TOYOTA CAMRY 1999 Service Repair Manual

DI±50
± DIAGNOSTICSENGINE

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.

OBD II scan tool (excluding TOYOTA hand±held tester) displays the one fifth of the A/F sensor output
voltage which is displayed on the TOYOTA hand±held tester.
WIRING DIAGRAM
Refer to DTC P0125 on page DI±40.
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 was warmed up or not, the airÅfuel ratio was lean
or rich, etc. at the time of the malfunction.
1 Check air induction system (See Pub. No. RM654U, page SF±1).
NG Repair or replace.
OK
2 Check injector injection (See Pub. No. RM654U, page SF-23).
NG Replace injector.
OK
3 Check manifold absolute pressure sensor (See Pub. No. RM654U, page SF±53)
and engine coolant temperature sensor (See Pub. No. RM654U, page SF±49).
NG Repair or replace.
OK
4 Check for spark and ignition (See page IG±1).
NG Repair or replace.

± DIAGNOSTICSENGINE
DI±51
OK
5 Check fuel shutoff valve operation (See page DI±86).
NG Replace or repair.
OK
6 Check gas leakage on exhaust system.
NG Repair or replace.
OK
Check and replace ECM (See page IN±29).
7 Check output voltage of A/F sensor (bank 1 sensor 1).
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(b) Warm up the A/F sensor with the engine speed at 2,500 rpm for approx. 90 sec.
CHECK:
Read the voltage value of the A/F sensor on the screen of OBD II scan tool or TOYOTA hand±held tester
when you perform all the following conditions.
HINT:
The voltage of the AF+ terminal of the ECM is 3.3 V fixed and the AF± terminal is 3.0 V fixed. Therefore,
it is impossible to check the A/F sensor output voltage at the terminals (AF+/AF±) of the ECM.
OK:
ConditionA/F Sensor Voltage value
Engine idling
Engine racing
Not remains at 3.30 V (0.660 V*)

Not remains at38V(076V*) or moreDriving at engine speed 1,500 rpm or more and vehicle
speed 40 km/h (25 mph) or more, and operate throttle valve
open and close
Not remains at 3.8 V (0.76 V*) or more

Not remains at 2.8 V (0.56 V*) or less
*: When you use OBD II scan tool (excluding TOYOTA hand±held tester)
HINT:

During fuel enrichment, there is a case that the output voltage of the A/F sensor is below 2.8 V (0.56
V*), it is normal.

DI±52
± DIAGNOSTICSENGINE

During fuel cut, there is a case that the output voltage of the A/F sensor is above 3.8 V (0.76 V*), it
is normally.

If the output voltage of the A/F sensor remains at 3.30 V (0.660 V*) even after performing all the above
conditions, A/F sensor circuit may be open.

If the output voltage of the A/F sensor remains at 4.5 V (0.76 V*) or more, even after performing all
the above conditions, A/F sensor circuit may be short.
*: When you use the OBD II scan tool (excluding TOYOTA hand±held tester).
OK Go to step 9.
NG
8 Check for open and short in harness and connector between ECM and oxygen
sensor (See page IN±29).
NG Repair or replace harness or connector.
OK
Replace A/F sensor.
9 Perform confirmation driving pattern (See page DI±79).
Go
10 Is there DTC P0171 or P0172 being output again?
YES Check and replace ECM (See page IN±29).
NO
11 Did vehicle runs out of fuel in the past?
NO Check for intermittent problems
(See page DI±3).

± DIAGNOSTICSENGINE
DI±53
YES
DTC P0171 or P0172 is caused by running out of fuel.

A09428
(Fig.1)
Acceptable
Resistance kW
± 20 0 20 40 60 80 100
(± 4) (32) (68) (104) (140) (176) (212) 30
20
10
5
3
2
1
0.5
0.3
0.2
0.1
Te m p .°C (F°)
A00310
E7
E56
9ECM
5 V
THCNG2
E2
E1 R
BR 2
1 Fuel Temperature Sensor
for Delivery Pipe
P±B DI±54
± DIAGNOSTICSENGINE
DTC P0180 Fuel Temperature Sensor ºAº Circuit Mal-
function
CIRCUIT DESCRIPTION
The fuel temperature sensor is built into the delivery pipe and
senses the fuel temperature.
A thermistor built in the sensor changes the resistance value
according to the fuel temperature, the lower the fuel tempera-
ture, the greater the thermistor resistance value, and the higher
the fuel temperature, the lower the thermistor resistance value
(See Fig.1).
The fuel temperature sensor is connected to the ECM (See be-
low). The 5 V power source voltage in the ECM is applied to the
fuel temperature sensor from terminal THCNG2 via a resistor
R.
That is, resistor R and the fuel temperature sensor are con-
nected in series. When the resistance value of the fuel tempera-
ture sensor changes in accordance with changes in the fuel
temperature, the potential at terminal THCNG2 also changes.
Based on this signal, the ECM increases the fuel injection vol-
ume to improve driveability during cold engine operation.
If the ECM detects the DTC P0180, it operates the fail safe func-
tion in which the fuel temperature is assumed to be 20°C
(68°F).
DTC No.DTC Detecting ConditionTrouble Area
P0180Open or short in fuel temperature sensor circuit

Open or short in fuel temperature sensor circuit for delivery
pipe

Fuel temperature sensor for delivery pipe

ECM
HINT:
After confirming DTC P0180, use the OBD II scan tool or TOYOTA hand±held tester to confirm the fuel tem-
perature from the CURRENT DATA.
WIRING DIAGRAM
DI64U±01

A09295BE6653
A09298
E2
ON
THCNG2
(±) (+)
± DIAGNOSTICSENGINE
DI±55
INSPECTION PROCEDURE
HINT:
If DTCs P0105, P0106, P0110, P0115, P0120, P0180 and P0190 are output simultaneously, E2 (sensor
ground) may be open.
1 Check voltage between terminals THCNG2 and E2 of engine ECU connector.
PREPARATION:
(a) Remove the glove compartment.
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals THCNG2 and E2 of the
ECM connector.
Temperature °C (°F)Voltage V
±20 (±40)0.66 ± 0.78
20 (68)2.5 ± 2.75
80 (176)4.42 ± 4.52
OK:
OK Check for intermittent problem (See page
DI±3).
NG
2 Check fuel temperature sensor for delivery pipe (See page SF±42).
NG Replace.
OK
3 Check for open and short in harness and connector between engine ECU and
fuel temperature sensor for delivery pipe (See page IN±29).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page SF±42).

A00309
ECM Fuel Pressure Sensor
for Delivery Pipe
1PCNG2VC
E2 Y
G±BE5
E7
E5 3
25 V
E1 1
5
9
BR DI±56
± DIAGNOSTICSENGINE
DTC P0190 Fuel Rail Pressure Circuit Malfunction
CIRCUIT DESCRIPTION
By a built±in sensor unit, the fuel rail pressure sensor detects the intake manifold pressure as a voltage. The
ECM then determines the basic injection duration and basic injection advance angle based on this voltage.
Since the fuel rail pressure sensor does not use the atmospheric pressure as a criterion, but senses the ab-
solute pressure inside the intake manifold (the pressure in proportion to the present absolute vacuum 0),
it is not influenced by fluctuations in the atmospheric pressure due to high altitude and other factors. This
permits it to control the air±fuel ratio at the proper lever under all conditions.
DTC No.DTC Detecting ConditionTrouble Area
P0190Open or short in fuel pressure sensor circuit for delivery pipe

Open or short in fuel pressure sensor circuit for delivery pipe

Fuel pressure sensor for delivery pipe

ECM
HINT:
After confirming DTC P0190, use the OBD II scan tool or TOYOTA hand±held tester to confirm the fuel rail
pressure from the CURRENT DATA.
WIRING DIAGRAM
DI64V±01

BE6653A03008A09254
ON
E2VC
(±)
(+)
A09293BE6653A09297
E2 ONPCNG2
(±) (+)
± DIAGNOSTICSENGINE
DI±57
INSPECTION PROCEDURE
HINT:
If DTC P0105, P0106, P0110, P0115, P0120, P0180 and P0190 are output simultaneously, E2 (sensor
ground) may be open.
1 Check voltage between terminals VC and E2 of ECM connector.
PREPARATION:
(a) Remove the glove compartment (See Pub. No. RM654U,
page SF±64).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals VC and E2 of the ECM
connector.
OK:
Voltage: 4.5 ± 5.5 V
NG Check and replace ECM (See page IN±29).
OK
2 Check voltage between terminals PCNG2 and E2 of ECM connector.
PREPARATION:
(a) Remove the glove compartment.
(b) Start the engine (See Pub. No. RM654U, page SF±64).
CHECK:
Measure the voltage between terminals PCNG2 and E2 of the
ECM connector.
OK:
Voltage: 3.1 ± 3.6 V at 20°C (68°F)
HINT:
The fuel pressure in the delivery pipe is 784 ± 1,078 kPa (8.0
± 11.0 kgf/cm
2, 114 ± 156 psi)
OK Check and replace ECM (See page IN±29).
NG
3 Check for open and short in harness and connector between fuel pressure sen-
sor for delivery pipe and ECM
(See page IN±29).
NG Repair or replace harness or connector.

DI±58
± DIAGNOSTICSENGINE
OK
Replace fuel pressure sensor for delivery
pipe (See page SF±43).

A09394
ECM
G
NE+
NE±
E1 E6
E6
E65
4
17 B±W
L
B±R
L BR Camshaft Position Sensor
Crankshaft Position Sensor1
2
1
2B±R
± DIAGNOSTICSENGINE
DI±59
DTC P0335 Crankshaft Position Sensor ºAº Circuit Mal-
function
CIRCUIT DESCRIPTION
Crankshaft position sensor (NE signal) consists of a magnet, iron and pickup coil.
The NE signal plate has 34 teeth and is installed on the crankshaft timing pulley. The NE signal sensor gener-
ates 34 signals at 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 signal.
DTC No.DTC Detecting ConditionTrouble Area
P0335
No crankshaft position sensor signal to ECM during cranking
(2 trip detection logic)
Open or short in crankshaft position sensor circuit

Crankshaft position sensor
P0335No crankshaft position sensor signal to ECM with engine
speed 600 rpm or more (2 trip detection logic)

Crankshaft osition sensor

Crankshaft timing pulley

ECM
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

Perform troubleshooting of DTC 335 first. If no trouble is found, troubleshoot the following mechanical
system.

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 was warmed up or not, the air±fuel
ratio was lean or rich, etc. at the time of the malfunction.
DI013±12