engine coolant TOYOTA TERCEL 1996 Service User Guide

DI-14
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)DTC No.
(See Page)
Detection ItemTrouble AreaMIL*Memory
P0171
(DI-49)System too Lean
(Fuel Trim)
Air intake (hose loose)
Fuel line pressure
Injector blockage
Oxygen sensor malfunction
Manifold absolute pressure sensor
Engine coolant temp. sensor

P0172
(DI-49)System too Rich
(Fuel Trim)
Fuel line pressure
Injector blockage, leak
Oxygen sensor malfunction
Manifold absolute pressure sensor
Engine coolant temp. sensor

P0300
(DI-52)Random/Multiple Cylinder
Misfire DetectedIgnition system
Injector
FlliP0301
P0302
P0303
P0304
(DI-52)Misfire Detected
- Cylinder 1
- Cylinder 2
- Cylinder 3
- Cylinder 4Fuel line pressure
Compression pressure
Valve clearance not to specification
Valve timing
Manifold absolute pressure sensor
Engine coolant temp. sensor

P0325
(DI-57)Knock Sensor 1 Circuit
MalfunctionOpen or short in knock sensor 1 circuit
Knock sensor 1 (looseness)
ECM

P0335
(DI-60)Crankshaft Position Sensor
Circuit ºAº Malfunction
Open or short in crankshaft position sensor circuit
Crankshaft position sensor
Starter
ECM

P0340
(DI-63)Camshaft Position Sensor
Circuit Malfunction
Open or short in camshaft position sensor circuit
Camshaft position sensor
Starter
ECM

P0420
(DI-73)Catalyst System Efficiency
Below ThresholdThree-way catalytic converter
Open or short in (heated) oxygen sensor circuit
(Heated) oxygen sensor

P0500
(DI-76)Vehicle Speed Sensor
Malfunction
Open or short in vehicle speed sensor circuit
Vehicle speed sensor
Speedometer cable
ECM

P0505
(DI-78)Idle Control System
Malfunction
IAC valve is stuck or closed
Open or short in IAC valve circuit
Open or short in AC1 switch circuit
Air intake (hose loose)

*: 


MIL lights up

DI4LH-02
P19551
ECM TerminalsE7 E6
1 2 3 4 5 6 7 8 9 10 11 12 13
23 24 25 26 1920 21 22 18 1415 16 171 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16
- DIAGNOSTICSENGINE
DI-17
1996 TERCEL (RM440U)
TERMINALS OF ECM
Symbols (Terminals No.)Wiring ColorConditionSTD Voltage (V)
BATT (E6-2) - E1 (E7-24)W-R - BRAlways9 - 14
+B (E6-9) - E1 (E7-24)B-R - BRIG switch ON9 - 14
VC (E7-18) - E2 (E7-16)LG-R - BRIG switch ON4.5 - 5.5
VTA (E7 19) E2 (E7 16)YG BR
IG switch ON
Throttle valve fully closed0.3 - 1.0
VTA (E7-19) - E2 (E7-16)Y-G - BRIG switch ON
Throttle valve fully open3.2 - 4.9
PIM (E7 4) E2 (E7 16)PBRIG switch ON3.3 - 3.9PIM (E7-4) - E2 (E7-16)P - BRApply vacuum 26.7 kPa (200 mmHg, 7.9 in.Hg)2.5 - 3.1
THA (E7-15) - E2 (E7-16)L-B - BRIdling, Intake air temp. 20°C (68° F)0.5 - 3.4
THW (E7-3) - E2 (E7-16)G-B - BRIdling, Engine coolant temp. 80°C (176°F) 0.2 - 1.0
STA (E7-11) - E1 (E7-24)B-W - BRCranking6.0 or more
IG switch ON9 - 14
#10 (E7-12) - E01 (E7-13)G - BRIdlingPulse generation
(See page DI-52)
IG switch ON9 - 14
#20 (E7-11) - E01 (E7-13)Y - BRIdlingPulse generation
(See page DI-52)
IG switch ON9 - 14
#30 (E7-25) - E01 (E7-13)R - BRIdlingPulse generation
(See page DI-52)
IG switch ON9 - 14
#40 (E7-24) - E01 (E7-13)L - BRIdlingPulse generation
(See page DI-52)
IGT1 (E7-6) - E1 (E7-24)LG - BRIdlingPulse generation
(See page DI-84)
IGT2 (E7-5) - E1 (E7-24)L-Y - BRIdlingPulse generation
(See page DI-84)
IG switch ON, Disconnect igniter connector4.5 - 5.5
IGF (E7-7) - E1 (E7-24)LG-B - BRIdlingPulse generation
(See page DI-84)
G2(E7-20) - NE- (E7-9)R - WIdlingPulse generation
(See page DI-60)
NE(E7-21) - NE- (E7-9)B - WIdlingPulse generation
(See page DI-60)
FC (E6-4) - E1 (E7-24)G-B - BRIG switch ON9 - 14

A10940
ECM
E7
E7 G-B
BR5V
E1 E2 THW
2
1 Engine Coolant Temp. Sensor
3
16 DI-28
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
DTC P0115 Engine Coolant Temp. Circuit Malfunction
CIRCUIT DESCRIPTION
A thermistor built into the engine coolant temperature sensor changes the resistance value according to the
engine coolant temperature. The structure of the sensor and connection to the ECM is the same as in the
intake air temp. circuit malfunction shown on page DI-24.
If the ECM detects the DTC P0115, it operates the fail-safe function in which the engine coolant temp. is
assumed to be 80°C (176°F).
DTC No.DTC Detection ConditionTrouble Area
P0115Open or short in engine coolant temp. sensor circuit

Open or short in engine coolant temp. sensor circuit

Engine coolant temp. sensor

ECM
HINT:
After confirming DTC P0115, use the OBD II scan tool or TOYOTA hand-held tester to confirm the engine
coolant temperature from the CURRENT DATA.
Temperature DisplayedMalfunction
-40°C (-40°F)Open circuit
140°C (284°F) or moreShort circuit
WIRING DIAGRAM
DI1E6-08

A15685
- DIAGNOSTICSENGINE
DI-29
1996 TERCEL (RM440U)
INSPECTION PROCEDURE
HINT:
If DTC P0105, P0106, P0110, P0115, P0120 are output simultaneously, E2 (sensor ground) may be open.
1 Connect OBD II scan tool or TOYOTA hand-held tester, and read value of engine
coolant temperature.
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) Turn the ignition switch ON and OBD II scan tool or TOYOTA hand-held tester main switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA hand-held tester.
OK:
Same value as the actual engine coolant temperature
HINT:

If there is open circuit, OBD II scan tool or TOYOTA hand-held tester indicates -40°C (-40°F).

If there is short circuit, OBD II scan tool or TOYOTA hand-held tester indicates 140°C (284°F) or more.
NG -40°C (-40°F) ... Go to step 2.
140°C (284°F) or more ... Go to step 4.
OK
Check for intermittent problems (See page
DI-3).
2 Check for open in harness or ECM.
PREPARATION:
(a) Disconnect the engine coolant temp. sensor connector.
(b) Connect sensor wire harness terminals together.
(c) Turn the ignition switch ON.
CHECK:
Read the temperature value on the OBD II scan tool or TOYO-
TA hand-held tester.
OK:
Temperature value: 140°C (284°F) or more
OK Confirm good connection at sensor. If OK, re-
place engine coolant temp. sensor
NG

A15686
A15687
DI-30
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
3 Check for open in harness or ECM.
PREPARATION:
(a) Remove the lower finish panel.
(b) Connect terminals THW and E2 of ECM connector to-
gether.
HINT:
Engine coolant temperature sensor connector is disconnected.
Before checking, do a visual and contact pressure check for the
ECM connector (See page IN-26).
(c) Turn the ignition switch ON.
CHECK:
Read the temperature value on the OBD II scan tool or TOYO-
TA hand-held tester.
OK:
Temperature value: 140°C (284°F) or more
OK Open in harness between terminal E2 or termi-
nal THW, repair or replace harness.
NG
Confirm good connection at ECM.
If OK, replace ECM.
4 Check for short in harness and ECM.
PREPARATION:
(a) Disconnect the engine coolant temperature sensor con-
nector.
(b) Turn the ignition switch ON.
CHECK:
Read the temperature value on the OBD II scan tool or TOYO-
TA hand-held tester.
OK:
Temperature value: -40°C (-40°F)
OK Replace engine coolant temperature sensor.
NG

A15688
- DIAGNOSTICSENGINE
DI-31
1996 TERCEL (RM440U)
5 Check for short in harness or ECM.
PREPARATION:
(a) Remove the lower finish panel.
(b) Disconnect the E7 connector of ECM.
HINT:
The engine coolant temperature sensor connector is discon-
nected.
(c) Turn the ignition switch ON.
CHECK:
Read the temperature value on the OBD II scan tool or TOYO-
TA hand-held tester.
OK:
Temperature value: -40°C (-40°F)
OK Repair or replace harness or connector.
NG
Check and replace ECM (See page IN-26).

DI-32
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
DTC P0116 Engine Coolant Temp. Circuit Range/
Performance Problem
CIRCUIT DESCRIPTION
Refer to Engine Coolant Temp. Circuit Malfunction on page DI-28.
DTC No.DTC Detection ConditionTrouble Area
P0116
20 min. or more after the engine starts, engine coolant
temp. sensor value is 40°C (104°F) or less (2 trip detection
logic)
Engine coolant temp. sensor

Cooling system
INSPECTION PROCEDURE
HINT:
If DTC P0115 and P0116 are output Simultaneously, engine coolant temperature sensor circuit may be open.
Perform troubleshooting of DTC P0115 first.
1 Are there any other codes (besides DTC P0116) being output?
YES Go to relevant DTC chart.
NO
2 Check thermostat (See page CO-10).
NG Replace thermostat.
OK
Replace engine coolant temp. sensor.
DI1E7-08

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

- 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

- 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).