Page 1057 of 2267
Wiring DiagramNCEC0277MODELS BEFORE VIN - P11U0548750
YEC844
IGNITION SWITCH
ON or START
Refer to EL-POWER.: Detectable line for DTC
: Non-detectable line for DTC
: Hyper CVT models
: M/T models FUSE
BLOCK
(J/B)
COMBINATION
METER
(SPEEDOMETER)
ECM
REFER TO THE FOLLOWING
FUSE BLOCK -
Junction Box (J/B) VEHICLE
SPEED
SENSOR BATTERY
DTC P0500 VEHICLE SPEED SENSOR (VSS)SR20DE
Wiring Diagram
EC-257
Page 1058 of 2267
MT MODELS WITH ABS AFTER VIN - P11U0548750
YEC091A
DTC P0500 VEHICLE SPEED SENSOR (VSS)SR20DE
Wiring Diagram (Cont'd)
EC-258
Page 1059 of 2267
EXCEPT MT MODELS WITH ABS AFTER VIN - P11U0548750
YEC092A
DTC P0500 VEHICLE SPEED SENSOR (VSS)SR20DE
Wiring Diagram (Cont'd)
EC-259
Page 1060 of 2267

Diagnostic ProcedureNCEC0278MODELS BEFORE VIN - P11U0548750
1 CHECK INPUT SIGNAL CIRCUIT
1. Turn ignition switch ªOFFº.
2. Disconnect ECM harness connector and combination meter harness connector.
3. Check harness continuity between ECM terminal 86 and meter terminal 9.
Refer to wiring diagram.
Continuity should exist.
4. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 3.
NG©GO TO 2.
2 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors F104, M50 (CVT: F115, M81)
IHarness for open or short between ECM and combination meter
©Repair open circuit or short to ground or short to power in harness or connectors.
Check Audio circuit and other linked circuit for short to ground or short to power power.
Refer to EL section.
3 CHECK SPEEDOMETER FUNCTION
Make sure that speedometer functions properly.
OK or NG
OK©GO TO 5.
NG©GO TO 4.
4 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors M50, F104 and M52, F103 (CVT: M81, F115 and M80, F114)
IHarness for open or short between combination meter and vehicle speed sensor
©Repair harness or connectors. Check vehicle speed sensor and its circuit. Refer to EL
section.
5 CHECK INTERMITTENT INCIDENT
Check combination meter internal circuit for short to ground or short to power. Refer to EL section.
Perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-SR-114.
©INSPECTION END
DTC P0500 VEHICLE SPEED SENSOR (VSS)SR20DE
Diagnostic Procedure
EC-260
Page 1061 of 2267

MT MODELS WITH ABS AFTER VIN - P11U0548750
1 CHECK INPUT SIGNAL CIRCUIT
1. Turn ignition switch ªOFFº.
2. Disconnect ECM harness connector and combination meter harness connector.
3. Check harness continuity between ECM terminal 86 and meter terminal 4.
Refer to wiring diagram.
Continuity should exist.
4. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 3.
NG©GO TO 2.
2 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors F104, M50 (CVT: F115, M81)
IHarness for open or short between ECM and combination meter
©Repair open circuit or short to ground or short to power in harness or connectors.
Check Audio circuit and other linked circuit for short to ground or short to power. Refer to
EL section.
3 CHECK SPEEDOMETER FUNCTION
Make sure that speedometer functions properly.
OK or NG
OK©GO TO 5.
NG©GO TO 4.
4 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors M50, F104
IHarness for open or short between combination meter and vehicle speed sensor
©Repair harness or connectors. Check vehicle speed sensor and its circuit. Refer to EL
section.
5 CHECK INTERMITTENT INCIDENT
Check combination meter internal circuit for short to ground or short to power. Refer to EL section.
Perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-SR-114.
©INSPECTION END
DTC P0500 VEHICLE SPEED SENSOR (VSS)SR20DE
Diagnostic Procedure (Cont'd)
EC-261
Page 1062 of 2267

EXCEPT MT MODELS WITH ABS AFTER VIN - P11U0548750
1 CHECK INPUT SIGNAL CIRCUIT
1. Turn ignition switch ªOFFº.
2. Disconnect ECM harness connector and combination meter harness connector.
3. Check harness continuity between ECM terminal 86 and meter terminal 4.
Refer to wiring diagram.
Continuity should exist.
4. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 3.
NG©GO TO 2.
2 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors F104, M50 (CVT: F115, M81)
IHarness for open or short between ECM and combination meter
©Repair open circuit or short to ground or short to power in harness or connectors.
Check Audio circuit and other linked circuit for short to ground or short to power power.
Refer to EL section.
3 CHECK SPEEDOMETER FUNCTION
Make sure that speedometer functions properly.
OK or NG
OK©GO TO 5.
NG©GO TO 4.
4 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors M80, F114 and M81, F115
IHarness for open or short between combination meter and vehicle speed sensor
©Repair harness or connectors. Check vehicle speed sensor and its circuit. Refer to EL
section.
5 CHECK INTERMITTENT INCIDENT
Check combination meter internal circuit for short to ground or short to power. Refer to EL section.
Perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-SR-114.
©INSPECTION END
DTC P0500 VEHICLE SPEED SENSOR (VSS)SR20DE
Diagnostic Procedure (Cont'd)
EC-262
Page 1063 of 2267

DescriptionNCEC0279SYSTEM DESCRIPTIONNCEC0279S01
Sensor Input Signal to ECMECM func-
tionActuator
Camshaft position sensor Engine speed
ECM IACV-AAC valve Engine coolant temperature sensor Engine coolant temperature
Ignition switch Start signal
Throttle position sensor Throttle position
PNP switch Park/Neutral position
Air conditioner switch Air conditioner operation
Power steering oil pressure switch Power steering load signal
Battery Battery voltage
Vehicle speed sensor or ABS actuator and
electric unit (control unit)Vehicle speed
Cooling fan Cooling fan operation
Electrical load Electrical load signal
This system automatically controls engine idle speed to a specified
level. Idle speed is controlled through fine adjustment of the
amount of air which by-passes the throttle valve via IACV-AAC
valve. The IACV-AAC valve changes the opening of the air by-pass
passage to control the amount of auxiliary air. This valve is actu-
ated by a step motor built into the valve, which moves the valve in
the axial direction in steps corresponding to the ECM output sig-
nals. One step of IACV-AAC valve movement causes the respec-
tive opening of the air by-pass passage. (i.e. when the step
advances, the opening is enlarged.) The opening of the valve is
varied to allow for optimum control of the engine idling speed. The
crankshaft position sensor (POS) detects the actual engine speed
and sends a signal to the ECM. The ECM then controls the step
position of the IACV-AAC valve so that engine speed coincides with
the target value memorized in ECM. The target engine speed is the
lowest speed at which the engine can operate steadily. The opti-
mum value stored in the ECM is determined by taking into consid-
eration various engine conditions, such as during warm up,
deceleration, and engine load (air conditioner, power steering, cool-
ing fan operation and electrical load).
COMPONENT DESCRIPTIONNCEC0279S02The IACV-AAC valve is operated by a step motor for centralized
control of auxiliary air supply. This motor has four winding phases
and is actuated by the output signals of ECM which turns ON and
OFF two windings each in sequence. Each time the IACV-AAC
valve opens or closes to change the auxiliary air quantity, the ECM
sends a pulse signal to the step motor. When no change in the
auxiliary air quantity is needed, the ECM does not issue the pulse
signal. A certain voltage signal is issued so that the valve remains
at that particular opening.
SEF937W
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð
AUXILIARY AIR CONTROL (AAC) VALVESR20DE
Description
EC-263
Page 1064 of 2267

CONSULT-II Reference Value in Data Monitor
Mode
NCEC0280
MONITOR ITEM CONDITION SPECIFICATION
IACV-AAC/VIEngine: After warming up
IAir conditioner switch: OFF
IShift lever: ªNº or ªPº
INo-loadIdle 5 - 20 steps
2,000 rpm Ð
ECM Terminals and Reference ValueNCEC0281Specification data are reference values and are measured between each terminal and 48 (ECM ground).
TER-
MINAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
6
7
15
16BR
Y/B
P
ORIACV-AAC valve[Engine is running]
IWarm-up condition
IIdle speed0 - 14V
On Board Diagnosis LogicNCEC0282
DTC No. Malfunction is detected when ... Check Items (Possible Cause)
P0505
0505IAn improper voltage signal is sent to ECM through the
valve.IHarness or connectors
(The IACV-AAC valve circuit is open.)
IIACV-AAC valve
DTC Confirmation ProcedureNCEC0283NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 9 seconds
before conducting the next test.
If the target idle speed is out of the specified value, perform
ªIdle Air Volume Learningº EC-SR-46, before conducting ªDTC
Confirmation Procedureº. For the target idle speed, refer to
the ªService Data and Specifications (SDS)º, EC-SR-330.
With CONSULT-II
1) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Start engine and warm it up to normal operating temperature.
4) Rev engine from idle to more than 2,000 rpm 20 times.
If 1st trip DTC is detected, go to ªDIAGNOSTIC
PROCEDUREº, EC-SR-266.
With GST
Follow the procedure ªWith CONSULT-IIº above.
NEF085A
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð
AUXILIARY AIR CONTROL (AAC) VALVESR20DE
CONSULT-II Reference Value in Data Monitor Mode
EC-264