Page 253 of 656

6-1-92 ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE)
DTC P0403 (DTC No.51) Exhaust Gas Recirculation Circuit Malfunction
WIRING DIAGRAM
DTC DETECTING CONDITION AND TROUBLE AREA
DTC CONFIRMATION PROCEDURE
1) Connect scan tool to DLC with ignition switch OFF.
2) Turn ON ignition switch and clear DTC, pending DTC and freeze frame data by using scan tool.
3) Start engine and run it for 10 sec.
4) Check DTC by using scan tool.
1. Main fuse 4. ECM (PCM)
2. Main relay
3. EGR valve
DTC DETECTING CONDITION TROUBLE AREA
High voltage is detected at EGR valve stepping motor
electrical circuit for specified time continuously.
(Circuit open or short).EGR valve (stepping motor) or its circuit ECM
(PCM)
NOTE:
Check to make sure that following condition is satisfied when using this “DTC CONFIRMATION PRO-
CEDURE”.
Intake air temp. : – 8°C (18°F) or higher
Engine coolant temp. : – 8 – 110°C (18 – 230°F)
Altitude (barometric pressure) : 2400 m, 8000 ft or less (560 mmHg (75 kPa) or more)
Page 255 of 656

6-1-94 ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE)
DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1)
SYSTEM DIAGRAM
CIRCUIT DESCRIPTION
Exhaust oxygen concentration at the pre-catalyst and the post-catalyst of WU-TWC is detected from HO2S-1
and HO2S-2 respectively and accordingly ECM (PCM) controls the closed loop which then controls the fuel
injection volume. (Refer to Section 6E2.) While the above control is going on and if WU-TWC is in good condi-
tion, the output voltage of HO2S-2 is maintained at specified level. As WU-TWC becomes deteriorated, even
when the above control is going on, the exhaust gas which has passed WU-TWC then passes HO2S-2 at the
exhaust oxygen concentration similar to that of the pre-catalyst without being oxygenated or converted. Thus,
waveforms of HO2S-1 and HO2S-2 output voltages become alike. ECM (PCM) judges deterioration of WU-TWC
by comparing waveforms of HO2S-1 and HO2S-2.
DTC DETECTING CONDITION AND TROUBLE AREA
1. HO2S-1 (Bank-1) 4. TWC
2. HO2S-2 (Bank-1) 5. ECM (PCM)
3. WU-TWC
DTC DETECTING CONDITION TROUBLE AREA
While running under conditions described for DTC CON-
FIRMATION PROCEDURE, output waveform of HO2S-1
becomes similar to that of HO2S-2.
(2 driving cycle detection logic)• Exhaust gas leakage
• Warm up three way catalytic converter
• Heated oxygen sensor – 2 or its circuit
•ECM (PCM)
Page 257 of 656

6-1-96 ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE)
DTC P0430 Catalyst System Efficiency Below Threshold (Bank 2)
SYSTEM DIAGRAM
CIRCUIT DESCRIPTION
Exhaust oxygen concentration at the pre-catalyst and the post-catalyst of WU-TWC is detected from HO2S-1
and HO2S-2 respectively and accordingly ECM (PCM) controls the closed loop which then controls the fuel
injection volume. (Refer to Section 6E2.) While the above control is going on and if WU-TWC is in good condi-
tion, the output voltage of HO2S-2 is maintained at specified level. As WU-TWC becomes deteriorated, even
when the above control is going on, the exhaust gas which has passed TWC then passes HO2S-2 at the
exhaust oxygen concentration similar to that of the pre-catalyst without being oxygenated or converted. Thus,
waveforms of HO2S-1 and HO2S-2 output voltages become alike. ECM (PCM) judges deterioration of WU-TWC
by comparing waveforms of HO2S-1 and HO2S-2.
DTC DETECTING CONDITION AND TROUBLE AREA
1. HO2S-1 (Bank-2) 4. TWC
2. HO2S-2 (Bank-2) 5. ECM (PCM)
3. WU-TWC
DTC DETECTING CONDITION TROUBLE AREA
While running under conditions described for DTC CON-
FIRMATION PROCEDURE, output waveform of HO2S-1
becomes similar to that of HO2S-2.
(2 driving cycle detection logic)• Exhaust gas leakage
• Warm up three way catalytic converter
• Heated oxygen sensor – 2 or its circuit
•ECM (PCM)
Page 259 of 656

6-1-98 ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE)
DTC P0443 Evap Control System Purge Control Valve Circuit Malfunction
SYSTEM/WIRING DIAGRAM
DTC DETECTING CONDITION AND TROUBLE AREA
DTC CONFIRMATION PROCEDURE
1. Main fuse 3. EVAP canister purge valve
2. Main relay 4. ECM (PCM)
DTC DETECTING CONDITION TROUBLE AREA
Monitor signal of EVAP canister purge valve is different
from command signal. (Circuit open or short)
(2 driving cycle detection logic)• EVAP canister purge valve and its circuit
•ECM (PCM)
WARNING:
When performing a road test, select a place where there is no traffic or possibility of a traffic acci-
dent and be very careful during testing to avoid occurrence of an accident.
Road test should be carried out with 2 persons, a driver and a tester, on a level road.
NOTE:
Check to make sure that following condition is satisfied when using the “DTC Confirmation Proce-
dure.”
Intake air temp. : – 8°C (18°F) or higher
Engine coolant temp. : – 8 – 110°C (18 – 230°F)
Altitude (barometric pressure) : 2400 m, 8000 ft or less (560 mmHg (75 kPa) or more)
Page 264 of 656

ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE) 6-1-103
DTC P0460 Fuel Level Sensor Circuit High Input
WIRING DIAGRAM/CIRCUIT DESCRIPTION
DTC DETECTING CONDITION AND TROUBLE AREA
DTC CONFIRMATION PROCEDURE
1) Connect scan tool to DLC with ignition switch OFF.
2) Turn ON ignition switch and clear DTC, pending DTC and freeze frame data by using scan tool and run
engine for 1 min.
3) Check pending DTC by using scan tool.
1. Fuel level sensor
2. Fuel meter in combination meter
3. ECM (PCM)
DTC DETECTING CONDITION TROUBLE AREA
Fuel level sensor output voltage higher than specified
value is detected for specified time.
(2 driving cycle detection logic)•Fuel level gauge or its circuit
•Fuel level sensor or its circuit
•ECM (PCM)
NOTE:
Check to make sure that following condition is satisfied when using this “DTC CONFIRMATION PRO-
CEDURE”.
Intake air temp. : – 8°C (18°F) or higher
Engine coolant temp. : – 8 – 110°C (18 – 230°F)
Altitude (barometric pressure) : 2400 m, 8000 ft or less (560 mmHg (75 kPa) or more)
Page 266 of 656
ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE) 6-1-105
DTC P0500 (DTC No.24) Vehicle Speed Sensor Malfunction
WIRING DIAGRAM
DTC DETECTING CONDITION AND TROUBLE AREA
1. Speedometer
2. Vehicle speed sensor
3. Cruise control module (if equipped)
4. ECM (PCM)
DTC DETECTING CONDITION TROUBLE AREA
Vehicle speed signal not inputted although fuel is kept
cut for longer than 5 seconds
(2 driving cycle detection logic)•Vehicle speed sensor circuit open or short
•Vehicle speed sensor
•Vehicle speed sensor drive gear or driven gear
•Speedometer malfunction
•Cruise control module malfunction (if equipped)
•ECM (PCM)
Page 269 of 656
6-1-108 ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE)
DTC P0505 Idle Air Control System Malfunction
SYSTEM/WIRING DIAGRAM
DTC DETECTING CONDITION AND TROUBLE AREA
1. Throttle body 3. ECM (PCM) 5. FIA valve 7. Main relay
2. Idle air control valve 4. Sensed information 6. Main fuse
DTC DETECTING CONDITION TROUBLE AREA
•Engine idle speed is 100 r/min. or more lower than target idle
speed for longer than 20 sec. continuously.
or
•Engine idle speed is 200 r/min or more higher than target
idle speed for longer than 20 sec. continuously.
(2 driving cycle detection logic)•IAC valve or its circuit
•Abnormal air drawn in air intake system
•FIA (fast idle air) valve
Page 272 of 656

ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE) 6-1-111
DTC P1408 Manifold Absolute Pressure Sensor Circuit Malfunction
WIRING DIAGRAM
DTC DETECTING CONDITION AND TROUBLE AREA
DTC CONFIRMATION PROCEDURE
1. MAP sensor
2. ECM (PCM)
DTC DETECTING CONDITION TROUBLE AREA
•While engine is running after being warmed up and
with throttle opening smaller than specification,
higher than 4.6 V manifold absolute pressure sen-
sor output voltage is detected for specified time or
with throttle opening larger than specification, lower
than 0.2 V manifold absolute pressure output volt-
age is detected for specified time.
(2 driving cycle detection logic)•Manifold absolute pressure sensor
•Manifold absolute pressure sensor vacuum pas-
sage
•ECM (PCM)
WARNING:
When performing a road test, select a place where there is no traffic or possibility of a traffic acci-
dent and be very careful during testing to avoid occurrence of an accident.
Road test should be carried out with 2 persons, a driver and a tester, on a level road.
NOTE:
Check to make sure that following condition is satisfied when using this “DTC CONFIRMATION PRO-
CEDURE”.
Intake air temp. : – 8°C (18°F) or higher
Engine coolant temp. : – 8 – 110°C (18 – 230°F)
Altitude (barometric pressure) : 2400 m, 8000 ft or less (560 mmHg (75 kPa) or more)