TOYOTA TERCEL 1996 Service Repair Manual

- DIAGNOSTICSENGINE
DI-37
1996 TERCEL (RM440U)
DTC P0121 Throttle/Pedal Position Sensor/Switch ºAº
Circuit Range/Performance Problem
CIRCUIT DESCRIPTION
Refer to DTC P0120 on page DI-32.
DTC No.DTC Detection ConditionTrouble Area
P0121
While the vehicle speed drops from 30 km/h (19 mph)
or more to 0 km/h (0 mph), the output value of the
throttle position sensor is out of the applicable range
(2 trip detection logic)

Throttle position sensor
INSPECTION PROCEDURE
1 Are there any other codes (besides DTC P0121) being output?
YES Go to relevant DTC chart.
NO
Replace throttle position sensor.
DI1E9-06

P19660 FI17210A00855
Atmosphere
Housing
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platinum Electrode
Coating (Ceramic)
Exhaust Gas
CoverIdeal Air-Fuel Mixture
Output Voltage
Richer - Air Fuel Ratio - Leaner
DI-38
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
DTC P0125 Insufficient Coolant Temp. for Closed Loop
Fuel Control
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way cata-
lytic converter is used, but for the most efficient use of the three-way catalytic converter, the air-fuel ratio
must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio.
The heated oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity
of the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the ex-
haust gas and provide feedback to the computer for control of the air-fuel ratio.
When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen
sensor informs the ECM of the LEAN condition (small electromotive force: 0 V).
When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the ex-
haust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive
force: 1 V).
The ECM judges by the electromotive force from the oxygen sensor whether the air-fuel ratio is RICH or
LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor causes out-
put of abnormal electromotive force, the ECM is unable to perform accurate air-fuel ratio control.
DTC No.DTC Detection ConditionTrouble Area
P0125
After the engine is warmed up, oxygen sensor output does
not indicate RICH even once when conditions (a), (b) and
(c) continue for at least 1.5 minutes:
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40 - 100 km/h (25 - 62 mph)
(c) Throttle valve does not fully closed

Open or short in oxygen sensor circuit

Oxygen sensor
HINT:
After confirming DTC P0125, use the OBD II scan tool or TOYOTA hand-held tester to confirm voltage output
of the heated oxygen sensor from the CURRENT DATA. If voltage output of the heated oxygen sensor is
0 V, heated oxygen sensor circuit may be open or short.
DI1EA-08

A15693
- DIAGNOSTICSENGINE
DI-39
1996 TERCEL (RM440U)
WIRING DIAGRAM
INSPECTION PROCEDURE
1 Connect OBD II scan tool or TOYOTA hand-held tester and read value for volt-
age output of heated oxygen sensor.
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(c) Warm up the engine to the normal operating temperature.
CHECK:
Read the voltage output of the heated oxygen sensor (bank 1 sensor 1) when the engine is suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 times using accelerator pedal.
OK:
Heated oxygen sensor output a RICH signal (0.45 V or more) at least once.
OK Check and replace ECM (See page IN-26).
NG
2 Check for open and short in harness and connector between ECM and oxygen
sensor (See page IN-26).
NG Repair or replace harness or connector.

DI-40
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
OK
Replace oxygen sensor.

FI7130
Vehicle Speed
50 - 65 km/h
(31 - 40 mph)
Idling
IG SW OFF
1 - 3 min.
1 min.
Time
(1) (2)
(3)(4)
(5)
- DIAGNOSTICSENGINE
DI-41
1996 TERCEL (RM440U)
DTC P0130 Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 1)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI-38.
DTC No.DTC Detection ConditionTrouble Area
P0130
Voltage output of oxygen sensor remains at 0.4 V or
more, or 0.55 V or less, during idling after the engine is
warmed up (2 trip detection logic)
Oxygen sensor

Fuel trim malfunction
HINT:
Sensor 1 refers to the sensor closer to the engine body.
The oxygen sensor's output voltage and the short-term fuel trim value can be read using the OBD II scan
tool or TOYOTA hand-held tester.
WIRING DIAGRAM
Refer to page DI-38.
CONFIRMATION DRIVING PATTERN
(1) Connect the TOYOTA hand-held tester to the DLC3.
(2) Switch the TOYOTA hand-held tester from normal mode to check mode (See page DI-3).
(3) Start the engine and warm it up with all accessory switches OFF.
(4) Drive the vehicle at 50 - 65 km/h (31 - 40 mph) for 1 - 3 minutes to warm up the oxygen sensor.
(5) Idle the engine for 1 minute.
HINT:
If a malfunction exists, the MIL will light up during step (5).
NOTICE:
If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
If you do not have a TOYOTA hand-held tester, turn the ignition switch OFF after performing steps
(3) to (5), then perform steps (3) to (5) again.
DI1EB-08

DI-42
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
INSPECTION PROCEDURE
1 Check for open and short in harness and connector between ECM and oxygen
sensor (See page IN-26).
NG Repair or replace harness or connector.
OK
2 Check for oxygen sensor data.
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(c) 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 0.4 V or more)Changes at about -20 %
3Except 1 and 2
1, 2 Check fuel trim system (See page DI-49).
3

P18349
- DIAGNOSTICSENGINE
DI-43
1996 TERCEL (RM440U)
3 Check output voltage of oxygen sensor during idling.
PREPARATION:
Warm up the oxygen sensor with the engine at 2,500 rpm for approximately 90 seconds.
CHECK:
Using the OBD II scan tool or TOYOTA hand-held tester, read the output voltage of the oxygen sensor during
idling.
OK:
Oxygen sensor output voltage:
Alternates repeatedly between approx. 0.4 V and approx. 0.55 V (See these table):
OK Perform confirmation driving pattern.
(See page DI-41)
NG
Replace oxygen sensor.

DI-44
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
DTC P0133 Oxygen Sensor Circuit Slow Response
(Bank 1 Sensor 1)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI-38 .
DTC No.DTC Detection ConditionTrouble Area
P0133
Response time for oxygen sensor's voltage output to
change from rich to lean, or from lean to rich, is 1 sec. or
more during idling after the engine is warmed up
(2 trip detection logic)

Oxygen sensor
HINT:
Sensor 1 refers to the sensor closer to the engine body.
INSPECTION PROCEDURE
1 Are there any other codes (besides DTC P0133) being output?
YES Go to relevant DTC chart.
NO
Replace oxygen sensor.
DI1EC-07

- DIAGNOSTICSENGINE
DI-45
1996 TERCEL (RM440U)
DTC P0136 Heated Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI-38.
DTC No.DTC Detection ConditionTrouble Area
P0136
Voltage output of the heated oxygen sensor (bank 1 sensor 2)
remains at 0.4 V or more, or 0.5 V or less when the vehicle is
driven at 50 km/h (31 mph) or more after the engine is warmed
up
(2 trip detection logic).

Heated oxygen sensor
HINT:
Sensor 2 refers to the sensor farther away from the engine body.
WIRING DIAGRAM
Refer to page DI-38.
INSPECTION PROCEDURE
1 Are there any other codes (besides DTC P0136) being output?
YES Go to relevant DTC chart.
NO
2 Check for open and short in harness and connector between ECM and heated
oxygen sensor (See page IN-26).
NG Repair or replace harness or connector.
OK
DI00Y-21

DI-46
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
3 Check output voltage of heated oxygen sensor (bank 1 sensor 2).
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(c) After warming up the engine, race the engine at 2,500 rpm for 3 minutes.
CHECK:
Read the output voltage of the heated oxygen sensor (bank 1 sensor 2) when racing the engine after 3 min-
utes have elapsed.
OK:
Heated oxygen sensor output voltage: Alternates from 0.4 V or less to 0.5 V or more.
OK Check that each connector is properly
connected.
NG
Replace heated oxygen sensor.