2001 TOYOTA PRIUS Service Repair Manual

A14052
ECM
G±R
7
236 1B1AIA2 12
BR
G±Y 1
1 EFI2
1 5
11
1 1
12
3 Engine Room J/B
B±GF12
MAINFL
Block
No. 2
BatteryJ1
J/C W±B4
B
P±L
Y12
2
4 3
A
IEB
IP1BR
J23 BR
H9
Bank 1
Sensor 22
1 4
3
18
E10
E10E2 MREL
E11
BR IE1
IE1
IE1 W
W
D
11 2225
16
7 (Shielded) (Shielded)(Shielded) 2
FL Block No. 1
F13
J7
J/CJ4
J/C
J/C
A
ACHT1A
OX1B E10E10 E10E8E9
OX1A
HT1B G±R
EFI
Relay
1K 1F
1F
C
B
J23 J22 J23E
E EBR BR IK1
IK1
IK1 W (Shielded)P±L
P±L H3
Bank 1
Sensor 1
B
B
W±B 3
13
12
± DIAGNOSTICSENGINE
DI±45
2001 PRIUS (RM778U)
HINT:
After confirming DTC P0125, use the OBD II scan tool or TOYOTA hand-held tester to confirm voltage output
of oxygen sensor (bank 1 sensor 1) from "CURRENT DATA".
If voltage output of oxygen sensor (bank 1 sensor 1) is less than 0.1 V, oxygen sensor (bank 1 sensor 1) circuit
may be open or short.
WIRING DIAGRAM

DI±46
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
HINT:

If the vehicle run out of fuel, the air±fuel ratio is LEAN and DTC P0125 will be recorded .
The MIL then comes on.

Read freeze frame data using TOYOTA hand±held tester or OBD II scan tool. Because freeze frame
records the engine conditions when the malfunction is detected, when troubleshooting it is useful for
determining whether the vehicle was running or stopped, the engine warmed up or not, the air±fuel
ratio lean or rich, etc at the time of the malfunction.

There is a possibility that P0125 is detected because of abnormal fuel system, so, when P0125 is mem-
orized, check P0171 and P0172 even if P0171 and P0172 are memorized.
1 Are there any other codes (besides DTC P0125) being output ?
YES Go to relevant DTC chart.
NO
2 Connect the OBD II scan tool or TOYOTA hand±held tester and read value for
voltage output of oxygen sensor (bank 1 sensor 1).
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(b) Warm up engine to normal operating temp (above 75°C).
CHECK:
Read voltage output of the oxygen sensor (bank 1 sensor 1) when engine is suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 times using accelerator pedal.
OK:
Both oxygen sensor (bank 1 sensor 1) output a RICH signal (0.45 V or more) at least once.
OK Go to step 9.
NG
3 Check for open and short in harness and connector between ECM and oxygen
sensor (bank 1 sensor 1) (See page IN±41).
NG Repair or replace harness or connector.
OK

± DIAGNOSTICSENGINE
DI±47
2001 PRIUS (RM778U)
4 Check whether misfire is occurred or not by monitoring DTC and data list.
NG Perform troubleshooting for misfire (See page
DI±65).
OK
5 Check air induction system (See page SF±1).
NG Repair or replace induction system.
OK
6 Check fuel pressure (See page SF±6).
NG Check and repair fuel pump and fuel pipe line
(See page SF±1).
OK
7 Check injector injection (See page SF±12).
NG Replace injector.
OK
8 Check gas leakade on exhaust system.
NG Repair or replace.
OK

DI±48
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
Replace oxygen sensor (bank 1 sensor 1).
9 Perform confirmation driving pattern (See page DI±50).
Go
10 Is there DTC P0125 being output again?
YES Check and replace ECM.
NO
11 Did vehicle runs out of fuel in the past?
NO Check for intermittent problems
(See page DI±3).
YES
DTC P0125 is caused by running out of fuel.