Ecs Cec System Toyota Camry V10

DESCRIPTION

The Toyota EFI Electronic Control System (ECS) is a computerized fuel control system. The ECS controls engine operation and lowers exhaust emissions while maintaining good fuel economy and driveability. The Electronic Control Unit (ECU) is the "brain" of the ECS. The ECU controls many engine related systems to constantly adjust engine operation.

The ECS is primarily an emission control system, designed to maintain an ideal air/fuel ratio of 14.7:1 under all operating conditions. When an ideal air/fuel ratio is maintained, the catalytic converter can control carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) emissions.

Camry Electronic Control System Schematic. Scheme 11

OPERATION

The ECS consists of the following subsystems: Electronic Fuel Injection (EFI) system, Data Sensors, Electronic Control Unit (ECU), Electronic Controlled Transmission (ECT), Fuel Cut System, Charge Warning System, Diagnostic System and catalytic converter.

ELECTRONIC FUEL INJECTION (EFI)

All models are equipped with Bosch AFC fuel injection system. An electric fuel pump provides fuel to the fuel pressure regulator. From the regulator, fuel flows under pressure to the fuel injectors. The pressure regulator maintains uniform pressure differential at all times.

The constant pressure differential allows the ECU to control length of injection rather than amount of injection. The ECU monitors engine operating conditions and calculates injection duration for efficient engine operation.

The ECU activates all the injectors at the same time. When the injectors are activated, they provide 1/2 the amount of fuel required for ideal combustion with each engine revolution. See appropriate FOSCH AFC FUEL INJECTION article.

DATA SENSORS

Each sensor furnishes electrical impulses to ECU. The ECU computes fuel delivery and spark timing necessary to maintain desired air/fuel ratio and engine speed. Data sensors are interrelated to each other. Operation of each sensor is as follows

Air Flow Sensor

This sensor is mounted within the air flow meter. The sensor measures air flow rate through the air flow meter and sends a proportionate electrical signal to the ECU. The ECU uses air flow sensor information for controlling fuel injection duration.

Air Temperature Sensor

This sensor is mounted within the air flow meter. The sensor measures temperature of incoming air and sends an electrical signal to ECU. The ECU uses air temperature information for controlling fuel injection duration.

Throttle Position Sensor (TPS)

The throttle position sensor (TPS) is mounted on throttle body and is directly connected to throttle linkage. The sensor, a rotary potentiometer, signals ECU of changes in throttle valve position. The information provided by this sensor is used for controlling fuel injection duration.

Coolant Temperature Sensor

The coolant temperature sensor is installed in intake manifold on Camry models. This sensor is a thermosensor which converts temperature of engine coolant to electrical signal for use by ECU. The ECU uses coolant temperature information for controlling fuel injection duration.

Oxygen Sensor

The oxygen sensor is installed in exhaust manifold. Output voltage of oxygen sensor varies with oxygen content of exhaust gases. The ECU uses exhaust gas oxygen content information for determining fuel injection duration.

Vehicle Speed Sensor (VSS)

This sensor is mounted in the instrument panel and is a component of the speedometer on Camry models only. Vehicle speed information is used by the ECU for electronic control of automatic transmission.

Engine Speed

Engine speed signal information is received from the ignition coil. These signals are used by the ECU for fuel injection duration control.

A/C Switch

On Camry models, a signal is sent to ECU when the air conditioner is activated. The ECU requires this input to increase idle speed during A/C operation.

ELECTRONIC CONTROL UNIT (ECU)

The ECU is mounted in center console under instrument panel. The ECU controls all functions of the ECS. The ECU consists of a printed circuit board enclosed within a metal box. The ECU receives signals from the data sensors and switches. These signals are processed by the ECU for controlling various engine functions.

Camry ECS Component Locations. Scheme 12

ELECTRONIC CONTROLLED TRANSMISSION (ECT)

Automatic transmission Camry models are equipped with an electronic control unit to control transmission operation. The ECU of the ECS provides signals on engine operation to the ECU of the ECT system. This information is used by the ECT computer to prevent shift up to 3rd gear or overdrive during cold engine operation.

Note. The ECU of the ECS is not interchangeable with the ECU of the ECT system.

FUEL CUT SYSTEM

All models are equipped with an electronically controlled fuel cut system. During sudden deceleration, the ECU adjusts fuel injection duration to prevent overloading the engine with fuel. The system also maintains smooth engine operation to prevent backfiring.

CHARGE WARNING SYSTEM

The ECU monitors alternator output. If a problem is detected in charging system or alternator output is not to specifications, the "CHARGE" warning light will be lit.

DIAGNOSTIC SYSTEM

The ECU of the ECS is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, the ECU lights the "CHECK ENGINE" lamp located on instrument panel. At the same time, a corresponding trouble code is stored in ECU memory. Interpretation of the trouble codes can be performed by observing number of flashes of "CHECK ENGINE" lamp.

All codes are stored in memory from the time of detection until the codes are cleared from the memory. The "CHECK ENGINE" lamp will go out as soon as the malfunction is cleared; but the code will remain in memory.

As a bulb and system check, the "CHECK ENGINE" lamp will glow when ignition switch is turned on and engine is not running. When engine is started, the lamp should go out after a short period of time. If not, a malfunction has been detected in the ECS.

CATALYTIC CONVERTER

All models are equipped with 3-way catalytic converters. This type of converter changes CO, HC, and NOx exhaust emissions into carbon dioxide, water vapor and nitrogen gas. All converters are monolithic type.

DIAGNOSIS

Note. If vehicle is equipped with a mobile radio system (even with about 10 watts output), it may at times, have an affect upon ECU operation, especially if the antenna and feeder are installed nearby. Keep antenna as far as possible from the ECU wires. DO NOT equip vehicle with a powerful mobile radio system.

Diagnose ECS in the following order

1. Ensure that all engine systems NOT related to ECS are fully operational. Do not proceed with testing until you are sure that all other problems have been fixed. Always check fuses, fusible links and wire connectors before condemning the ECU.
2. Enter diagnostic mode and record trouble codes. Exit diagnostic mode. If no trouble codes were displayed, go to Diagnostic Circuit Check chart. Follow instructions given there.
3. If no trouble codes were displayed after performing Diagnostic Circuit Check, perform voltage and resistance checks. If trouble codes are displayed, perform tests to confirm cause of malfunction which set the corresponding trouble code.
4. After any repairs are made, clear trouble codes and perform Diagnostic Circuit Check. Normal system operation code should be displayed if repair solved cause of malfunction.

Note. The following paragraphs explain the procedures involved in performing the steps outlined above.

RECALLING TROUBLE CODES

The ECU stores component failure information for ECS under a related trouble code which can be recalled for diagnosis and repair. When recalled, these codes will be displayed by flashes of the "CHECK ENGINE" lamp.

Codes are displayed starting with lowest numbered code. Only codes in which a related malfunction has occurred will be displayed.

Entering Diagnostic Mode

1. Prior to entering diagnostic mode, the following conditions must be met: Engine must be at normal operating temperature, battery voltage above 11 volts, transmission in Neutral, throttle valve fully closed and A/C off.
2. Turn ignition on, but DO NOT start engine. Remove rubber cap from "CHECK ENGINE" connector. (Scheme 14) Using a jumper wire, jumper both terminals of the connector together.

Example of Trouble Code Output. Scheme 13

Jumping "CHECK ENGINE" Connector. Scheme 14

Diagnostic Code Output

1. After entering diagnostic mode, the "CHECK ENGINE" lamp should flash a code. If no trouble codes are stored in memory, the lamp should flash once every 3 seconds. This is the "system normal" code. (Scheme 13)
2. If trouble codes are stored in ECU memory, the "CHECK ENGINE" lamp will flash once every second. If code "6" is stored in memory, the lamp will flash 6 times in 6 seconds.
3. Trouble codes will be displayed from lowest to highest numbered code. Output of the diagnostic codes will continue as long as the diagnostic mode is activated. A 3-second delay follows display of each code.

EFI TROUBLE CODE IDENTIFICATION

Clearing Trouble Codes

After any repairs are performed, clear ECU memory of all stored trouble codes. To clear memory, turn ignition off and remove appropriate fuse from fuse panel for 30 seconds. Cancellation can also be done by removing the battery negative terminal, but in this case other memory systems (radio, clock, etc.) will also be canceled out. (Scheme 15)

Clearing Trouble Codes from ECU Memory. Scheme 15

Exiting Diagnostic Mode

To exit diagnostic mode, remove jumper wire from "CHECK ENGINE" connector. Turn ignition off. Replace rubber caps over connectors. After cancellation, perform a road test, if necessary, to confirm that a "normal" code is now read on "CHECK ENGINE" warning light.

ECS Voltage Tests

The ECS can be checked using a volt/ohmmeter. Before making voltage tests, make sure battery voltage is at least 11 volts. Perform voltage tests with harness connectors connected to ECU and ignition switch on. Connect probes to each wire cavity of ECU connectors. If voltage values are not as specified, perform resistance tests.

ECS Resistance Tests

The ECS can be checked using an volt/ohmmeter. Before making resistance tests, turn ignition off and disconnect wiring connectors at ECU. Insert volt/ohmmeter probes into wiring connectors from wire side. Measure resistance at connector terminals, NOT ECU terminals.

TROUBLE CODES & PROBABLE CAUSE FOR CODES

Electronic Control Unit Connector Identification. Scheme 16

TCCS VOLTAGE AND RESISTANCE TESTING

TCCS VOLTAGE SPECIFICATION CHART

TCCS RESISTANCE SPECIFICATION CHART

Diagnostic Circuit Check. Scheme 17

Terminals No. 10 & No. 20 - E1. Scheme 18

Terminals THA - E2 & Terminals Vc - E2, Vs - E2. Scheme 19

Terminals THW - E2. Scheme 20

Terminals THW - E2 (1 of 2). Scheme 21

Terminals THW - E2 (2 of 2). Scheme 22

Terminals IG - E1. Scheme 23

Terminals STA - E1. Scheme 24

Terminals TL - E1. Scheme 25

Terminals IDL - E1, PSW - E1. Scheme 26

Terminals + B - E1. Scheme 27

Terminals BAT - E1. Scheme 28

Terminals W - E1. Scheme 29

Terminals A/C - E1. Scheme 30

Charge Warning System Check. Scheme 31

AIR FLOW METER

Turn ignition off. Disconnect wiring connector from air flow meter. Using an ohmmeter, measure resistance between each terminal. (Scheme 32) If resistance values do not meet specifications shown in chart, replace air flow meter.

Measuring Air Flow Meter Resistance. Scheme 32

AIR FLOW METER RESISTANCE SPECIFICATIONS

Turn Ignition Off and disconnect electrical connector at TPS. Insert a thickness gauge between throttle stop screw and throttle lever. Using an ohmmeter, check resistance values. (Scheme 33) If values are not as specified in chart, adjust or replace TPS.

Checking Throttle Position Sensor. Scheme 33

TPS RESISTANCE SPECIFICATIONS

FUEL CUT DECELERATION SYSTEM

1. Connect tachometer to engine. Start and warm engine to normal operating temperature.
2. Disconnect wiring connector from throttle position sensor. Using a jumper wire, short-circuit terminals TL and IDL on wiring connector.
3. Slowly raise engine speed and watch tachometer. Tachometer should fluctuate between 1900-1600 RPM (Auto. Trans.) or 2000-1600 RPM (Man. Trans.).

1. Loosen 2 TPS retaining screws. Insert a .028" (.70 mm) thickness gauge between throttle stop screw and throttle. With ignition off and electrical connector disconnected, connect ohmmeter between terminals IDL and TL.
2. Gradually turn TPS counterclockwise until ohmmeter needle deflects. Secure TPS retaining screws. Perform resistance tests for terminals IDL - TL.

Camry ECS Wiring Diagram. Scheme 34