ECM TOYOTA TERCEL 1996 Service Owner's Guide

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

- 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

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-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.

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.

A15700
- DIAGNOSTICSENGINE
DI-57
1996 TERCEL (RM440U)
DTC P0325 Knock Sensor 1 Circuit Malfunction
CIRCUIT DESCRIPTION
A knock sensor is fitted to the cylinder block to detect engine knocking. This sensor contains a piezoelectric
element which generates a voltage when it becomes deformed, which occurs when the cylinder block vi-
brates due to knocking. If engine knocking occurs, ignition timing is retarded to suppress it.
DTC No.DTC Detection ConditionTrouble Area
P0325
No knock sensor 1 signal to ECM with engine speed 1,200 rpm
or more
(2 trip detection logic)
Open or short in knock sensor 1 circuit

Knock sensor 1 (looseness)

ECM
If the ECM detects the above diagnosis conditions, it operates the fail-safe function in which the corrective
retard angle value is set to the maximum value.
WIRING DIAGRAM
DI012-20

A15701
DI-58
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
INSPECTION PROCEDURE
1 Check continuity between terminal KNK of ECM connector and body ground.
PREPARATION:
(a) Remove the lower finish panel.
(b) Disconnect the E7 connector of ECM.
CHECK:
Measure the resistance between terminal KNK of the ECM con-
nector and the body ground.
OK:
Resistance: 1 MW or higher
OK Go to step 3.
2 Check knock sensor (See page MF-50).
NG Replace knock sensor.
OK
3 Check for open and short in harness and connector between ECM and knock
sensor (See page IN-26).
NG Repair or replace harness or connector.
OK
4 Does malfunction disappear when a good knock sensor is installed?
YES Replace knock sensor.
NO
Check and replace ECM (See page IN-26).