1996 TOYOTA TERCEL Service Repair Manual

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.

A15695
- DIAGNOSTICSENGINE
DI-47
1996 TERCEL (RM440U)
DTC P0135 Heated Oxygen Sensor Heated Circuit
Malfunction (Bank 1 Sensor 1)
DTC P0141 Heated Oxygen Sensor Heated Circuit
Malfunction (Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI-38.
DTC No.DTC Detection ConditionTrouble Area
P0135
When the heater operates, heater current exceeds 2 A
(2 trip detection logic)
Open or short in heater circuit of heated oxygen sensor
Htd htP0135
P0141Heater current of 0.25 A or less when the heater
operates (2 trip detection logic)
Heated oxygen sensor heater

ECM
WIRING DIAGRAM
Refer to page DI-38.
INSPECTION PROCEDURE
1 Check voltage between terminal HT1, HT2 of ECM connector and body ground.
PREPARATION:
(a) Remove the lower finish panel.
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminal HT1, HT2 of the ECM
connector and the body ground.
OK:
Voltage: 9 - 14 V
OK Check and replace ECM (See page IN-26).
NG
2 Check resistance of heated oxygen sensor heater (See page MF-53).
NG Replace heated oxygen sensor.
OK
DI1ED-1 1

DI-48
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
Check and repair harness or connector be-
tween EFI main relay and heated oxygen sen-
sor and ECM.

- DIAGNOSTICSENGINE
DI-49
1996 TERCEL (RM440U)
DTC P0171 System too Lean (Fuel Trim)
DTC P0172 System too Rich (Fuel Trim)
CIRCUIT DESCRIPTION
ºFuelº 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.
ºShort-term fuel trimº is the short-term fuel compensation used to maintain the air-fuel ratio 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.
ºLong-term fuel trimº is overall fuel compensation carried out long-term to compensate for continual devi-
ation of the short-term fuel trim form 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 Detection ConditionTrouble Area
P0171
When the air-fuel ratio feedback is stable after engine warming
up, the fuel trim is considerably in error on the RICH side
(2 trip detection logic)

Air intake (hose loose)

Fuel line pressure

Injector blockage

Heated oxygen sensor malfunction

Manifold absolute pressure sensor

Engine coolant temp. sensor
P0172
When the air-fuel ratio feedback is stable after engine warming
up, the fuel trim is considerably in error on the LEAN side.
(2 trip detection logic)

Fuel line pressure

Injector blockage, leak

Heated 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 total of the short-term fuel trim value and long-term fuel trim value is within + 25 %, the system
is functioning normally.

If the vehicle runs out of fuel, the air-fuel ratio is LEAN and DTC P0171 is recorded. The MIL then
comes on.
DI052-09

DI-50
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
INSPECTION PROCEDURE
1 Check air induction system (See page MF-1).
NG Repair or replace.
OK
2 Check for heated 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
3 Check for oxygen sensor
(See page DI-41).
1, 2
3 Check fuel pressure (See page MF-1).
NG Check and repair fuel pump, pressure regulator,
fuel pipe line and filter. (See page MF-5)
OK