Code Definitions
- DTC P0136: Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)
- DTC P0156: Oxygen Sensor Circuit Malfunction (Bank 2 Sensor 2)
Note. For information on engine immobilizer system, see COMPUTERIZED ENGINE CONTROLS in THEORY & OPERATION article.
| CAUTION | If 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. |
Note. Bank No. 1 refers to bank which includes cylinder No. 1. Bank No. 2 refers to bank without cylinder No. 1. Heated oxygen sensor No. 1 refers to sensor closest to engine block. Heated oxygen sensor No. 2 refers to sensor furthest away from engine block.
Circuit Description
The oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses this input signal to determine fuel injection system operation. Sensors include heater.
DTC P0136 is for bank 1, sensor 2. DTC P0156 is for bank 2, sensor 2. DTC is set when sensor voltage remains at .4 volt or more or .5 volt or less during vehicle operation at 19 MPH or more, once engine is at normal operating temperature. Possible causes are
- Open or short in heated oxygen sensor circuit.
- Faulty heated oxygen sensor.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.
Scheme 76
Scheme 77
- Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-151781-S29975222372003010800000) under SELF-DIAGNOSTIC SYSTEM. If any other codes are displayed other than DTC P0136 or P0156, diagnose and repair those codes first. If only DTC P0136 or P0156 are displayed, go to next step.
- Disconnect the H15 and H16 heated oxygen sensor connectors. Disconnect the E5 ECM connector. (Scheme 76)and (Scheme 77). Check continuity between the wire harness side connectors. See «HO2S/ECM CONTINUITY CHECK»(ref-151781-S20741528952003022100000) table. Repair wiring as necessary. If wiring harness is okay, go to next step. HO2S/ECM CONTINUITY CHECK Terminals No. Specification OX (H15-4) - OXL2 (E5-28) Continuity HT (H15-2) - HTL2 (E5-7) Continuity OX (H16-4) - OXR2 (E5-17) Continuity HT (H16-2) - HTR2 (E5-8) Continuity OX (H15-4) Or OXL2 (E5-28) - E1 (E3-7) No Continuity HT (H15-2) Or HTL2 (E5-7) - E1 (E3-7) No Continuity OX (H16-4) Or OXR2 (E5-17) - E1 (E3-7) No Continuity HT (H16-2) Or HTR2 (E5-8) - E1 (E3-7) No Continuity
- Connect scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Start and warm engine to normal operating temperature. Monitor bank 1 and 2, sensor 2. Raise engine speed to 2500 RPM for 3 minutes. Return engine to idle. Quickly raise engine speed to 4000 RPM 3 times. Voltage should fluctuate from.4 volt or less to.5 volt or more. If voltage responds correctly, check wiring harness connections. Problem may be intermittent. If voltage does not respond correctly, replace appropriate oxygen sensor and retest.