2001 TOYOTA PRIUS check engine light

ENGINE ± 1NZ-FXE ENGINE 76
Fail Safe
If an abnormal condition occurs with the ETCS-i, the check engine warning light in the combination meter
illuminates to alert the driver. The current to the throttle control motor is cut off to prevent the ETCS-i from
operating. This enables the return spring to close the throttle valve.
Diagnosis
If the diagnostic trouble code 89 is being output to the combination meter check engine warning light, it
means that the ECM has detected a malfunction in the ETCS-i, and outputs the diagnostic trouble code of
the ETCS-i.
Also, the diagnostic trouble code can be output to a hand-held tester via the data link connector 3.
For details, refer to the 2001 Prius Repair Manual (Pub. No.RM778U).

THS (TOYOTA HYBRID SYSTEM)
182TH22
1. READY Light
2. Output Control
Warning Light 3. Master Warning Light
4. Malfunction Indicator light 5. Discharge Warning Light
6. EMPS Malfunction
Warning Light7. HV Battery Warning Light
8. Hybrid System
Malfunction Warning
Light 32
INDICATOR AND WARNING LIGHT
The warning lights of the Prius are different from those on conventional vehicles. Inspection and repair
should be performed while referring to the troubleshooting section in the 2001 Prius repair manual
(RM778U).

Center Meter 
Multi Information Display 
1. READY lightTurns on when the ignition switch is turned to START to indicate that the ve-
hicle is ready to drive.
2. Output control
warning lightTurns on when the remaining HV battery charge becomes insufficient at R
range or when there is an abnormal temperature rise in the HV battery due
to continuous driving under heavy loads. It may also light when the HV bat-
tery temperature is low (after starting at low temperatures). The hybrid sys-
tem output is limited while this light is on.
Travel at reduced speeds (avoid sudden acceleration) while the light is lit.
3. Master warning
lightTurns on with buzzer sounding by linked operation with warning lights ª6º
to ª8º on the multi center display.
4. Malfunction
indicator lightTurns on when there is a malfunction in the engine control system.
5. Discharge warning
lightTurns on when there is a malfunction in the 12 V charging system (converter
assembly).
If it turns on together with the master warning light and hybrid system
warning light, check the diagnostic code.
6. EMPS malfunction
warning lightTurns on when there is a malfunction in the EMPS control system.
7. HV battery warning
lightTurns on when the HV battery is discharged to the lower limit.
8. Hybrid system
warning lightTurns on when a malfunction in MG1, 2, inverter, HV battery or HV ECU
is detected.

B04762
IN±14
± INTRODUCTIONFOR ALL OF VEHICLES
14 Author: Date:
2001 PRIUS (RM778U)
(b) Actions to be taken when HV battery is depleted
NOTICE:
Leaving a vehicle alone for 2 ± 3 months may cause electric
discharge from HV battery.
When this happens, replace the HV battery.
4. INSPECTION MODE
HINT:

The PRIUS automatically stops the engine while the ve-
hicle is stopped with the engine warmed up and battery
well charged if the A/C compressor operation is not re-
quired. Therefore, even if the vehicle stops for any reason
such as a check of ignition timing, the inspection mode
should be activated when continuous operation of the en-
gine is required.

The PRIUS has a skid control as traction control function.
When the wheel speed of the front wheels exceeds that
of the rear wheels, this function restrains the wheel speed
of the front wheels. It is necessary to activate the inspec-
tion mode and reset the skid control when turning only the
front wheels using a speedometer tester.
Activation inspection mode (Without using a hand±held tester)
(1) Perform the following (2) through (6) within 60 sec.
(2) Turn the ignition switch ON from OFF.
(3) With the shift lever in P position, fully depress the
accelerator pedal 2 times.
(4) With the shift lever in N position, fully depress the
accelerator pedal 2 times.
(5) With the shift lever in P position, fully depress the
accelerator pedal 2 times.
(6) Activate the inspecting mode and check that the hy-
brid system error warning light on the multi±center
display flashes.
(7) Turning the ignition switch to START starts the en-
gine's continuous operation.
NOTICE:

The idling speed in the inspection mode is approx.
1,000 rpm. The number of revolutions will increase up
to 1,500 rpm if the accelerator pedal is depressed to
a degree of less than 60%, and up to 2,250 rpm in a
case of 60% or more.

If a diagnosis code is recorded when entering the in-
spection mode, the master warning light and the error
warning light on the multi±center display is lit.

± INTRODUCTIONFOR ALL OF VEHICLES
IN±15
15 Author: Date:
2001 PRIUS (RM778U)

When the master warning light is lit during operation
in the inspection mode, deactivate the inspection
mode and inspect the diagnosed area.
HINT:
When continuous operation of the engine is required for such
as an exhaust leakage inspection, it is advisable as an easier
way to turn ON the FULL switch of the air conditioner.
5. SPECIAL NOTES FOR VEHICLE INSPECTION
(a) Vehicle conditions
(1) Before activating the service mode, turn the air con-
ditioner off, start the engine with the shift lever at P
position, and check that the engine stops within
several seconds after starting. (Engine warm up
check)
(2) Activate the service mode and inspect the vehicle.
The shift position for each test is as follows:
Test itemShift lever position
1. Vehicle straight traveling test (side
slip inspection)D
2. Braking force testN
3. Speedometer testD
4. Exhaust gas test (idling)P
5. Headlight testP
(3) Reset the service mode immediately after comple-
tion of inspection.
NOTICE:
Traveling on a road without resetting the service mode may
damage the transaxle.
(b) Special notes for speedometer test
NOTICE:
Rapid starting or quick acceleration/deceleration based on
the speedometer tester without load setting may damage
the transaxle.
(1) Depress the accelerator pedal slowly and gradually
accelerate at the time of measurement.
(2) After the measurement, use the brake to decelerate
gradually and stop.
(c) Special note for using the chassis dynamometer
Always set an appropriate load before starting the test.
NOTICE:
Rapid starting or quick acceleration/deceleration with in-
sufficient load may damage the transaxle.

V07268
VIBRATION METHOD: When vibration seems to be the major cause.
CONNECTORS
WIRE HARNESS
PARTS AND SENSOR1
Slightly shake the connector vertically and horizontally.
Slightly shake the wire harness vertically and horizontally.
The connector joint, fulcrum of the vibration, and body
through portion are the major areas to be checked thorough-
ly.
Apply slight vibration with a finger to the part of the sensor
considered to be the problem cause and check that the mal-
function occurs.Shake Slightly
Swing Slightly
Vibrate Slightly
HINT:
Applying strong vibration to relays may result in open relays.
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN±35
2001 PRIUS (RM778U)
3. SYMPTOM SIMULATION
The most difficult case in troubleshooting is when there are no problem symptoms occurring. In such cases,
a thorough customer problem analysis must be carried out, then simulate the same or similar conditions and
environment in which the problem occurred in the customer's vehicle. No matter how much experience a
technician has, or how skilled he may be, if he proceeds to troubleshoot without confirming the problem
symptoms he will tend to overlook something important in the repair operation and make a wrong guess
somewhere, which will only lead to a standstill. For example, for a problem which only occurs when the en-
gine is cold, or for a problem which occurs due to vibration caused by the road during driving, etc., the prob-
lem can never be determined so long as the symptoms are confirmed with the engine hot condition or the
vehicle at a standstill. Since vibration, heat or water penetration (moisture) is likely cause for problem which
is difficult to reproduce, the symptom simulation tests introduced here are effective measures in that the ex-
ternal causes are applied to the vehicle in a stopped condition.
Important Points in the Symptom Simulation Test:
In the symptom simulation test, the problem symptoms should of course be confirmed, but the problem area
or parts must also be found out. To do this, narrow down the possible problem circuits according to the symp-
toms before starting this test and connect a tester beforehand. After that, carry out the symptom simulation
test, judging whether the circuit being tested is defective or normal and also confirming the problem symp-
toms at the same time. Refer to the problem symptoms table for each system to narrow down the possible
causes of the symptom.

B02389
B02390
HEAT METHOD: When the problem seems to occur when the suspect area is heated. 2
NOTICE:3 WATER SPRINKLING METHOD:
(1)
(2)
4 OTHER: When a malfunction seems to occur when electrical load is excessive.When the malfunction seems to occur on a rainy day or in a
high±humidity condition. Heat the component that is the likely cause of the malfunction
with a hair dryer or similar object. Check to see if the malfunction
occurs.
Sprinkle water onto the vehicle and check to see if the malfunc-
tion occurs.
Turn on all electrical loads including the heater blower, head
lights, rear window defogger, etc. and check to see if the mal-
function occurs.ON HINT:
If a vehicle is subject to water leakage, the leaked water may
contaminate the ECU. When testing a vehicle with a water leak-
age problem, special caution must be taken.
Malfunc-
tion
Do not heat to more than 60 °C (140 °F). (Temperature
is limited not to damage the components.)
Do not apply heat directly to parts in the ECU. (1)
(2)
Never sprinkle water directly into the engine compart-
ment, but indirectly change the temperature and hu-
midity by applying water spray onto the radiator front
surface.
Never apply water directly onto the electronic compo-
nents. NOTICE: IN±36
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
2001 PRIUS (RM778U)

DI00H±16
FI0534
I12054
TOYOTA Hand±Held tester
DLC3
± DIAGNOSTICSENGINE
DI±3
2001 PRIUS (RM778U)
PRE±CHECK
1. DIAGNOSIS SYSTEM
(a) Description

When troubleshooting OBDII vehicles, the only dif-
ference from the usual troubleshooting procedure
is that you connect to the vehicle the OBDII scan
tool complying with SAE J1978 or TOYOTA hand±
held tester, and read off various data output from
the vehicle's ECM.

OBDII regulations require that the vehicle's on±
board computer lights up the Malfunction Indicator
Lamp (MIL) on the instrument panel when the com-
puter detects a malfunction in the emission control
system/components or in the powertrain control
components which affect vehicle emissions, or a
malfunction in the computer. In addition to the MIL
lighting up when a malfunction is detected, the ap-
plicable Diagnostic Trouble Code (DTC) prescribed
by SAE J2012 are recorded in the ECM memory
(See page DI±14).
If the malfunction does not reoccur in 3 consecutive trips, the
MIL goes off automatically but the DTCs remain recorded in the
ECM memory.

When DTC P3190, P3191 are detected and the re-
main of the fuel is little, the computer judges the
cause as a fuel shortage, and after the next trip,
when the supply of fuel is confirmed, it turns off MIL,
but the memory of DTC still remains.

To check the DTCs, connect the TOYOTA hand±
held tester or OBDII scan tool to Data Link Connec-
tor 3 (DLC3) on the vehicle. The TOYOTA hand±
held tester or OBDII scan tool also enables you to
erase the DTCs and check freezed frame data and
various forms of engine data. (For operating instruc-
tions, see the OBDII scan tool's instruction book.)

DTCs include SAE controlled codes and manufac-
turer controlled codes. SAE controlled codes must
be set as prescribed by the SAE, while manufactur-
er controlled codes can be set freely by the
manufacturer within the prescribed limits (See DTC
chart on page DI±14).

DI±4
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)

The diagnosis system operates in normal mode
during normal vehicle use. It also has a check mode
for technicians to simulate malfunction symptoms
and troubleshoot. Most DTCs use 2 trip detection
logic* to prevent erroneous detection, and ensure
thorough malfunction detection. By switching the
ECM to check mode when troubleshooting, the
technician can cause the MIL to light up for a mal-
function that is only detected once or momentarily
(TOYOTA hand±held tester only). (See step 2)

*2 trip detection logic:
When a malfunction is first detected, the malfunc-
tion is temporarily stored in the ECM memory (1st
trip).
If the same malfunction is first detected again during the second
drive test, this second detection causes the MIL to light up (2nd
trip). (However, the IG switch must be turned OFF between the
1st trip and the 2nd trip.)

Freeze frame data:
Freeze frame data records the engine condition
when a misfire (DTC P0300 ± P0304) or fuel trim
malfunction (DTC P0171, P0172) or other malfunc-
tion (first malfunction only), is detected.

Because freeze frame data records the engine
conditions (fuel system, calculated load, engine
coolant temperature, fuel trim,engine speed, ve-
hicle speed, etc.) when the malfunction is detected,
when troubleshooting it is useful for determining
whether the vehicle was running or stopped, the en-
gine warmed up or not, the air±fuel ratio lean or rich,
etc. at the time of the malfunction.
Priorities for troubleshooting:
If troubleshooting priorities for multiple DTCs are given in the
applicable DTC chart, these should be followed.
If no instructions are given troubleshoot DTCs according to the
following priorities.
(1) DTCs other than fuel trim malfunction (DTC P0171,
P0172), and misfire (DTC P0300 ± P0304).
(2) Fuel trim malfunction (DTC P0171, P0172).
(3) Misfire (DTC P0300 ± P0304).