TOYOTA TERCEL 1996 Service Repair Manual

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

- DIAGNOSTICSENGINE
DI-51
1996 TERCEL (RM440U)
4 Check injector injection (See page MF-19).
NG Replace injector.
OK
5 Check manifold absolute pressure sensor and engine coolant temp. sensor
(See page DI-20, DI-28).
NG Repair or replace.
OK
6 Check for spark and ignition (See page IG-1).
NG Repair or replace.
OK
Check and replace ECM (See page IN-26).

DI-52
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
DTC P0300 Random/Multiple Cylinder Misfire Detected
DTC P0301 Cylinder 1 Misfire Detected
DTC P0302 Cylinder 2 Misfire Detected
DTC P0303 Cylinder 3 Misfire Detected
DTC P0304 Cylinder 4 Misfire Detected
CIRCUIT DESCRIPTION
Misfire: The ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in
the crankshaft rotation for each cylinder.
The ECM counts the number of times the engine speed change rate indicates that misfire has occurred. And
when the misfire rate equals or exceeds the count indicating that the engine condition has deteriorated, the
MIL lights up.
If the misfire rate is high enough and the driving conditions will cause catalyst overheating, the MIL blinks
when misfiring occurs.
DTC No.DTC Detection ConditionTrouble Area
P0300Misfiring of random cylinders is detected during any particular
200 or 1,000 revolutions
Ignition system


Injector
P0301
P0302
For any particular 200 revolutions of the engine, misfiring is
detected which can cause catalyst overheating
(This causes MIL to blink)

Injector

Fuel line pressure

Compression pressure

Valve clearance not to specification
P0302
P0303
P0304For any particular 1,000 revolutions of the engine, misfiring is
detected which causes a deterioration in emissions
(2 trip detection logic)
Valve clearance not to s ecification

Valve timing

Manifold absolute pressure sensor

Engine coolant temp. sensor
HINT:
When the 2 or more codes for a misfiring cylinder are recorded repeatedly but no Random Misfire code is
recorded, it indicates that the misfires were detected and recorded at different times.
DI39Y-04

A15696
FI6588
FI6538
A00064
10V/
Division
GND
100 m sec./Division (Idling)GND(Magnification)
1 m sec./Division (Idling)
Injection duration10V/
Division
- DIAGNOSTICSENGINE
DI-53
1996 TERCEL (RM440U)
WIRING DIAGRAM
Reference: INSPECTION USING OSCILLOSCOPE
INJECTOR SIGNAL WAVEFORM
With the engine idling, measure between terminals #10, #20 and E01 of ECM.
HINT:
The correct waveform is as shown.

P25779S00553A05593
DI-54
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
INSPECTION PROCEDURE
1 Check spark plug and spark of misfiring cylinder.
PREPARATION:
(a) Disconnect the high-tension cord or ignition coil.
(b) Remove the spark plug.
CHECK:
(a) Check plug type.
(b) Check for carbon deposits on electrode.
(c) Check electrode gap.
OK:
(1) Twin ground electrodes type.
Recommended spark plug:
ND: K16TR11
NGK: BKR5EKB-11
(2) No large carbon deposit present.
Not wet with gasoline or oil.
(3) Electrode gap: 1.0 - 1.1 mm (0.039 - 0.043 in.)
PREPARATION:
(a) Install the spark plug to the high-tension cord or ignition
coil.
(b) Disconnect the injector connector.
(c) Ground the spark plug.
CHECK:
Check if spark occurs while engine is being cracked.
NOTICE:
To prevent excess fuel being injected from the injectors
during this test, do not crank the engine for more than 5 -
10 seconds at a time.
OK:
Spark jumps across electrode gap.
NG Replace or check ignition system (See page
IG-1).
OK

A15699
- DIAGNOSTICSENGINE
DI-55
1996 TERCEL (RM440U)
2 Check voltage of ECM terminals for injector of failed cylinder.
PREPARATION:
(a) Remove the lower finish panel.
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between applicable terminals of the ECM
connector and the body ground.
OK:
Voltage: 9 - 14 V
OK Go to step 4.
NG
3 Check injector resistance of misfiring cylinder (See page MF-16).
NG Replace injector.
OK
Check for open and short in harness and con-
nector between injector and ECM (See page
IN-26).
4 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
5 Check injector injection (See page MF-16).
NG Replace injector.

DI-56
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
OK
6 Check EGR system (See page EC-8).
NG Replace injector.
OK
7 Check manifold absolute pressure sensor and engine coolant temp. sensor (See
page DI-41 and DI-45).
NG Repair or replace.
OK
Check compression pressure (See page EM-3), valve clearance (See page EM-4) and valve tim-
ing (See page EM-17).