON and the transmission in D range (O/D OFF), drive at 45–70 mph
for 6 min.
(4) After the driving in , stop the vehicle.
(5) Within 1 min. of stopping the vehicle, shift into 2 range and gradually accelerate
for 5 sec. while gradually increasing the engine speed approx. 2,000 rpm. Then,
without releasing the accelerator pedal at all accelerate with throttle wide open for
2 sec.
(6) Stop the vehicle, then 10 sec. or more after turning IG switch to OFF (not Acc),
perform (1), (2), (3), (4), (5) again.
TR–52
–ENGINE TROUBLESHOOTING Circuit Inspection
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