DESCRIPTION
The Toyota Computer Control System (TCCS) is a computerized emission, ignition and fuel control system. The TCCS controls Electronic Fuel Injection (EFI), engine operation and lowers exhaust emissions while maintaining good fuel economy and driveability.
The Electronic Control Unit (ECU) controls the TCCS. The ECU contains data used for maintaining ignition timing under all operating conditions. Input from various sensors allows the ECU to deliver spark at precise timing. The ECU controls engine related systems to adjust engine operation.
The TCCS is primarily an emission control system, designed to maintain proper air/fuel ratio at all operating conditions.
OPERATION
The TCCS consists of the following subsystems: Electronic Fuel Injection (EFI) system, data sensors, Electronic Control Unit (ECU), Electronic Spark Advance (ESA) system, Idle Speed Control (ISC) system, EGR Control, Electronic Controlled Transmission (ECT), diagnostic system and catalytic converter.
ELECTRONIC FUEL INJECTION (EFI)
All models are equipped with a Bosch AFC fuel injection system. An electric fuel pump provides fuel to the fuel pressure regulator. Pressure regulator maintains constant fuel pressure to the injectors.
The ECU controls the injection duration in accordance with engine conditions to provide efficient engine operation. For more information, see BOSCH AFC FUEL INJECTION article in the FUEL SYSTEMS section.
DATA SENSORS
Note. The following data sensors are not necessarily used on every model. Note engine application. See TOYOTA ENGINE CODE IDENTIFICATION chart and appropriate computer control system schematic. (Scheme 56)through (Scheme 58).
A/C Switch
Switch sends a signal to the ECU during A/C operation. ECU uses this signal for controlling idle speed during A/C operation.
Airflow Sensor
Airflow sensor, mounted within the airflow meter, measures airflow rate through the airflow meter. Signal is sent to ECU for controlling fuel injection duration and spark advance system.
Air Temperature Sensor
Sensor is mounted in the airflow meter. Sensor measures incoming air temperature. Signal is sent to ECU for controlling fuel injection duration.
Cold Start Injector Time Switch
Switch determines coolant temperature and sends signal to ECU on some models for cold start injector control.
Coolant Temperature Sensor
Coolant temperature sensor sends signal to ECU in relation to coolant temperature. ECU uses sensor signal for controlling fuel injection duration, spark advance system, idle speed control system and EGR system.
Coolant Temperature Switch
Switch monitors coolant temperature and sends signal to ECU.
EGR Gas Temperature Sensor
Sensor determines EGR gas temperature and sends signal to ECU.
Engine Speed
Engine speed signal information is received from the ignition coil. The ECU uses these signals for fuel injection duration control and spark advance system operation.
Knock Sensor
Sensor monitors ignition knock conditions and sends signal to ECU.
Neutral/Start Switch
Switch is installed on A/T models to inform ECU of gear selection. Information is used by the ECU to allow starter operation and control engine idle.
Oxygen (O2) Sensor
Oxygen sensor is installed in the exhaust system and monitors oxygen content of exhaust gases. Signal is sent to the ECU and is used for determining fuel injection duration.
Sub-Oxygen Sensor (Calif. Only)
Sensor is used in conjunction with O2 sensor. Sensor monitors oxygen content of exhaust gases and sends signal to the ECU.
Throttle Position Sensor (TPS)
Throttle Position Sensor (TPS) is mounted on throttle body. Sensor determines changes in throttle valve positions and send signals to the ECU. Signals are used for controlling fuel injection duration and idle speed control system.
Turbo Pressure Sensor
Sensor monitors turbo pressure and sends signal to ECU.
Vehicle Speed Sensor (VSS)
Sensor is used to monitor vehicle speed. Vehicle speed information is used by the ECU for cruise control and electronic control of automatic transmission.
4WD Switch
Switch indicates 4WD operation and sends signal to ECU.
| Application | Code |
|---|---|
| 4-Cylinder Engine | 3S-FE |
| V6 Engine | 2VZ-FE |
TOYOTA ENGINE CODE IDENTIFICATION
ELECTRONIC CONTROL UNIT (ECU)
The ECU controls all functions of the TCCS. The ECU receives signals from the data sensors and switches. Signals are processed by the ECU for controlling the Electronic Fuel Injection (EFI), Electronic Spark Advance (ESA), Idle Speed Control (ISC), Electronic Controlled Transmission (ECT) and EGR systems.
The ECU contains a fail-safe function used in case of a data sensor or switch failure. This function provides a back-up system to provide minimal driveability. The "CHECK ENGINE" light will also be activated during this function.
DIAGNOSTIC SYSTEM
The ECU is equipped with a self-diagnostic system which detects system failures or abnormalities. When malfunction occurs, the "CHECK ENGINE" light on instrument panel is activated. On models with Super Monitor Display, trouble code may be obtained from the screen on the instrument panel.
By analyzing various signals, the ECU detects system malfunctions related to various operating parameter sensors. The ECU stores trouble codes associated with the detected failure until the diagnostic system is cleared. The "CHECK ENGINE" light will go out when trouble codes are cleared.
Scheme 54
Scheme 55
Scheme 56
Scheme 57
Scheme 58
DIAGNOSIS
- Ensure all engine systems NOT related to TCCS are fully operational. DO NOT proceed with testing until all other problems have been repaired. Ensure fuses, fusible links and wire connectors are in good condition before diagnosing ECU.
- Enter diagnostic mode and record trouble codes. Exit diagnostic mode. If no trouble codes were displayed, proceed to appropriate DIAGNOSTIC CIRCUIT CHECK charts. Follow instructions given there.
- If no trouble codes were displayed after performing diagnostic circuit check, perform voltage and resistance checks. See appropriate «ECU PIN VOLTAGE TEST»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) chart in this article.
- If trouble codes are displayed, perform tests to confirm cause of malfunction which set the corresponding trouble code.
- 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.
CHECK ENGINE LIGHT
Turn ignition on. The "CHECK ENGINE" light will activate with ignition on and engine not running. Start engine and note that light is not activated. If light remains activated, a system malfunction or abnormality exists.
Scheme 59
- Ensure battery voltage is greater than 11 volts and throttle valve is fully closed. Place transmission or transaxle in Neutral and turn off all accessory switches.
- To enter diagnostic mode, turn ignition on. DO NOT start engine. Install jumper wire between terminals of engine check connector. (Scheme 59)
- Count number of flashes from "CHECK ENGINE" light. If system is operating properly (with no codes), "CHECK ENGINE" light will blink continuously and evenly.
- On all models, a code will be identified by a.5 second flash on and off for the first number. A 1.5 second pause will occur followed by the second number. (Scheme 60)
- If more than one code is stored, a 2.5 second pause will occur prior to the flashing of the second code. Once all codes have been displayed, a 4.5 second pause will occur and code(s) will repeat.
- On all models, trouble codes are given from smallest value in order to largest value. After code(s) are retrieved, remove jumper wire to exit diagnostic mode.
- Compare trouble code to that listed to locate probable cause. See appropriate «TROUBLE CODE IDENTIFICATION»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) and «TROUBLE CODES & PROBABLE CAUSE»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) tables.
| CAUTION | Ensure trouble codes are cleared after performing repair. Road test and recheck that trouble code does not exist. |
Clearing Trouble Codes
- After repairs are performed, clear ECU memory of all stored trouble codes. To clear memory, turn ignition off and remove fuse from fuse block for 30 seconds or more. See «CLEARING DIAGNOSTIC CODES»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) table for appropriate fuse removal.
- Fuse may require to be removed longer depending on the ambient temperature. Replace fuse and exit diagnostic mode. Trouble codes can also be cleared by disconnecting vehicle battery. However, other memory functions (clock, etc.), will need to be reset.
| Application | Fuse (Amperage) |
|---|---|
| Camry | EFI (15) |
CLEARING DIAGNOSTIC CODES
Scheme 60
SYSTEM TESTING
- If trouble codes exist and diagnostic circuit check has been performed, compare code with appropriate code chart for circuits and components associated with trouble code(s). Trouble code flow charts are arranged in alphabetical order by each model. A test No. has been assigned each chart. The test No. and trouble code are in numerical order for each model. All ECU pin identifications are at end of «TROUBLE CODES & PROBABLE CAUSE»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) charts.
- If no code is present, circuit checking is necessary. Each model has an ECU PIN VOLTAGE TEST after «DIAGNOSTIC CIRCUIT CHECK»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) flow chart. DIAGNOSTIC CIRCUIT CHECK flow chart is the first flow chart on each model. Using appropriate ECU PIN VOLTAGE TEST, check appropriate circuits using the test No. in the right column of the appropriate table. See «CODE CHARTS»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) .
- Component testing will also be necessary. All component testing available pertaining to CEC, follow the CEC flow charts. For components not covered, see appropriate article in FUEL or DISTRIBUTORS & IGNITION SYSTEMS.
| Code No. | Circuit Affected |
|---|---|
| No Code | System Normal |
| 11 | ECU (B+) |
| 12 & 13 | RPM Signal |
| 14 | Ignition Signal |
| 21 | Oxygen Sensor Signal |
| 22 | Coolant Temp. Sensor Signal |
| 24 | Intake Air Temp. Sensor Signal |
| 25 (1) | Lean Air/Fuel Mixture |
| 26 (1) | Rich Air/Fuel Mixture |
| 27 (2) | Sub-Oxygen Sensor Signal |
| 31 | Airflow Meter Signal |
| 32 | Airflow Meter Signal |
| 41 | Throttle Position Sensor Signal |
| 42 | Vehicle Speed Sensor Signal |
| 43 | Starter Signal |
| 51 | Switch Signal |
| 71 (3) | EGR System Malfunction |
| (1) Only applicable to 2VZ-FE & 4WD models. (2) Only applicable to California applications of 2VZ-FE models. (3) Only applicable to California applications of 2VZ-FE and 4WD models. | |
| (1) | Only applicable to 2VZ-FE & 4WD models. |
| (2) | Only applicable to California applications of 2VZ-FE models. |
| (3) | Only applicable to California applications of 2VZ-FE and 4WD models. |
TROUBLE CODE IDENTIFICATION
| Code No. | Probable Cause |
|---|---|
| 11 | Main Relay and/or Circuit, Ignition Switch and/or Circuit, ECU |
| 12 | Distributor and/or Circuit, Starter Signal, ECU |
| 13 | Distributor and/or Circuit, ECU |
| 14 | Ignition Coil, Ignitor and/or Circuit, ECU |
| 21 | O2 Sensor and/or O2 Heater Signal and/or Circuit, ECU |
| 22 | Coolant Temp. Sensor and/or Circuit, ECU |
| 24 | Intake Air Temp. Sensor or Circuit, ECU |
| 25 (1) | Injector and/or Circuit, O2 Sensor and/or, Circuit, Fuel Line Pressure, Airflow Meter, Coolant Temp. Sensor, Ignition System, ECU |
| 26 (1) | Injector and/or Circuit, Fuel Line Pressure, Cold Start Injector, Airflow Meter, Coolant Temp. Sensor, ECU |
| 27 (2) | Sub-O2 Sensor/Heater and/or Circuit, ECU |
| 31 | Airflow Meter and/or Circuit, ECU and/or Circuit, ECU Airflow Meter, ECU, Intercooler |
| 41 | Throttle Position Sensor and/or Circuit, ECU |
| 42 | Speed Sensor and/or Circuit, ECU |
| 43 | Ignition Switch and/or Circuit, ECU |
| 51 | Throttle Position Sensor and/or Circuit Switch Circuit, A/C Amplifier, ECU Neutral/Start Switch and/or Circuit, Accelerator Pedal and/or Cable and/or Circuit, Intercooler Water Pump and/or Circuit, Intercooler ECU, ECU |
| 71 (3) | EGR System, EGR Gas Temp. Sensor and/or Circuit, BVSV for EGR and/or Circuit, ECU |
| (1) 4WD & V6 California models only. (2) V6 California models only. (3) 4WD & V6 California models only. | |
| (1) | 4WD & V6 California models only. |
| (2) | V6 California models only. |
| (3) | 4WD & V6 California models only. |
TROUBLE CODES & PROBABLE CAUSE
Connector Pin Identification (2WD 3S-FE ECU). Scheme 61
Connector Pin Identification (All TRAC 4WD, 3S-FE ECU). Scheme 62
Connector Pin Identification (V6, 2V2-FE ECU). Scheme 63
Diagnostic Circuit Check, Schematic (4-Cyl.). Scheme 64
Diagnostic Circuit Check, Flow Chart (4-Cyl.). Scheme 65
Diagnostic Circuit Check, Schematic (V6). Scheme 66
Diagnostic Circuit Check, Flow Chart (V6). Scheme 67
ECU Pin Voltage Test (4-Cyl.). Scheme 68
ECU Pin Voltage Test (V6). Scheme 69
No. 1 Test, Code 11 Schematic, ECU (+B) Circuit (4-Cyl.). Scheme 70
No. 1 Test, Code 11 Flow Chart, ECU (+B) Circuit (4-Cyl.). Scheme 71
No. 1 Test, Code 11 Schematic, ECU (+B) Circuit (V6). Scheme 72
No. 1 Test, Code 11 Flow Chart (1 Of 4), ECU (+B) Ckt (V6). Scheme 73
No. 1 Test, Code 11 Flow Chart (2 Of 4), ECU (+B) Ckt (V6). Scheme 74
No. 1 Test, Code 11 Flow Chart (3 Of 4), ECU (+B) Ckt (V6). Scheme 75
No. 1 Test, Code 11 Flow Chart (4 Of 4), ECU (+B) Ckt (V6). Scheme 76
No. 2 Test (4-Cyl.) Code 12, 13, 14 Schematic, Ign & RPM Sig. Scheme 77
No. 2 Test (V6) Code 12, 13, 14 Schematic, Ign & RPM Signal. Scheme 78
No. 2 Test, Code 12, 13, 14 Flow Chart, Ign & RPM Signal. Scheme 79
No. 3 Test, Code 21 Schematic, O2 Sensor Circuit (V6). Scheme 80
No. 3 Test, Code 21 Flow Chart, O2 Sensor Circuit (V6). Scheme 81
No. 3 Test, Code 21, Testing O2 Sensor Circuit (V6). Scheme 82
No. 4 Test, Code 22 Schematic, Coolant Temp. Sensor Circuit. Scheme 83
No. 4 Test, Code 22 Flow Chart, Coolant Temp. Sensor Ckt. Scheme 84
No. 4 Test, Code 22, Testing Water Temp. Sens. Scheme 85
No. 5 Test, Code 24 Schematic, Air Temp. Sensor Circuit. Scheme 86
No. 5 Test, Code 24 Flow Chart, Air Temp. Sensor Circuit. Scheme 87
No. 5 Test, Code 24, Air Flow Meter Test. Scheme 88
No. 6 Test, Codes 25 & 26 Schematic, O2 Sensor Ckt (4WD). Scheme 89
No. 6 Test, Codes 25 & 26 Flow Chart, O2 Sensor Ckt (4WD). Scheme 90
No. 6 Test, Codes 25 & 26, Connectors E1 & T and E1, T & VF Test (4WD). Scheme 91
No. 7 Test, Codes 31 & 32 Schematic, Airflow Meter Signal. Scheme 92
No. 7 Test, Codes 31 & 32 Flow Chart, Airflow Meter Signal. Scheme 93
No. 7 Test, Codes 31 & 32, Airflow Meter Test. Scheme 94
No. 8 Test, Code 41 Schematic, TPS Signal (4-Cyl. W/O ECT). Scheme 95
No. 8 Test, Code 41 Flow Chart, TPS Signal (4-Cyl. W/O ECT). Scheme 96
No. 8 Test, Code 41, TPS Signal Test (4-Cyl. W/O ECT). Scheme 97
No. 8 Test, Code 41 Schematic, TPS Sig. (4-Cyl. W/ECT & V6). Scheme 98
No. 8 Test, Code 41 Flow Chart (1 of 3), TPS Signal (4-Cyl. W/ECT & V6). Scheme 99
No. 8 Test, Code 41 Flow Chart (2 of 3), TPS Signal (4-Cyl. W/ECT & V6). Scheme 100
No. 8 Test, Code 41 Flow Chart (3 of 3), TPS Signal (4-Cyl. W/ECT & V6). Scheme 101
No. 8 Test, Code 41, TPS Signal Test (4-Cyl. W/ECT & V6). Scheme 102
No. 9 Test, Code 43 Schematic, Starter Signal. Scheme 103
No. 9 Test, Code 43 Flow Chart, Starter Signal. Scheme 104
Test 10, Schematic, EGR System Circuit (Calif.). Scheme 105
Test 10, Flow Chart, EGR System Circuit (Calif.). Scheme 106
Test 10, EGR Gas Temp. Sens. Test (Calif.). Scheme 107
Test 11 Schematic, ECU Power Source (4-Cyl.). Scheme 108
Test 11 Flow Chart, ECU Power Source (4-Cyl.). Scheme 109
Test 12 Schematic, Injector Circuit Test (4-Cyl.). Scheme 110
Test 12 Schematic, Injector Circuit Test (V6). Scheme 111
Test 12 Flow Chart, Injector Circuit Test. Scheme 112
Test 13 Schematic, "CHECK ENGINE" Light Circuit. Scheme 113
Test 13 Flow Chart, "CHECK ENGINE" Light Circuit. Scheme 114
Test 14 Schematic, ISC Valve Circuit (4-Cyl.). Scheme 115
Test 14 Flow Chart, ISC Valve Circuit (4-Cyl.). Scheme 116
Test 14, ISC Valve Resistance Check (4-Cyl.). Scheme 117
Test 14 Schematic, ISC Valve Circuit (V6). Scheme 118
Test 14 Flow Chart, ISC Valve Circuit (V6). Scheme 119
Test 14, ISC Valve Check (V6). Scheme 120
Test 15 Schematic, A/C Switch Circuit. Scheme 121
Test 15 Flow Chart, A/C Switch Circuit. Scheme 122
AIRFLOW METER
Turn ignition off. Disconnect wiring connector from airflow meter. Note terminal identification. (Scheme 123) Using an ohmmeter, measure resistance between specified terminals. Replace airflow meter if not within specification. See AIRFLOW METER RESISTANCE SPECIFICATIONS table.
Scheme 123
| Application Terminals | Ohms | |
|---|---|---|
| E2-THA | ||
| 4°F (20°C) | 10,000-20,000 | |
| 32°F (0°C) | 4000-7000 | |
| 68°F (20°C) | 2000-3000 | |
| 104°F (40°C) | 900-1300 | |
| 140°F (60°C) | 400-700 | |
| E2-Vc | 200-400 | |
| E1-Fc | ||
| Measuring Plate Fully Closed | Infinity | |
| Measuring Plate Other Than Closed | 0 | |
| E2-Vs | ||
| Measuring Plate Fully Closed | 200-600 | |
| Measuring Plate Fully Open | 20-1200 | |
AIRFLOW METER RESISTANCE SPECIFICATIONS
Camry 2.0L
- Warm engine to normal operating temperature. Ensure idle speed is correct. Apply parking brake and place transaxle in Neutral. Install jumper wire between terminals "T" and "E1" of check connector located near left shock tower. (Scheme 124)through (Scheme 126).
- Note that engine RPM is maintained at 1000-1300 RPM for 5 seconds then returns to idle on Camry.
- If engine RPM was not within specification, disconnect ISC valve connector. Using ohmmeter, measure resistance between terminals "B +" and "ISC1" AND "ISC2". (Scheme 124)through (Scheme 126). Replace valve if resistance is not within 16-17 ohms.
Camry 2.5L
- Listen for "clicking" sound after engine is shut off. If no sound is heard, disconnect ISC valve connector.
- Note terminal identification. (Scheme 124)through (Scheme 126). Using an ohmmeter, check resistance between designated terminals. See «ISC VALVE RESISTANCE SPECIFICATIONS»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) table. ISC VALVE RESISTANCE SPECIFICATIONS Terminals Ohms B1 - S1 or S 10-30 B2 - S2 or S4 10-30
- To check valve operation, apply battery voltage to terminal "B1" and terminal "B2". (Scheme 123) Repeatedly ground terminals "S1", "S2", "S", "S4" and "S1" in sequence. Note that valve closes. (Scheme 124)through (Scheme 126).
- Apply battery voltage to terminals "B1" and "B2". Repeatedly ground terminals "S4", "S", "S2", "S1" and "S4" in sequence. Note that valve opens. Replace valve if it failed to operate properly.
Scheme 124
Scheme 125
Scheme 126
Turn ignition off and disconnect electrical connector at TPS. Note terminal identification. (Scheme 127)through (Scheme 129). Insert specified thickness feeler gauge between throttle stop screw and throttle ever. See TPS RESISTANCE SPECIFICATIONS table. Using an ohmmeter, check for resistance or continuity. Replace or adjust TPS if not within specification. See TPS RESISTANCE SPECIFICATIONS table.
Scheme 127
Scheme 128
Scheme 129
| Clearance In. (mm) | Terminal Value | Ohmmeter Reading | |
|---|---|---|---|
| 3S-FE (W/ECT) | |||
| 0 (0) | VTA & E2 | 200-800 | |
| .020 (.51) | IDL & E2 | 2300 or Less | |
| .028 (.71) | IDL & E2 | Infinity | |
| Fully Open | VTA & E2 | 3300-10,000 | |
| Fully Open | VC & E2 | 3000-7000 | |
| 3S-FE (W/O ECT) | |||
| .020 (.51) | IDL & E1 | Continuity | |
| .020 (.51) | PSW & E1 | No Continuity | |
| .035 (.89) | IDL & E1 | No Continuity | |
| .035 (.89) | PSW & E1 | No Continuity | |
| Fully Open | IDL & E1 | No Continuity | |
| Fully Open | PSW & E1 | Continuity | |
| 2VZ-FE | |||
| 0 (0) | VTA & E2 | 300-6300 | |
| .012 (.30) | IDL & E2 | 2300 or Less | |
| .028 (.71) | IDL & E2 | Infinity | |
| Fully Open | VTA & E2 | 3500-10,300 | |
| Fully Open | VC & E2 | 4250-8250 | |
TPS RESISTANCE SPECIFICATIONS
Disconnect switch connector. Note terminal identification. (Scheme 130) Using ohmmeter, check resistance between terminals "STA" & "STJ" at appropriate temperature. See COLD START INJECTOR TIME SWITCH SPECIFICATIONS table. Check resistance between terminal "STA" and ground. Replace switch if not within specification.
| Condition | Resistance - Ohms | |
|---|---|---|
| 3S-FE | ||
| Below 86°F (30°C) | 20-40 | |
| Above 104°F (40°C) | 40-60 | |
| To Ground | 20-80 | |
| 2VZ-FE | ||
| Below 59°F (15°C) | 25-45 | |
| Above 86°F (30°C) | 65-85 | |
| To Ground | 25-85 | |
COLD START INJECTOR TIME SWITCH SPECIFICATIONS
Scheme 130
Remove connector from sensor. Using ohmmeter, check resistance between sensor terminals. Replace sensor if resistance is not within specification at specified temperature. (Scheme 131)
Scheme 131
EGR TEMPERATURE SENSOR
Place threaded end of sensor and thermometer in container of oil. Attach ohmmeter to sensor terminals. Heat the oil and note the resistance at specified temperature. See EGR TEMPERATURE SENSOR SPECIFICATIONS table. Replace sensor if not within specification.
| Temperature | Ohms |
|---|---|
| 122 (50) | 69-89 |
| 212 (100) | 12-14 |
| 302 (150) | 3-4 |
EGR TEMPERATURE SENSOR SPECIFICATIONS
Camry 2VZ-FE (Calif. Models)
- Inspection is required when trouble code No. 27 exists. Clear trouble codes. See CLEARING TROUBLE CODES under «DIAGNOSIS & TESTING»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) in this article. Warm engine to normal operating temperature.
- Drive vehicle between 50 and 62 MPH for at least 5 minutes in 4th or 5th gear (M/T) or "D" range (A/T).
- On all models, fully depress accelerator pedal for at least 2 seconds. CAUTION: DO NOT exceed 62 MPH or trouble code will be canceled.
- Stop engine and turn ignition off. Repeat previous steps and note if trouble code No. 27 exists again. If trouble code exists again, check sub-oxygen sensor circuit for continuity, shorts or grounds. Replace sub-oxygen sensor if circuit is okay.
OXYGEN (O2) SENSOR HEATER
Disconnect sensor connector. Using ohmmeter, measure resistance between sensor terminals. Replace sensor if resistance is not within 5-6 ohms at 68°F (20°C).
Information not available at time of publication.
Scheme 132
- Warm engine to normal operating temperature. Connect an analog type voltmeter to appropriate EFI check connector terminal. (Scheme 132) Install jumper wire between appropriate check engine connector terminals. See «CHECK ENGINE CONNECTOR TERMINALS»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) table. CHECK ENGINE CONNECTOR TERMINALS Application Terminals Camry T (TE1) & E1
- Maintain engine speed at 2500 RPM and check the number of times voltmeter needle fluctuates in 10 seconds. See «VOLTMETER NEEDLE FLUCTUATION»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) table. If needle does not fluctuate at all, go to step 4). If needle fluctuations are less than amount specified, go to step 3). If needle fluctuations are as specified or more, oxygen sensor is okay. VOLTMETER NEEDLE FLUCTUATION Application Normal Fluctuations Camry 8 Times
- If needle fluctuations are less than amount specified, remove jumper wire at check engine connector, but keep voltmeter connected to EFI check connector terminals. Maintain engine speed at 2500 RPM (ensuring oxygen sensor is thoroughly warmed), and measure voltage at EFI check connector terminals. If voltage reading is 0 (zero), go to step 4). If voltage is more than 0 (zero) volts, replace main oxygen sensor and repeat step 1).
- Read and record diagnostic codes. See RETRIEVING TROUBLE CODES in «DIAGNOSIS & TESTING»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) in this article. Repair any codes that are nonrelated. If codes are relevant or are normal, remove jumper wire previously installed at check engine connector, but keep voltmeter connected to EFI check connector terminals.
- Maintain engine speed at 2500 RPM and measure voltage again. If voltage is 5 volts or more, go to next step. If voltage does not exist, disconnect PCV hose and measure voltage again. If voltage reading remains at 0 (zero), replace oxygen sensor and repeat step 1). If voltage is more than 0 (zero) volts, repair for an over rich condition.
- Unplug coolant temperature sensor connector. Connect a 4-8 ohm resistor across connector terminals. If resistor is not available, replace with new coolant temperature sensor. Repeat step 1) and measure voltage at terminals. If voltage is not present, replace the main oxygen sensor and repeat step 1). If needle fluctuations are less than specified after replacing the oxygen sensor, replace ECU.
Power Source
Turn ignition on. Disconnect turbocharging pressure sensor connector and measure voltage between terminals "VC" and "E2" of harness connector. (Scheme 133) Voltage should be 4-6 volts.
Scheme 133
Power Output
- Turn ignition on. Disconnect turbocharging pressure sensor vacuum hose from intake manifold. Connect voltmeter to terminals "PIM" and "E2" (pressure sensor) of ECU connector and measure output voltage under ambient atmospheric pressure.
- Attach a vacuum pump to turbocharging pressure sensor vacuum hose and apply vacuum in specified stages. (Scheme 134) Measure and record voltage readings for each stage of applied vacuum. See «VACUUM/VOLTAGE SPECIFICATIONS»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) table. Replace sensor if readings are not within specifications.
Scheme 134
| Applied Vacum In. Hg | Volts |
|---|---|
| 3.94 | .15-.35 |
| 7.87 | .4-.35 |
| 11.81 | .65-.85 |
| 15.75 | .9-1.1 |
| 19.69 | 1.15-11.35 |
VACUUM/VOLTAGE SPECIFICATIONS
TURBOCHARGING PRESSURE VACUUM SWITCHING VALVE (VSV)
- Using an ohmmeter, check continuity between both terminals of turbocharging pressure VSV connector. (Scheme 135) Replace VSV if no continuity exists.
- Check that no continuity exists between VSV case (body) and each terminal. If continuity exists, replace VSV.
- Check that air does not flow from pipe "E" to pipe "F". If air flows through from pipe "E" to pipe "F", replace VSV.
Scheme 135
Speed Sensor (Analog Type)
Remove combination meter from instrument cluster. Connect ohmmeter between proper terminals. (Scheme 136) See NO. 1 SPEED SENSOR TEST TERMINALS (ANALOG TYPE). Rotate meter shaft and note reading. Ohmmeter should deflect from 0 (zero) to infinity ohms as shaft is rotated.
| Application | Test Terminals |
|---|---|
| Camry | A & B |
NO. 1 SPEED SENSOR TEST TERMINALS (ANALOG TYPE)
Scheme 136
No. 1 Speed Sensor (Digital Type)
- Note terminal identification. (Scheme 137) Connect voltmeter between proper terminals. See «NO»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system__no-1-speed-sensor-digital-type). 1 SPEED SENSOR TEST TERMINALS (DIGITAL TYPE) table for proper terminals. It may be necessary to remove combination meter.
- Turn ignition on, with engine off. Voltmeter should deflect between specified voltage as meter shaft is rotated. See «NO 1 SPEED SENSOR TEST TERMINALS (DIGITAL TYPE)»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) table.
| Application | Test Terminals | Volt (1) Reading |
|---|---|---|
| Camry | 9 & 11 | 5 |
| (1) Voltage should occur 4 times per meter shaft rotation. | ||
| (1) | Voltage should occur 4 times per meter shaft rotation. |
NO 1 SPEED SENSOR TEST TERMINALS (DIGITAL TYPE)
Scheme 137
FUEL-CUT RPM
- Connect a tachometer to engine (to monitor needle fluctuations). Start engine and warm to operating temperature. Disconnect throttle position sensor connector from throttle position sensor. Short terminals IDL and E1 (or E2) on wire side of connector. (Scheme 138)and (Scheme 139).
- Gradually raise engine RPM. Fuel-cut operation can be checked by noting the fluctuation of tachometer needle. Fluctuation indicates fuel-cut system is being turned on and off. (Scheme 140) Check that fuel-cut points and fuel return points are within specifications. See «FUEL-CUT & FUEL RETURN RPM»(/toyota/camry/v20-1986-1991/remont/testing-diagnostics/#computer-control-system) table.
Scheme 138
Scheme 139
Scheme 140
| Model | Fuel-Cut Engine RPM | Fuel Return Engine RPM |
|---|---|---|
| 4-Cyl. | 1700 | 1300 |
| V6 | 1800 | 1200 |
FUEL-CUT & FUEL RETURN RPM
Disconnect switch connector. Note terminal identification. (Scheme 141) Using ohmmeter, check for continuity at specified terminals with gearshift in proper range. See NEUTRAL/START SWITCH SPECIFICATIONS table.
| Gearshift Position | Terminals | |
|---|---|---|
| 2VZ-FE | ||
| "R" | RL & C | |
| "N" | NL & C | |
| "2" | 2L & C | |
| "L" | LL & C | |
| 3S-FE | ||
| "N" | NL & C | |
| "2" | 2L & C | |
| "L" | LL & C | |
NEUTRAL/START SWITCH SPECIFICATIONS
Scheme 141
4-Cylinder Wiring Diagram. Scheme 142
V6 Wiring Diagram. Scheme 143
See also:
• TOYOTA ENGINE CODE
• NO