1999 TOYOTA CAMRY Service Repair Manual

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Page 2193 of 4592

TOYOTA CAMRY 1999 Service Repair Manual DI±42
± DIAGNOSTICSENGINE
2 Connect OBD II scan tool or TOYOTA hand±held tester, and read value for volt-
age output of A/F sensor (bank 1 sensor 1).
PREPARATION:
(a) Connect the OBD II scan tool

Page 2194 of 4592

TOYOTA CAMRY 1999 Service Repair Manual ± DIAGNOSTICSENGINE
DI±43
NG Replace A/F sensor.
OK
5 Check air induction system (See Pub. No. RM654U, page SF±1).
NG Replace or replace.
OK
6 Check EGR system (See Pub. No. RM654U, page EC±12).
N

Page 2195 of 4592

TOYOTA CAMRY 1999 Service Repair Manual DI±44
± DIAGNOSTICSENGINE
NG Repair or replace.
OK
Replace A/F sensor (bank 1 sensor 1).
10 Perform confirmation driving pattern (See page DI±79).
Go
11 Is there DTC P0125 being output again?
YES C

Page 2196 of 4592

TOYOTA CAMRY 1999 Service Repair Manual ± DIAGNOSTICSENGINE
DI±45
DTC P0136 Oxygen Sensor Circuit Malfunction (Bank 1
Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI±40.
DTC No.DTC Detecting ConditionTrouble Area
P0136
Voltag

Page 2197 of 4592

TOYOTA CAMRY 1999 Service Repair Manual DI±46
± DIAGNOSTICSENGINE
CHECK:
Read the voltage output of the heated oxygen sensor when the engine is suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 min. using the accelerator pedal.
OK

Page 2198 of 4592

TOYOTA CAMRY 1999 Service Repair Manual A09296BE6653A09265
ON
HT2
(±) (+)
± DIAGNOSTICSENGINE
DI±47
DTC P0141 Oxygen Sensor Heater Circuit Malfunction
(Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI±40.
DTC No.DTC De

Page 2199 of 4592

TOYOTA CAMRY 1999 Service Repair Manual DI±48
± DIAGNOSTICSENGINE
2 Check resistance of heated oxygen sensor heater (See Pub. No. RM654U, page
SF±63).
NG Replace heated oxygen sensor.
OK
Check and repair harness or connector between EFI

Page 2200 of 4592

TOYOTA CAMRY 1999 Service Repair Manual ± DIAGNOSTICSENGINE
DI±49
DTC P0171 System too Lean (Fuel Trim)
DTC P0172 System too Rich (Fuel Trim)
CIRCUIT DESCRIPTION
Fuel trim refers to the feedback compensation value compared to the basic in

± DIAGNOSTICSENGINE
DI±49
DTC P0171 System too Lean (Fuel Trim)
DTC P0172 System too Rich (Fuel Trim)
CIRCUIT DESCRIPTION
Fuel trim refers to the feedback compensation value compared to the basic injection time. Fuel trim includes
short±term fuel trim and long±term fuel trim.
Short±term fuel trim is the short±term fuel compensation used to maintain the air±fuel ratio at its ideal
theoretical value.
The signal from the A/F sensor is approximately proportional to the existing air±fuel ratio, and ECM compar-
ing it with the ideal theoretical value, the ECM reduces fuel volume immediately if the air±fuel ratio is rich
and increases fuel volume if it is lean.
Long±term fuel trim compensates for the deviation from the central value of the short±term fuel trim stored
up by each engine tolerance, and the deviation from the central value due to the passage of time and
changes of environment.
If both the short±term fuel trim and long±term fuel trim exceed a certain value, it is detected as a malfunction
and the MIL lights up.
DTC No.DTC Detecting ConditionTrouble Area
P0171
When air±fuel ratio feedback is stable after engine warming up,
fuel trim is considerably in error on RICH side
(2 trip detection logic)
Air induction system
Injector blockage
Manifold absolute pressure sensor
Engine coolant temp. sensor
Fuel shutoff valve for delivery pipe
Gas leakage on exhaust system
Air induction system
Open or short in A/F sensor (bank 1 sensor 1) circuit
A/F sensor (bank 1 sensor 1)
ECM
P0172
When air±fuel ratio feedback is stable after engine warming up,
fuel trim is considerably in error on LEAN side
(2 trip detection logic)
Injector leak, blockage
Manifold absolute pressure sensor
Engine coolant temp. sensor
Ignition system
Fuel shutoff valve for delivery pipe
Gas leakage on exhaust system
Open or short in A/F sensor (bank 1 sensor 1) circuit
A/F sensor (bank 1 sensor 1)
ECM
HINT:
When the DTC P0171 is recorded, the actual air±fuel ratio is on the LEAN side. When DTC P0172 is
recorded, the actual air±fuel ratio is on the RICH side.
If the vehicle runs out of fuel, the air±fuel ratio is lean and DTC P0171 is recorded. The MIL then comes
on.
If the total of the short±term fuel trim value and long±term fuel trim value is within +38 %, the system
is functioning normally.
The A/F sensor output voltage and the short±term fuel trim value can be read using the OBD II scan
tool or TOYOTA hand±held tester.
DI1JW±04

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