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Engine Controls - Tests W/codes: Other Lexus SC I

Testing & Diagnostics 1 illustration ~982 words

TWO-TRIP DETECTION LOGIC

When a malfunction initially occurs, Diagnostic Trouble Code (DTC) will be temporarily stored in ECM memory, but MIL on instrument panel will not illuminate. The second time malfunction is detected, MIL on instrument panel will illuminate, provided ignition is turned off and then back on after first malfunction was detected. This is referred to as the 2-Trip Detection Logic and only applies to specified DTCs. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table under SELF-DIAGNOSTIC SYSTEM.

Note. When road testing vehicle in CHECK mode (Lexus scan tester only), the Two Trip Detection Logic will not function. Also, MIL will illuminate first time a malfunction is detected.

DATA LINK CONNECTOR

OBD-II regulations (SAE J-1850) standardizes Data Link Connector (DLC) configurations. On all models, DLC No. 3 connector is located in fuse box at lower left of instrument panel.

FREEZE-FRAME DATA

The ECM records engine operating condition when a misfire, fuel trim (mixture) malfunction or other malfunction (fuel system, calculated load, coolant temperature, fuel trim (mixture), engine speed, vehicle speed, etc.) exists. If more than one fault is detected, only data from the first malfunction is recorded. Recorded data is useful for determining conditions in which the malfunction occurs.

NORMAL Mode Code Retrieval

  1. Connect scan tester to Data Link Connector (DLC) No. 3. (Scheme 11) DLC No. 3 is located in fuse box at lower left of instrument panel. Turn ignition on with engine off. Turn scan tester on. Using scan tester manufacturer's instructions, check for DTCs and freeze-frame data.
  2. If scan tester displays UNABLE TO CONNECT TO VEHICLE, DLC No. 3 must be checked. See DLC NO. 3 INSPECTION under SCAN TESTER PROBLEMS. If scan tester does not display UNABLE TO CONNECT TO VEHICLE, go to next step.
  3. Record any DTCs and freeze-frame data displayed for system diagnosis. If driveability problem exists and no DTCs are present, go to TROUBLE SHOOTING - NO CODES article for diagnosis bysymptom.
  4. If any DTCs are present, perform appropriate circuit test in appropriate SELF-DIAGNOSTICS article. See «DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION»(ref-22023-S16408327382001010300000) table. For more information on freeze-frame data, see «FREEZE-FRAME DATA»(ref-22023-S03602575552001010300000) under INTRODUCTION. For information on 2-trip detection logic codes, see «TWO-TRIP DETECTION LOGIC»(ref-22023-S30565741382001010300000) under INTRODUCTION.
  5. After repairs for DTC have been completed, DTCs must be cleared from ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-22023-S04919415712001010300000).

Scheme 11

Scheme 11
Scheme 11

CHECK Mode Code Retrieval (Lexus Scan Tester Only)

  1. Ensure vehicle battery is fully charged. Apply parking brake. Shift transmission/transaxle into Neutral (M/T) or Park (A/T). Turn A/C and all accessories off. Ensure throttle is in idle position.
  2. Turn ignition off. Connect scan tester to Data Link Connector (DLC) No. 3. (Scheme 11) DLC No. 3 connector is located in fuse box at lower left of instrument panel. Turn ignition on with engine off. Turn scan tester on.
  3. Switch scan tester from NORMAL mode to CHECK mode. CHECK mode is operational if MIL on instrument cluster flashes. Start engine. Ensure MIL goes off. Try to simulate conditions of driveability complaint described by customer. NOTE: If ignition is turned from ON to ACC or OFF position, all DTCs and freeze-frame data will be erased. DO NOT switch modes until all DTCs and freeze-frame data are recorded.
  4. Record any DTCs and freeze-frame data displayed for system diagnosis. If driveability problem exists and no codes are present, go to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom.
  5. If any DTCs are present, perform appropriate circuit test. See «DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION»(ref-22023-S16408327382001010300000) table. For more information on freeze-frame data, see «FREEZE-FRAME DATA»(ref-22023-S03602575552001010300000) under INTRODUCTION. For information on 2-trip detection logic codes, see «TWO-TRIP DETECTION LOGIC»(ref-22023-S30565741382001010300000) under INTRODUCTION.
  6. After repairs for DTC have been completed, DTC must be cleared from ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-22023-S04919415712001010300000).

SUMMARY

If no diagnostic trouble codes are present, driveability symptoms exist or intermittents exist, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent procedures.

CIRCUIT TESTS

Note. Before performing any diagnostic circuit test, followw appropaite diagnostic flow. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM. For component location, see appropriate illustration in THEORY & OPERATION article.

Condition

Following conditions continue with engine speed of 900 RPM or less

  1. Closed throttle position switch in ON position.
  2. MAF sensor output is more than 2.2 volts.

DTC is set when sensor temperature is 86°F (30°C) or less for at least 20 minutes of engine operation. Possible causes are

  1. ECT sensor.
  2. Faulty cooling system.

DTC is set when TP sensor voltage is out of range. Possible cause is

  1. TP sensor.

DTC is set when ECM detects a response time of one second or more from sensor to change from rich to lean, or lean to rich. Possible cause is

  1. Heated oxygen sensor.

DTC is set when either of the following conditions is present

  1. Sensor heater current draw exceeds 2 amps, or voltage drop for heater circuit is more than 5 volts.
  2. Sensor heater current draw is .25 amp or less.

Possible causes are

  1. Heated oxygen sensor open or short circuit.
  2. Heated oxygen sensor heater.
  3. ECM.

DTC is set when bank No. 1, sensor No. 2 voltage remains at .4 volt or more or .5 volt or less during vehicle operation (31 MPH or more), once engine is at normal operating temperature. Possible cause is

  1. Heated oxygen sensor.

DTCS P0301-P0306 - CYLINDERS NO. 1-6 MISFIRE DETECTED

Note. When 2 or more codes for a misfiring cylinder are recorded repeatedly, but DTC P0300 is not recorded, it indicates that misfires were detected and stored into ECM memory at different times.

Two conditions can cause code to set. These are

  1. During any particular 200 revolutions of engine, misfiring is detected which can cause catalytic converter overheating and/or damage.
  2. During any particular 1000 revolutions of engine, misfiring is detected which can cause a deterioration in emission levels.

For possible causes, see DTC P0300 - RANDOM MISFIRE DETECTED.

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