Engine Controls - Tests W/codes Toyota Tercel L40

INTRODUCTION

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed with self-diagnostics. If no fault codes or only pass codes are present after entering self-diagnostics, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).

Hard Failures

Hard failures cause CHECK ENGINE light to illuminate and remain on until problem is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, the vehicle runs but driveability will not be optimum.

Intermittent Failures

Intermittent failures may cause CHECK ENGINE light to flicker or illuminate and go out after the intermittent fault goes away. However, the corresponding trouble code will be retained in ECU memory. If related fault does not reoccur within a certain time frame, related trouble code will be erased from ECU memory. Intermittent failures may be caused by a sensor, connector or wiring related problem. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

Scheme 41

Scheme 42

1. Before retrieving codes, verify CHECK ENGINE light comes on with ignition on and engine off. The CHECK ENGINE light should go off when engine is started. If CHECK ENGINE light does not come on, see appropriate DIAGNOSTIC CIRCUIT CHECK under CODE CHARTS. If light remains on, system has detected a malfunction or abnormality.
2. Ensure battery voltage is greater than 11 volts and charging system is okay. Engine should be at normal operating temperature.
3. Apply parking brake. Shift transaxle to Neutral (M/T) or Park (A/T). Turn A/C and all accessories off. Close throttle valve.
4. Turn ignition on with engine off. Install jumper wire between terminals TE1 (or T) and E1 in engine check connector. (Scheme 41)
5. Count number of flashes from CHECK ENGINE light. If system is operating properly (with no codes), CHECK ENGINE light will flash continuously and evenly. (Scheme 42) NOTE: If CHECK ENGINE light will not flash diagnostic codes, see appropriate DIAGNOSTIC CIRCUIT CHECK under CODE CHARTS.
6. If a code exists, digits of code will flash at 1/2-second intervals, with a 1 1/2-second pause between first and second digits. (Scheme 42)
7. If more than one code is stored, a 2 1/2-second pause will occur before next code is flashed. Once all fault codes are displayed, a4 1/2-second pause will occur, then code(s) will be repeated.
8. Codes are displayed from the smallest to largest code. After codes are retrieved, remove jumper wire to exit diagnostic mode.

NOTES ON CODES

1. No other code will appear with Code 11.
2. When Codes 21, 25, 26, 27 and 71 initially happen, they will be temporarily stored in ECU memory, but CHECK ENGINE light will not come on. The second time code is detected, CHECK ENGINE light will then come on. This is referred to as the 2 trip detection logic.
3. CHECK ENGINE light will go off after malfunction is repaired, but codes (except 51 and 53) will remain in ECU memory until codes are cleared.

CLEARING CODES

1. After repairs are performed, clear ECU memory of all stored codes. To clear memory, turn ignition off. Remove proper fuse from main fuse block for approximately 30 seconds or more. See «MAIN FUSE BLOCK LOCATION»(/toyota/tercel/l40-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. See «CLEARING CODES»(/toyota/tercel/l40-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) table for proper fuse to be removed.
2. Depending on ambient temperature, fuse may need to be removed for more than 30 seconds. (Colder temperatures require longer time.) Install fuse and enter diagnostic mode to check for any codes that may not have cleared.
3. Codes can also be cleared by disconnecting vehicle battery. However, other memory functions (clock, radio, alarm, seats, etc.) will need to be reset.

MAIN FUSE BLOCK LOCATION

CLEARING CODES

ECU LOCATION

ECU LOCATION

SUMMARY

If no hard fault codes are present (or only pass codes), driveability symptoms exist or intermittent codes exist, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

Note. To determine a common cause for a code to be set, see CODE DIAGNOSTIC HINTS table.

CODE DIAGNOSTIC HINTS

TROUBLE CODE IDENTIFICATION CHARTS

TERCEL CODE IDENTIFICATION

DIAGNOSTIC CODE CHARTS

Note. All schematics and diagnostic flow charts are courtesy of Toyota Motor Sales, U.S.A., Inc.

ECU TERMINAL IDENTIFICATION

ECU Terminal Identification. Scheme 43

Diagnostic Circuit Check Schematic. Scheme 44

Diagnostic Circuit Check Flow Chart. Scheme 45

TEST NO. 1 - ECU POWER SOURCE

TEST NO. 1-ECU POWER SOURCE TROUBLE

Test No. 1 Schematic ECU Power Source. Scheme 46

Test No. 1 Flow Chart ECU Power Source. Scheme 47

TEST NO. 2 - ECU (+B) CIRCUIT

TEST NO. 2-ECU (+B) CIRCUIT TROUBLE

Test No. 2 Schematic ECU (+B) Circuit. Scheme 48

Test No. 2 Flow Chart ECU (+B) Circuit. Scheme 49

CODE 12, 13 - RPM SIGNAL

Code 12 is caused by loss of "G" or "NE" signal from distributor to ECU for at least 2 seconds after starter signal is received at ECU. Check distributor and ignition system components. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Ensure starter signal exists at ECU. See TERCEL TEST NO. 9 OR CODE 43.

Code 13 is caused by loss of "NE" signal from distributor to ECU when engine RPM exceeds 1500 RPM. Check distributor and ignition system components. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

Note. Diagnostic chart not available from manufacturer.

CODE 14/TEST NO. 3 - IGNITION SIGNAL

Note. To check ignition system components, see I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

CODE 14/TEST NO. 3-IGNITION SIGNAL TROUBLE

Code 14/Test No. 3 Schematic Ignition Signal. Scheme 50

Code 14/Test No. 3 Flow Chart Ignition Signal. Scheme 51

Code 21/Test No. 4 Schematic Oxygen Sensor Signal. Scheme 52

Code 21/Test No. 4 Flow Chart Oxygen Sensor Signal. Scheme 53

CODE 22/TEST NO. 5 - COOLANT TEMPERATURE SENSOR SIGNAL

Note. Water temperature sensor is also referred to as coolant temperature sensor.

CODE 22/TEST NO. 5-CTS SENSOR SIGNAL TROUBLE

Code 22/Test No. 5 Schematic Coolant Temperature Sensor Signal. Scheme 54

Code 22/Test No. 5 Flow Chart Coolant Temperature Sensor Signal. Scheme 55

CODE 24/TEST NO. 6 - INTAKE AIR TEMPERATURE SENSOR CIRCUIT

CODE 24/TEST NO. 5-IAT SENSOR SIGNAL TROUBLE

Code 24/Test No. 6 Schematic Intake Air Temp. Sensor Circuit. Scheme 56

Code 24/Test No. 6 Flow Chart Intake Air Temp. Sensor Circuit. Scheme 57

Probable Causes

1. Loose Engine Ground Bolt
2. Open E1 Circuit
3. Open Injector Circuit
4. Fuel Line Pressure (Blocked Injector)
5. Open Or Short In Oxygen Sensor Or Circuit
6. Ignition System
7. Coolant Temperature Sensor
8. Vacuum Sensor
9. EGR System
10. ECU

For oxygen sensor or circuit testing, see Code 21.

For injector or circuit testing, see TEST NO. 12.

Note. Diagnostic chart not available from manufacturer.

1. Loose Engine Ground Bolt
2. Open E1 Circuit
3. Short In Injector Circuit Or Injector
4. Fuel Line Pressure (Leaking Injector)
5. Open Or Short In Oxygen Sensor Or Circuit
6. Coolant Temperature Sensor
7. Vacuum Sensor
8. Compression Pressure
9. ECU

For oxygen sensor or circuit testing, see Code 21.

For injector or circuit testing, see TEST NO. 12.

Note. Diagnostic chart not available from manufacturer.

CODE 31/TEST NO. 7 - VACUUM SENSOR SIGNAL

CODE 31/TEST NO. 7-VACUUM SENSOR SIGNAL TROUBLE

Code 31/Test No. 7 Schematic Vacuum Sensor Signal. Scheme 58

Code 31/Test No. 7 Flow Chart Vacuum Sensor Signal. Scheme 59

CODE 41/TEST NO. 8 - THROTTLE POSITION SENSOR SIGNAL

CODE 41/TEST NO. 8-TPS SENSOR SIGNAL TROUBLE

Code 41/Test No. 8 Schematic Throttle Position Sensor Signal. Scheme 60

Code 41/Test No. 8 Flow Chart, Terminals IDL - E2 Throttle Position Sensor Signal. Scheme 61

Code 41/Test No. 8 Flow Chart, Terminals VCC - E2 Throttle Position Sensor Signal. Scheme 62

Code 41/Test No. 8 Flow Chart, Terminals VTA - E2 Throttle Position Sensor Signal. Scheme 63

1. Open or Short in Vehicle Speed Sensor or Circuit
2. ECU Defective

Note. Diagnostic chart not available from manufacturer.

CODE 43/TEST NO. 9 - STARTER SIGNAL

CODE 43/TEST NO. 9-STARTER SIGNAL TROUBLE

Code 43/Test No. 9 Schematic Starter Signal. Scheme 64

Code 43/Test No. 9 Component Diagram Starter Signal. Scheme 65

Code 43/Test No. 9 Flow Chart Starter Signal. Scheme 66

1. A/C Switch or Switch Circuit
2. Accelerator Pedal or Cable
3. Neutral/Start Switch or Switch Circuit
4. Throttle Position Sensor IDL Circuit
5. ECU

To check throttle position sensor or circuit, see Code 41

Note. To check A/C switch signal, use the following procedure.

CODE 51/TEST NO. 10-SWITCH SIGNAL TROUBLE

Code 51/Test No. 10 Schematic Switch Signal. Scheme 67

Code 51/Test No. 10 Flow Chart Switch Signal. Scheme 68

Code 71/Test No. 11 Schematic EGR System Malfunction. Scheme 69

Code 71/Test No. 11 Flow Chart EGR System Malfunction. Scheme 70

TEST NO. 12 - INJECTOR CIRCUIT

TEST NO. 12-INJECTOR CIRCUIT TROUBLE

Test No. 12 Schematic Injector Circuit. Scheme 71

Test No. 12 Flow Chart Injector Circuit. Scheme 72

TEST NO. 13 - CHECK ENGINE LIGHT CIRCUIT

TEST NO. 13-CHECK ENGINE LIGHT CIRCUIT TROUBLE

Test No. 13 Schematic Check Engine Light Circuit. Scheme 73

Test No. 13 Flow Chart Check Engine Light Circuit. Scheme 74

See also:
• MAIN FUSE BLOCK LOCATION
• 12 & 13
• 14
• 22
• 24
• 31
• 41
• 43