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DTC P0115, DTC P0117 OR DTC P0118 Lexus SC II

Testing & Diagnostics 3 illustrations ~476 words

Code Definitions

  1. DTC P0115: Engine Coolant Temperature Circuit
  2. DTC P0117: Engine Coolant Temperature Circuit Low Input
  3. DTC P0118: Engine Coolant Temperature Circuit High Input

Note. For information on engine immobilizer system, see COMPUTERIZED ENGINE CONTROLS in THEORY & OPERATION article.

CAUTIONIf ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES - LEXUS article.

Circuit Description

Engine Coolant Temperature (ECT) sensor is a thermistor that monitors coolant temperature. (Scheme 58) If DTC is set, ECM will operate in fail-safe mode. During fail-safe mode, engine coolant temperature is fixed at 176°F (80°C). DTC is set when ECM detects an open or short in ECT sensor circuit. Possible causes are

  1. Open or short in ECT sensor circuit.
  2. Faulty ECT sensor.
  3. Faulty ECM.

Scheme 58

Scheme 58
Scheme 58

Diagnostic Aids

After confirming DTC P0115, P0117 and P0118 use scan tool to access CURRENT DATA to confirm engine coolant temperature. If temperature displayed on scan tool is -40°F (-40°C), ECT sensor circuit may be open. If temperature displayed on scan tool is 284°F (140°C) or more, ECT sensor circuit may be shorted. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Scheme 59

Scheme 59: Diagnosis & Repair
Scheme 59: Diagnosis & Repair

Scheme 60

Scheme 60
Scheme 60
  1. Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Turn ignition on. Turn scan tool on. Using scan tool, monitor ECT sensor temperature. If temperature displayed is same as actual coolant temperature, problem is intermittent. If temperature displayed is -40°F (-40°C), go to next step. If temperature displayed is 284°F (140°C), go to step 4.
  2. Turn ignition off. Disconnect ECT sensor 2-pin connector. (Scheme 59) Turn the ignition switch ON. Connect terminals No. 1 and No. 2 of ECT sensor wire harness side connector. Read the engine coolant temperature value on the OBD-II scan tool or the hand-held tester. If temperature displayed is 284°F (140°C) or more, replace engine coolant temperature sensor. If not, go to next step.
  3. Turn ignition off. Disconnect ECT sensor connector. Turn ignition switch ON. Connect jumper wire between terminals THW and ETHW of the E4 ECM connector. (Scheme 60) Read the engine coolant temperature value on the OBD-II scan tool or the hand-held tester. If temperature displayed on scan tool is 284°F (140°C) or more, check for an open in wire between ECT sensor harness connector and ECM E4 connector. If temperature displayed on scan tool is not 284°F (140°C) or more, replace ECM and retest.
  4. Turn ignition off. Disconnect ECT sensor connector. (Scheme 59) Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), replace ECT sensor and retest. If temperature displayed is not -40°F (-40°C), turn ignition off and go to next step.
  5. Disconnect E4 connector from ECM. (Scheme 60) Turn ignition on. If temperature displayed is -40°F (-40°C), check for short in wire between ECT sensor and ECM E4 connector. If temperature displayed by scan tool is not -40°F (-40°C), replace ECM and retest.

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