exhaust TOYOTA CAMRY 1999 Service Owner's Manual

± DIAGNOSTICSENGINE (5S±FE)
DI±65
300 Author: Date:
9 Check gas leakage on exhaust system.
NG Repair or replace.
OK
Replace oxygen sensor
(bank 1 sensor 1).
10 Perform confirmation driving pattern (See page DI±152).
Go
11 Is there DTC P0125 being output again?
YES Check and replace ECM.
NO
12 Did vehicle runs out of fuel in the past?
NO Check for intermittent problems.
YES
DTC P0125 is caused by running out of fuel.

± DIAGNOSTICSENGINE (5S±FE)
DI±79
314 Author: Date:
DTC P0171 System too Lean (Fuel Trim)
(Only for California Spec.)
DTC P0172 System too Rich (Fuel Trim)
(Only for California Spec.)
CIRCUIT DESCRIPTION
Fuel trim refers to the feedback compensation value compared against 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 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 using 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)

Gas leakage on exhaust system

Air intake (loose hoses)

Fuel line pressure

Injector blockage

Manifold absolute pressure sensor

Engine coolant temp. sensor

A/F sensor
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)

Gas leakage on exhaust system

Fuel line pressure

Injector leak, blockage

Manifold absolute pressure sensor

Engine coolant temp. sensor

A/F sensor
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.

The ECM controls the voltage of AF
and AF terminals of ECM to the fixed voltage. Therefore, it
is impossible to confirm the A/F sensor output voltage without OBD II scan tool or TOYOTA hand±held
tester.
DI1JW±03

± DIAGNOSTICSENGINE (5S±FE)
DI±81
316 Author: Date:
5 Check fuel pressure (See page SF±6).
NG Check and repair fuel pump, pressure regulator,
fuel pipe line and filter.
OK
6 Check gas leakage on exhaust system.
NG Repair or replace.
OK
Check and replace ECM (See page IN±31).

DI±84
± DIAGNOSTICSENGINE (5S±FE)
319 Author: Date:
DTC P0171 System too Lean (Fuel Trim)
(Except California Spec.)
DTC P0172 System too Rich (Fuel Trim)
(Except California Spec.)
CIRCUIT DESCRIPTION
Fuel trim refers to the feedback compensation value compared against 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 heated oxygen sensor indicates whether the air±fuel ratio is RICH or
LEAN compared to the ideal theoretical value, triggering a reduction in fuel volume if the air±fuel ratio is rich,
and an increase in fuel volume if it is lean.
Long±term fuel trim is overall fuel compensation carried out long±term to compensate for continual deviation
of the short±term fuel trim from the central value due to individual engine differences, wear over time and
changes in the usage environment.
If both the short±term fuel trim and long±term fuel trim are LEAN or RICH beyond 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)

Gas leakage on exhaust system

Air intake (hose loose)

Fuel line pressure

Injector blockage

Heated oxygen sensor (bank 1 sensor 1)

Manifold absolute pressure sensor

Engine coolant temp. sensor
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)

Gas leakage on exhaust system

Fuel line pressure

Injector leak, blockage

Heated oxygen sensor (bank 1 sensor 1)

Manifold absolute pressure sensor

Engine coolant temp. sensor
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 heated oxygen sensor (bank 1 sensor 1) output voltage and the short±term fuel trim value can
be read using the OBD II scan tool or TOYOTA hand±held tester.
DI4NG±01

DI±86
± DIAGNOSTICSENGINE (5S±FE)
321 Author: Date:
5 Check fuel pressure (See page SF±6).
NG Check and repair fuel pump, pressure regulator,
fuel pipe line and filter.
OK
6 Check gas leakage on exhaust system.
NG Repair or replace.
OK
Check and replace ECM (See page IN±31).

± DIAGNOSTICSENGINE (5S±FE)
DI±103
338 Author: Date:
DTC P0340 Camshaft Position Sensor Circuit
Malfunction
CIRCUIT DESCRIPTION
Camshaft position sensor (G signal) consist of signal plate and pickup coil.
The G signal plate has one tooth on its outer circumference and is mounted on the exhaust camshaft.
When the camshafts rotate, the protrusion on the signal plate and the air gap on the pickup coil change,
causing fluctuations in the magnetic field and generating an electromotive force in the pickup coil.
The NE signal plate has 34 teeth and is mounted on the crankshaft. The NE signal sensor generates 34
signals for every engine revolution. The ECM detects the standard crankshaft angle based on the G signals
and the actual crankshaft angle and the engine speed by the NE signals.
DTC No.DTC Detecting ConditionTrouble Area
P0340
No camshaft position sensor signal to ECM during cranking
(2 trip detection logic)
Open or short in camshaft position sensor circuit

Camshaft position sensor
Di t ib tP0340No camshaft position sensor signal to ECM with engine speed
600 rpm or more
Distributor

Starter

ECM
WIRING DIAGRAM
Refer to DTC P0335 (Crankshaft Position Sensor ºAº Circuit Malfunction) on page DI±100.
DI014±09

P25430
ECM
Throttle Body
EGR
Vacuum
Modulator EGR Valve
VSV
Exhaust Gas Throttle
Valve
u
± DIAGNOSTICSENGINE (5S±FE)
DI±105
340 Author: Date:
DTC P0401 Exhaust Gas Recirculation Flow Insufficient
Detected
CIRCUIT DESCRIPTION
The EGR system recirculates exhaust gas, which is controlled to the proper quantity to suit the driving condi-
tions, into the intake air mixture to slow down combustion, reduce the combustion temperature and reduce
NOx emissions. The amount of EGR is regulated by the EGR vacuum modulator according to the engine
load.
If even one of the following conditions is fulfilled, the VSV is
turned ON by a signal from the ECM.
This results in atmospheric air acting on the EGR valve, closing
the EGR valve and shutting off the exhaust gas (EGR cut±off).
Under the following conditions, EGR is cut to maintain driveabil-
ity.

Before engine is warmed up.

During deceleration (throttle valve closed).

Light engine load (amount of intake air very small).

Engine idling.

Engine speed over 4,400 rpm.

High engine load (amount of intake air very large).
DTC No.DTC Detecting ConditionTrouble Area
P0401
After engine is warmed up, intake manifold absolute pressure
is larger than value calculated by ECM while EGR system is
ON
(2 trip detection logic)

EGR valve stuck closed

Open or short in VSV circuit for EGR

Vacuum or EGR hose disconnected

Manifold absolute pressure sensor

VSV for EGR open or close malfunction

ECM
DI015±05

P20769
Vehicle Speed
60 ~ 80 km/h
(38 ~ 50 mph)
Idling
IG SW OFF
(1)(2)
Warm up
3 ~ 5 min.2 min.
3 ~ 5 min.Time (3)
(4)
(5)(6)
(7)
2 min.
± DIAGNOSTICSENGINE (5S±FE)
DI±107
342 Author: Date:
SYSTEM CHECK DRIVING PATTERN
(1) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(2) Start and warm up the engine with all accessories switched OFF.
(3) Run the vehicle at 60 ~ 80 km/h (38 ~ 50 mph) for 3 min. or more.
(4) Idle the engine for about 2 min.
(5) Do steps (3) and (4) again.
(6) Stop at safe place and turn the ignition switch OFF.
(7) Do steps (2) to (5) again.
(8) Check the READINESS TESTS mode on the OBD II scan tool or TOYOTA hand±held tester.
If COMPL is displayed and the MIL does not light up, the system is normal.
If INCMPL is displayed and the MIL does not light up, run the vehicle again and check it.
HINT:
INCMPL is displayed when either condition (a) or (b) exists.
(a) The system check is incomplete.
(b) There is a malfunction in the system.
If there is a malfunction in the system, the MIL will light up after steps (2) to (5) above are done.
(2 trip detection logic)
INSPECTION PROCEDURE
HINT:

If DTC P0105 (Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction), P0106 (Manifold
Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem) and P0401 (Exhaust
Gas Recirculation Flow Insufficient Detected) are output simultaneously, perform troubleshooting of
DTC P0105 first.

If DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) and P0402 (Exhaust Gas Recir-
culation Flow Excessive Detected) are output simultaneously, perform troubleshooting of DTC P0402
first.

Read freeze frame data using TOYOTA hand±held tester or OBD II scan tool. Because freeze frame
records the engine conditions when the malfunction is detected, when troubleshooting it is useful for
determining whether the vehicle was running or stopped, the engine warmed up or not, the air±fuel
ratio lean or rich, etc. at the time of the malfunction.

± DIAGNOSTICSENGINE (5S±FE)
DI±113
348 Author: Date:
DTC P0402 Exhaust Gas Recirculation Flow Excessive
Detected
CIRCUIT DESCRIPTION
Refer to DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) on page DI±105.
DTC No.DTC Detecting ConditionTrouble Area
P0402
After engine is warmed up, conditions (a) and (b) continue:
(a) Intake manifold absolute pressure is larger than value cal-
culated by ECM while EGR system is ON
(b) Misfiring is detected during idling
(2 trip detection logic)
EGR valve stuck open

Vacuum or EGR hose is connected to wrong post

Manifold absolute pressure sensor

ECM
WIRING DIAGRAM
Refer to DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) on DI±105.
SYSTEM CHECK DRIVING PATTEM
Refer to DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) on DI±105.
INSPECTION PROCEDURE
HINT:

If DTC P0105 (Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction), P0106 (Manifold
Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem) and P0402 (Exhaust
Gas Recirculation Flow Excessive Detected) are output simultaneously, perform troubleshooting of
DTC P0105 first.

If DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) and P0402 (Exhaust Gas Recir-
culation Flow Excessive Detected) are output simultaneously, perform troubleshooting of DTC P0402
first.

Read freeze frame data using TOYOTA hand±held tester or OBD II scan tool. Because freeze frame
records the engine conditions when the malfunction is detected, when troubleshooting it is useful for
determining whether the vehicle was running or stopped, the engine warmed up or not, the air±fuel
ratio lean or rich, etc. at the time of the malfunction.
1 Check connection of vacuum hose and EGR hose (See page EC±12).
NG Repair or replace.
OK
DI016±04

DI±118
± DIAGNOSTICSENGINE (5S±FE)
353 Author: Date:
INSPECTION PROCEDURE
HINT:
Read freeze frame data using TOYOTA hand±held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected, when troubleshooting it is useful for determining
whether the vehicle was running or stopped, the engine warmed up or not, the air±fuel ratio lean or rich, etc.
at the time of the malfunction.
1 Are there any other codes (besides DTC P0420) being output?
YES Go to relevant DTC chart.
NO
2 Check gas leakage on exhaust system.
NG Repair or replace.
OK
3 Check heated oxygen sensor (bank 1 sensor 1) (See page DI±66).
NG Repair or replace.
OK
4 Check heated oxygen sensor (bank 1 sensor 2) (See page DI±77).
NG Repair or replace.
OK
Replace three±way catalytic converter.