1996 TOYOTA RAV4 air condition

DI−48
− DIAGNOSTICSENGINE
1996 RAV4 (RM447U)
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 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 ration at its ideal
theoretical value. The signal from the 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 devi-
ation 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 de-
tected as a malfunction and the MIL lights up.
DTC No.DTC Detecting ConditionTrouble Area
P0171
When the air fuel ratio feedback is stable after engine warning
up, the fuel trim is considerably in error on the RICH side
(2 trip detection logic)
Fuel line pressure
Injector blockage
Oxygen sensor malfunction
Manifold absolute pressure sensor
Engine coolant temp. sensor
P0172
When the air fuel ratio feedback is stable after engine warning
up, the fuel trim is considerably in error on the LEAN side
(2 trip detection logic)
Fuel line pressure
Injector blockage, leak
Oxygen sensor malfunction
Manifold absolute pressure sensor
Engine coolant temp. sensor.
HINT:
When DTC P0171 is recorded, the actual air−fuel ratio is on the LEAN side. When DTC P0172 is re-
corded, 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 detected. The MIL then
comes on.
If the total of the short−term fuel trim value and long−term fuel trim value is within ±25 %, the system
is functioning normally.
INSPECTION PROCEDURE
1 Check air induction system (See page SF−1).
NG Repair or replace.
OK
DI3ZN−01

− DIAGNOSTICSENGINE
DI−49
1996 RAV4 (RM447U)
2 Check for oxygen sensor data.
PREPARATION:
(a) Connect the OBDII scan tool or TOYOTA hand−held tester to the DLC3.
(b) Warm up engine to normal operating temperature.
CHECK:
Read the oxygen sensor output voltage and short−term fuel trim.
RESULT:
PatternOxygen sensor output voltageShort−term fuel trim
1Lean condition (Changes at 0.55 V or less)Changes at about +20 %
2Rich condition (Changes at 0.35 V or more)Changes at about −20 %
3Except 1 and 2
3 Check for oxygen sensor
(See page DI−42).
1, 2
3 Check fuel pressure (See page SF−5).
NG Check and repair fuel pump, pressure regulator,
fuel pipe line and filter (See page SF−1).
OK
4 Check injector injection (See page SF−21).
NG Replace injector.
OK
5 Check manifold absolute pressure sensor and engine coolant temp. sensor
(See page DI−21, DI−29).
NG Repair or replace.
OK

− DIAGNOSTICSENGINE
DI−63
1996 RAV4 (RM447U)
DTC P0340 Camshaft Position Sensor Circuit
Malfunction
CIRCUIT DESCRIPTION
Camshaft position sensor (G signal) consist of a signal plate an pickup coil.
The G signal plate has one tooth on its outer circumference and is built into the distributor.
When the camshaft rotate, the protrusion on the signal plate and the air gap on the pickup coil change, caus-
ing 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 signal
and the actual crankshaft angle and the engine speed by the NE signals.
DTC No.Detection ConditionTrouble Area
P0340No camshaft position sensor signal to ECM with engine speed
600 rpm or more
Open or short in camshaft position sensor circuit
Camshaft position sensor
Starter
ECM
WIRING DIAGRAM
Refer to page DI−59 for the WIRING DIAGRAM.
INSPECTION PROCEDURE
1 Check resistance of camshaft position sensor (signal generator) (See page
IG−14).
Reference:
INSPECTION USING OSCILLOSCOPE
Refer to page DI−59 for the OSCILLOSCOPE.
NG Replace camshaft position sensor.
OK
2 Check for open and short in harness and connector between ECM and camshaft
position sensor (See page IN−30).
NG Repair or replace harness or connector.
OK
DI3ZS−01

P25430
Throttle Body
Exhaust GasEGR Valve
Diagram ECM
VSV
Throttle
Valve
Intake Air
Chamber
EGR
Vacuum
Modulator
S02387
From
Battery6
1J2
1
1E J/B No.1EFI Main Relay
Fuse Block
11
10E423
EA12 R/B No.6ECM
J1
Junction Connector
AA
W−B B−W VSV (for EGR)
2
1
B−O
IGNEGR
E01
EAFrom
IG Switch
B−O 666 3
125
R−W
B−RB−R
W−B
− DIAGNOSTICSENGINE
DI−65
1996 RAV4 (RM447U)
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 the following conditions is fulfilled, the VSV is turned
ON by a signal from ECM. This results in atmospheric air acting
on the EGR valve, closing the EGR valve and shutting off the
exhaust gas (EGR cut−off).
Before the 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 the engine is warmed up, the intake manifold absolute
pressure is lager than the valve calculated by the ECM while
the EGR system is ON
(2 trip detected logic)
EGR valve stuck closed
Open or short in VSV circuit for EGR
Vacuum or EGR hose disconnected
Manifold absolute pressure sensor
EGR VSV open or close malfunction
ECM
WIRING DIAGRAM
DI3ZT−01

− DIAGNOSTICSENGINE
DI−71
1996 RAV4 (RM447U)
DTC P0402 Exhaust Gas Recirculation Flow Excessive
Detected
CIRCUIT DESCRIPTION
Refer to Exhaust Gas Recirculation Flow Insufficient Detected on page DI−65.
DTC No.DTC Detecting ConditionTrouble Area
P0402
After the engine is warmed up, conditions (a) and (b) continue
(a) The intake manifold absolute pressure is larger than the
value calculated by the ECM while the 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
See DTC P0140 for System Check Driving Pattern and Wiring Diagram.
INSPECTION PROCEDURE
HINT:
If DTC ”P0105” and / or ”P0106” and ”P0402” are output simultaneously, perform troubleshooting of
DTC ”P0105” first.
If DTC ”P0401” and ”P0402” are output simultaneously, perform troubleshooting of DTC ”P0402” first.
1 Check the connection of the vacuum hose, EGR hose (See page EC−5).
NG Repair or replace.
OK
2 Check EGR valve (See page EC−8).
NG Repair or replace.
OK
3 Check the VSV for EGR * .
* If you have TOYOTA hand−held tester, see page DI−65, step 2.
If you have no TOYOTA hand−held tester, see page DI−65, step 2.
OK Go to step 5.
NG
DI3ZU−01

FI7081
Waveform of oxygen sensor
before catalystNormal
catalystWaveform of oxygen sensor
after catalyst
− DIAGNOSTICSENGINE
DI−73
1996 RAV4 (RM447U)
DTC P0420 Catalyst System Efficiency Below Threshold
CIRCUIT DESCRIPTION
The ECM compares the waveform of the oxygen sensor located before the catalyst with the waveform of
the oxygen sensor located after the catalyst to determine whether or not catalyst performance has deterio-
rated.
Air−fuel ratio feedback compensation keeps the waveform of the oxygen sensor before the catalyst repeat-
edly changing back and forth from rich to lean.
If the catalyst is functioning normally, the waveform of the oxygen sensor after the catalyst switches back
and forth between rich and lean much more slowly than the waveform of the oxygen sensor before the cata-
lyst.
But when both wavaforms change at a similar rate, it indicates that catalyst performance has deteriorated.
DTC NoDTC Detecting ConditionTrouble Area
P0420
After the engine and the catalyst are warmed up, and while the
vehicle is driven within the set vehicle and engine speed range,
the waveforms of the oxygen sensors (bank 1 sensor 1 and
bank 1 sensor 2) have the same amplitude
(2 trip detection logic)
Front TWC (front catalyst) and TWC w/pipe (rear catalyst)
Oxygen sensor
DI3ZV−01

− DIAGNOSTICSENGINE
DI−83
1996 RAV4 (RM447U) DTC No..
DTC Detecting ConditionTrouble Area
P0441
The pressure in the charcoal canister does not drop during
purge control
(2 trip detection logic)
Open or short in VSV circuit for vapor pressure sensor
VSV for vapor pressure sensor
Open or short in vapor pressure sensor circuit
Vapor pressure sensor
Open or short in VSV circuit for EVAP
VSV for EVAP
Vacuum hose cracks, hole, blocked, damaged or discon-
nected ( (1), (4), (5) and (6) in fig. 1 )
Charcoal canister cracks, hole or damaged
During purge cut−off, the pressure in the charcoal canister is
very low compared with atmospheric pressure
(2 trip detection logic)
P0446
When VSV for vapor pressure sensor is OFF, ECM judges that
there is no continuity between vapor pressure sensor and
charcoal canister
(2 trip detection logic)
When VSV for vapor pressure sensor is ON, ECM judges that
there is no continuity between vapor pressure sensor and fuel
tank
(2 trip detection logic)
After the purge cut off operates, the pressure in the charcoal
canister is maintained at atmospheric pressure
(2 trip detection logic)
WIRING DIAGRAM
Refer to Evaporative Emission Control System Malfunction on page DI−76.
INSPECTION PROCEDURE
HINT:
If DTC P0441, P0446 or P0450 is output after DTC P0440, first troubleshoot DTC P0441, P0446 or P0450.
If no malfunction is detected, troubleshoot DTC P0440 next.
TOYOTA hand−held tester
1 Check the VSV connector for EVAP, VSV connector for vapor pressure sensor
and vapor pressure sensor connector for looseness and disconnection.
NG Repair or connect the VSV or sensor connector.
OK
2 Check the vacuum hose between intake manifold and VSV for EVAP,VSV for
EVAP and charcoal canister, charcoal canister and VSV for vapor pressure sen-
sor, and VSV for vapor pressure sensor and vapor pressure sensor.
CHECK:
(a) Check that the vacuum hose is connected correctly.
(b) Check the vacuum hose for looseness and disconnection.
(c) Check the vacuum hose for cracks, hole, damage, and blockage.
NG Repair or replace.

P01559
From
Air
CleanerThrottle valve
Signals
Valve IAC Valve
To Cylinders ECM
Intake
Air
Chamber
− DIAGNOSTICSENGINE
DI−97
1996 RAV4 (RM447U)
DTC P0505 Idle Control System Malfunction
CIRCUIT DESCRIPTION
The rotary solenoid type IAC valve is located on the throttle
body and intake air bypassing the throttle valve is directed to
the IAC valve through a passage.
In this way the intake air volume bypassing the throttle valve is
regulated, controlling the engine speed.
The ECM operates only the IAC valve to perform idle−up and
provide feedback for the target idling speed.
DTC No.DTC Detecting ConditionTrouble Area
P0505Idle speed continues to vary greatly from the target speed
(2 trip detection logic)
IAC valve is stuck or closed
Open or short in IAC valve circuit
Open or short IAC signal circuit
Air intake (hose loose)
DI400−01