1996 TOYOTA TERCEL Service Repair Manual

A15727
DI-90
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
DTC P1500 Starter Signal Circuit Malfunction
CIRCUIT DESCRIPTION
When the engine is cranked, the intake air flow is slow, so fuel vaporization is poor. A rich mixture is therefore
necessary in order to achieve good startability. While the engine is being cranked, the battery voltage is ap-
plied to terminal STA of the ECM. The starter signal is mainly used to increase the fuel injection volume for
the starting injection control and after-start injection control.
DTC No.DTC Detection ConditionTrouble Area
P1500No starter signal to ECM

Open or short in starter signal circuit

Open or short in ignition switch or starter relay circuit

ECM
HINT:
In this circuit, diagnosis can only be made in the check mode.
WIRING DIAGRAM
DI95S-01

- DIAGNOSTICSENGINE
DI-91
1996 TERCEL (RM440U)
INSPECTION PROCEDURE
HINT:
This diagnostic chart is based on the premise that the engine is cranked normally. If the engine is not
cranked, proceed to the problem symptoms table on page DI-19.
1 Connect TOYOTA hand-held tester, and check STA signal.
PREPARATION:
(a) Connect the TOYOTA hand-held tester to the DLC3.
(b) Turn the ignition switch ON and push the TOYOTA hand-held tester main switch ON.
CHECK:
Read the STA signal on the TOYOTA hand-held tester while the starter operates.
OK:
Ignition Switch PositionONSTART
STA SignalOFFON
OK Proceed to next circuit inspection shown on
problem symptoms table (See page DI-19).
NG
2 Check for open in harness and connector between ECM and starter relay (See
page IN-26).
NG Repair or replace or connector.
OK
Check and replace ECM.

A15728
A15729
DI-92
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
DTC P1600 ECM BATT Malfunction
CIRCUIT DESCRIPTION
Battery positive voltage is supplied to terminal BATT of the ECM even when the ignition switch is OFF for
use by the DTC memory and air-fuel ratio adaptive control value memory, etc.
DTC No.DTC Detection ConditionTrouble Area
P1600Open in back up power source circuit
Open in back up power source circuit

ECM
HINT:
If DTC P1600 appear, the ECM does not store another DTC.
WIRING DIAGRAM
INSPECTION PROCEDURE
1 Check voltage between terminal BATT of ECM connector and body ground.
PREPARATION:
Remove the lower finish panel.
CHECK:
Measure the voltage between terminal BATT of the ECM con-
nector and the body ground.
OK:
Voltage: 9 - 14 V
OK Check and replace ECM (See page IN-26).
NG
DI01I-24

P20272A04988
Engine Room R/B
EFI Fuse
- DIAGNOSTICSENGINE
DI-93
1996 TERCEL (RM440U)
2 Check EFI fuse.
PREPARATION:
Remove the EFI fuse from the engine room R/B.
CHECK:
Check the continuity of the EFI fuse.
OK:
Continuity
NG Check for short in all harness and components
connected to EFI fuse.
OK
Check and repair harness or connector
between battery, EFI fuse and ECM

DI-94
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
DTC P1780 Park/Neutral Position Switch Malfunction
CIRCUIT DESCRIPTION
The park/neutral position switch goes on when the shift lever is in the N or P shift position. When it goes on
terminal NSW of the ECM is grounded to body ground via the starter relay thus the terminal NSW voltage
becomes 0 V. When the shift lever is in the D, 2, L or R position, the park/neutral position switch goes off,
so the voltage of ECM terminal NSW becomes battery positive voltage, the voltage of the ECM internal pow-
er source.
If the shift lever is moved from the N position to the D position, this signal is used for air-fuel ratio correction
and for idle speed control (estimated control), etc.
DTC No.DTC Detection ConditionTrouble Area
P1780
When driving under conditions (a) and (b) for 30 seconds or
more, the park/neutral position switch is ON (N position)
(2 trip detection logic)
(a) Vehicle speed: 80 km/h (50 mph) or more
(b) Engine speed: 2,000 - 3,000 rpm

Short in park/neutral position switch circuit

Park/neutral position switch

ECM
HINT:

After confirming DTC P1780, use the TOYOTA hand-held tester to confirm the PNP switch signal from
the CURRENT DATA.

After confirming DTC P1780, in the case that the diagnostic trouble codes are erased by disconnecting
the battery terminals or EFI fuse, after operating the shift lever few times from P or N position to D posi-
tion, confirm the PNP switch signal using the CURRENT DATA of the TOYOTA hand-held tester. If
the PNP switch signal is not displayed on TOYOTA hand-held tester, the circuit of PNP switch signal
may be short.
DI3A1-04

A15731
P24793
- DIAGNOSTICSENGINE
DI-95
1996 TERCEL (RM440U)
WIRING DIAGRAM
INSPECTION PROCEDURE
1 Check park/neutral position switch.
PREPARATION:
Disconnect the park/neutral position switch connector.
CHECK:
Check continuity between each terminal shown below when the
shift lever is positioned to each range.
OK:
Shift PositionTerminal No. to continuity
P4 - 75 - 6
R4 - 8-
N4 - 105 - 6
D4 - 9-
22 - 4-
L3 - 4-

A15733
DI-96
- DIAGNOSTICSENGINE
1996 TERCEL (RM440U)
NG Replace park/neutral position switch.
OK
2 Check voltage between terminal NSW 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 NSW of the ECM con-
nector and the body ground after the shift lever is moved to the
following positions.
Shift lever positionP or NL, 2, D or R
Voltage0 - 3 V9 - 14 V
OK Check and replace ECM (See page IN-26).
NG
Check for open and short in harness and con-
nector between ECM and park/neutral posi-
tion switch (See page IN-26).

A15734
- DIAGNOSTICSENGINE
DI-97
1996 TERCEL (RM440U)
ECM Power Source Circuit
CIRCUIT DESCRIPTION
When the ignition switch is turned ON, battery positive voltage is applied to the coil, closing the contacts of
the EFI main relay and supplying power to the terminal +B of the ECM.
WIRING DIAGRAM
DI4LL-02