Engine Controls - Tests W/codes - Except Obd-Ii: Other Lexus GS I

HARD FAILURES

Hard failures cause Malfunction Indicator Light (MIL) 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 trouble code charts. If a sensor fails, Electronic Control Module (ECM) will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, vehicle runs but driveability will not be optimum.

Note. The MIL may also be referred to as the CHECK ENGINE light. The MIL may not illuminate when certain failures occur (such as faulty starter signal or A/C switch signal) or if certain trouble codes are set.

INTERMITTENT FAILURES

Intermittent failures may cause MIL to flicker or glow and go out after intermittent fault goes away. Corresponding trouble code will be retained in ECM memory (except for Codes 16, 43, 51 and 53). Codes must be erased from memory after repair has been made. Intermittent failures may be caused by sensor, connector or wiring related problems. Refer to INTERMITTENTS text accompanying each test (as applicable).

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed with self-diagnostics. If no fault codes are present after entering self-diagnostics, proceed to appropriate TESTS W/O CODES article.

RETRIEVING CODES

Note. Diagnostic trouble codes may be retrieved using Lexus scan tester or Malfunction Indicator Light (MIL). Two modes are available for retrieving codes. Normal Mode is used to retrieve trouble codes from Engine Control Module (ECM) to determine problem area. Test Mode is used to check for trouble codes when operating vehicle to simulate conditions in which trouble code was set. Test mode contains a higher sensing ability to detect malfunctions. Test Mode helps determine malfunctions caused by poor electrical connections, which are difficult to determine using Normal Mode.

Lexus Scan Tester

All models are equipped with 2 Data Link Connectors (DLCs). Data Link Connector No. 1 (DLC1) is located in engine compartment. Data Link Connector No. 2 (DLC2) is located under left side of instrument panel. (Scheme 30) Codes can be retrieved by using DLC1 or D LC2. Connect scan tester to DLC1 or DLC2. Using scan tester manufacturer's instructions, retrieve trouble codes.

Scheme 30

Scheme 31

1. Normal mode is used for routine testing of vehicle. Before retrieving trouble code(s), verify MIL on instrument panel comes on with ignition on and engine off. The MIL light should go off when engine is started.
2. If MIL does not come on with ignition on and engine off, check bulb circuit on instrument panel and wiring circuit between MIL and ECM. See appropriate wiring diagram in «WIRING DIAGRAMS»(ref-21772) article. If MIL remains on, self-diagnostic system has detected a malfunction or abnormality.
3. Ensure battery voltage is at least 11 volts, throttle valve is fully closed, transaxle/transmission is in Neutral, all accessories are off and parking brake is applied.
4. All models are equipped with 2 Data Link Connectors (DLCs). Data Link Connector No. 1 (DLC1) is located in engine compartment. Data Link Connector No. 2 (DLC2) is located under left side of instrument panel. (Scheme 30) Codes can be retrieved by using D LC1 or DLC2.
5. To retrieve codes, turn ignition on. DO NOT start engine. Using a jumper wire, connect terminals E1 and TE1 together either on DLC1 or DLC2. (Scheme 31) Count number of flashes from Malfunction Indicator Light (MIL).
6. If MIL flashes 2 times every second, system is functioning properly (no codes present). This is known as a normal condition. If a diagnostic code is displayed, first group of flashes will indicate first digit of a 2-digit diagnostic code. After a 1.5 second delay, second group of flashes will indicate second digit of diagnostic code.
7. If more than one code is stored, a 2.5 second delay will occur between diagnostic codes. After all diagnostic codes have been displayed, a 4.5 second delay will occur and then codes will be repeated until jumper wire connecting terminals E1 and TE1 is disconnected. Diagnostic codes will display from smallest to largest number.
8. Identify and record diagnostic trouble codes. After trouble codes are retrieved, remove jumper wire to exit Normal Mode. See «NOTES ON TROUBLE CODES»(ref-21749-S27653218752001010300000). For additional information on trouble codes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-21749-S05363343442001010300000) table and appropriate DIAGNOSTIC TROUBLE CODE IDENTIFICATION table. After reading diagnostic trouble code definition and identification, perform appropriate diagnostic trouble code chart. To clear codes, see «CLEARING CODES»(ref-21749-S33568400162001010300000).

MALFUNCTION INDICATOR LIGHT (MIL) DOES NOT FLASH

1. Turn ignition on. Measure voltage between terminal E1 and terminals TE1 and TE2 of Data Link Connectors (DLCs) No. 1 and 2. (Scheme 31) Use terminal E1 as ground. If voltage is 9-14 volts, replace Electronic Control Module (ECM). If voltage is not 9-14 volts, go to next step.
2. Check continuity between ground and terminal E1 of DLCs No. 1 and 2. If continuity does not exist, repair open in wiring harness. If continuity exists, go to next step.
3. Check for an open or short in wiring harness between ECM and DLCs No. 1 and 2. Repair or replace wiring harness as necessary. If wiring harness is okay, check and replace ECM as necessary. See COMPUTERIZED ENGINE CONTROLS in «SYSTEM/COMPONENT TESTS»(ref-21748) article.

CLEARING CODES

1. Turn ignition off. Remove EFI fuse for at least 10 seconds. Fuse is a 20-amp fuse on GS300. Fuse is located in junction block No. 2 in left front engine compartment.
2. Codes can also be cleared by disconnecting negative battery cable. After clearing codes, recheck for codes to ensure codes have been cleared. If same code appears, trouble area has not been repaired properly.

Note. If disconnecting negative battery cable to clear codes, clock and radio memory systems will also be cleared.

SUMMARY

If no hard fault codes are present, driveability symptoms exist or intermittent codes exist, proceed to INTERMITTENTS text accompanying each test (as applicable).

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

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

CODE 21 - MAIN O2 SENSOR CKT (FEDERAL - FRONT O2 SENSOR)

Note. After repairs are completed, perform TROUBLE CODE DETECTION DRIVING PATTERN TEST.

Code 21 Front Oxygen Sensor Flow Chart (GS300 Federal) Main O2 Sensor Circuit (Front O2 Sensor). Scheme 32

CODE 28 - MAIN O2 SENSOR CKT (FEDERAL - REAR O2 SENSOR)

Note. After repairs are completed, perform TROUBLE CODE DETECTION DRIVING PATTERN TEST.

CODE 21 - MAIN O2 SENSOR CKT (GS300 CALIF. - FRONT O2 SENSOR)

Note. After repairs are completed, perform TROUBLE CODE DETECTION DRIVING PATTERN TEST.

Code 21 Flow Chart - 1 Of 2 (GS300 Calif.) Code 21 - Main O2 Sensor Circuit (Front O2 Sensor). Scheme 33

Code 21 Flow Chart - 2 Of 2 (GS300 Calif.) Code 21 - Main O2 Sensor Circuit (Front O2 Sensor). Scheme 34

Code 21 Trouble Code Detection Test (GS300 Calif.) Code 21 - Main O2 Sensor Circuit (Front O2 Sensor). Scheme 35

CODE 28 - MAIN O2 SENSOR CKT (GS300 CALIF. - REAR O2 SENSOR)

Note. After repairs are completed, perform TROUBLE CODE DETECTION DRIVING PATTERN TEST.

Code 22 Flow Chart Engine Coolant Temperature Sensor Circuit. Scheme 36

Code 24 Flow Chart Intake Air Temperature Sensor Circuit. Scheme 37

CODE 25 - AIR/FUEL RATIO MALFUNCTION (LEAN)

Note. After repairs are completed, perform TROUBLE CODE DETECTION DRIVING PATTERN TEST.

Code 25 Flow Chart (1 Of 3) Air/Fuel Ratio Malfunction (Lean). Scheme 38

Code 25 Flow Chart (2 Of 3) Air/Fuel Ratio Malfunction (Lean). Scheme 39

Code 25 Flow Chart (3 Of 3) Air/Fuel Ratio Malfunction (Lean). Scheme 40

Code 25 Trouble Code Detection Test Open Or Short In Main Heated O2 Sensor. Scheme 41

Code 25 Trouble Code Detection Test Open Or Short In Injection Circuit, Injector Leakage Or Blockage. Scheme 42

CODE 26 - AIR/FUEL RATIO MALFUNCTION (RICH)

Note. After repairs are completed, perform TROUBLE CODE DETECTION DRIVING PATTERN TEST.

Code 27 Flow Chart (1 Of 2) (GS300 Calif.) Sub-Oxygen Sensor Circuit. Scheme 43

Code 27 Flow Chart (2 Of 2) (GS300 Calif.) Sub-Oxygen Sensor Circuit. Scheme 44

Code 27 Trouble Code Detection Test (GS300 Calif.) Sub-Oxygen Sensor Circuit. Scheme 45

Code 31 Flow Chart (1 Of 2) Low Airflow Meter Voltage. Scheme 46

Code 31 Flow Chart (2 Of 2) Low Airflow Meter Voltage. Scheme 47

Code 35 Flow Chart Barometric Pressure Sensor Circuit. Scheme 48

Code 41 Flow Chart (1 Of 2) Throttle Position Sensor Signal. Scheme 49

Code 41 Flow Chart (2 Of 2) Throttle Position Sensor Signal. Scheme 50

Code 42 Flow Chart Vehicle Speed Sensor (VSS) Signal Circuit. Scheme 51

Code 43 Flow Chart Starter Signal. Scheme 52

Code 51 Flow Chart (1 Of 2) Switch Condition Signal. Scheme 53

Code 51 Flow Chart (2 Of 2) Switch Condition Signal. Scheme 54

Code 52, 53 & 55 Flow Chart (1 Of 2) Knock Sensor Circuit. Scheme 55

Code 52, 53 & 55 Flow Chart (2 Of 2) Knock Sensor Circuit. Scheme 56

Code 52, 53 & 55 Diag. Trouble Code Detection Test Knock Sensor Circuit. Scheme 57

Code 71 Flow Chart (1 Of 2) EGR System Malfunction. Scheme 58

Code 71 Flow Chart (1 Of 2) EGR System Malfunction. Scheme 59

Code 71 Diag. Trouble Code Detection Test EGR System Malfunction. Scheme 60

Code 78 Flow Chart (1 Of 2) Fuel Pump Control Circuit. Scheme 61

Code 78 Flow Chart (2 Of 2) Fuel Pump Control Circuit. Scheme 62

If no hard fault codes are present, driveability symptoms exist or intermittent codes exist, proceed to INTERMITTENTS under INTRODUCTION . If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES in the BASIC TESTING article, proceed with self-diagnostics. If no fault codes are present after entering self-diagnostics, proceed to appropriate TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.