4afe
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ENGINEÐ4A±FE ENGINE |
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8. Diagnosis
The diagnostic system in the 4A±FE engine for the new Celica monitors fourteen conditions in the chart below. The purpose of this system is the same as the 4A±FE engine for '89 model AE95 series, but diagnostic items have been changed to match the 4A±FE engine for the new Celica.
Diagnostic Items
Code |
Item |
Diagnosis |
Trouble Area |
ªCHECK |
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ENGINEº |
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No. |
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Lamp |
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Distributor circuit |
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12 |
RPM Signal |
No ªNeº signal to ECU within 2 |
Distributor |
ON |
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seconds after the engine is cranked. |
Starter signal circuit |
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ECU |
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No ªNeº signal to ECU when the |
Distributor circuit |
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13 |
RPM Signal |
Distributor |
ON |
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engine speed is above 1000 rpm. |
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ECU |
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No ªIGfº signal to ECU 4 times in |
Igniter circuit |
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14 |
Ignition Signal |
Igniter |
ON |
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succession. |
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ECU |
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During air±fuel ratio feedback |
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correction, voltage output from the |
Oxygen sensor circuit |
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21 |
Oxygen Sensor |
oxygen sensor does not exceed a set |
ON |
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Signal |
value on the lean side and the rich |
Oxygen sensor |
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side continuously for a certain |
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period. |
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Water Temp. |
Open or short circuit in water temp. |
Water temp. sensor circuit |
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22 |
Water temp. sensor |
ON |
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Sensor Signal |
sensor signal (THW). |
ECU |
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Intake Air |
Open or short circuit in intake air |
Intake air temp. sensor circuit |
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24 |
Temp. Sensor |
Intake air temp. sensor |
ON* |
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temp. sensor signal (THA). |
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Signal |
ECU |
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Injector circuit |
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Injector |
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Air±fuel Ratio |
1)* When air±fuel ratio feedback |
Fuel line pressure |
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25 |
correction value or adaptive control |
Oxygen sensor circuit |
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ON* |
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Lean |
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Malfunction |
value continues at the upper (lean) |
Oxygen sensor |
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or lower (rich) limit for a certain |
Manifold pressure sensor |
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period of time or adaptive control |
Water temp. sensor |
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value is not renewed for a certain |
ECU |
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period of time. |
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Injector circuit |
ON |
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Injector |
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2)* When marked variation is |
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detected in engine revolutions for |
Fuel line pressure |
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Air±fuel Ratio |
each cylinder during idle switch on |
Oxygen sensor circuit |
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and feedback condition. |
Oxygen sensor |
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26 |
Rich |
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ON* |
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Cold start injector circuit |
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Malfunction |
3)Open or short circuit in oxygen |
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Cold start injector |
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sensor signal (Ox). |
Manifold pressure sensor |
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Water temp. sensor |
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ECU |
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*: Applicable only to California specification vehicles.
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ENGINEÐ4A±FE ENGINE |
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Code |
Item |
Diagnosis |
Trouble Area |
ªCHECK |
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ENGINEº |
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No. |
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Lamp |
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Manifold pressure sensor |
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31 |
Manifold |
Open or short circuit in manifold |
circuit |
ON |
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Pressure Sensor |
pressure sensor signal (PIM). |
Manifold pressure sensor |
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Signal |
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ECU |
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Throttle |
The ªIDLº and ªPSWº signals are |
Throttle position sensor circuit |
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41 |
Position Sensor |
output simultaneously for several |
Throttle position sensor |
ON* |
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Signal |
seconds. |
ECU |
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Vehicle Speed |
Open or short circuit in vehicle |
Vehicle speed sensor circuit |
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42 |
Vehicle speed sensor |
OFF |
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Sensor Signal |
speed sensor signal. |
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ECU |
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No ªSTAº signal to ECU until |
Starter signal circuit |
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Ignition switch, main relay |
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43 |
Starter Signal |
engine speed reaches 800 rpm with |
OFF |
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circuit |
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vehicle not moving. |
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ECU |
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EGR gas temp. below a |
EGR system components |
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predetermined level during EGR |
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EGR System |
EGR gas temp. sensor circuit |
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71* |
operation. |
ON |
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Malfunction |
EGR gas temp. sensor |
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Open circuit in EGR gas temp. |
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ECU |
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sensor signal (THG). |
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A/C amplifier |
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A/C switch circuit |
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Switch |
No ªIDLº signal or No ªNSWº |
Neutral start switch circuit |
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Neutral start switch |
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signal or ªA/Cº signal to ECU, with |
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51 |
Condition |
OFF |
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the check terminals T and E1 |
Accelerator pedal and cable |
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Signal |
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connected. |
Throttle position sensor circuit |
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Throttle position sensor |
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ECU |
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*: Applicable only to California specification vehicles. |
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NOTE: If two or more malfunctions are present at the same time, the lowest±numbered diagnostic code will be displayed first.
All detected diagnostic codes, except 51, will be retained in memory by the ECU from the time of detection until cancelled out.
Once the malfunction is corrected, the ªCHECK ENGINEº warning lamp will go out but the diagnostic code(s) will remain stored in the ECU memory (except for code 51).
After the malfunction is corrected, the diagnostic code is cleared by removing the EFI fuse for more than 10 seconds with the ignition switch off.
104 |
ENGINEÐ4A±FE ENGINE |
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EMISSION CONTROL SYSTEM
1.System Purpose
System |
Abbreviation |
Purpose |
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Positive crankcase ventilation |
PCV |
Reduces blow±by gas (HC) |
Evaporative emission control |
EVAP |
Reduces evaporative HC |
Exhaust gas recirculation |
EGR |
Reduces NOx |
Three±way catalyst |
TWC |
Reduces HC, CO and NOx |
Electronic fuel injection |
EFI |
Regulates all engine conditions for reduction |
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of exhaust emission |
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2. Component Layout and Schematic Drawing
*: Applicable only to California specification vehicles.