DTC P0134 OR DTC P0154 Lexus SC II

Code Definitions

1. DTC P0134: Oxygen Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
2. DTC P0154: Oxygen Sensor Circuit No Activity Detected (Bank 2 Sensor 1)

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

Note. Bank No. 1 refers to bank that includes cylinder No. 1. Bank No. 2 refers to bank without cylinder No. 1. Sensor No. 1 refers to sensor closest to engine block.

Circuit Description

To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a 3-way catalytic converter is used. But for the most efficient use of the 3-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio. The heated oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This is used to detect the oxygen concentration in the exhaust gas and provide the ECM with feedback to control the air-fuel ratio. When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases. And the heated oxygen sensor informs the ECM of the LEAN condition (small electromotive force of greater than 0.45 volt). When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas is reduced, and the heated oxygen sensor informs the ECM of the RICH condition (large electromotive force is greater than 0.45 volt). The ECM judges by the electromotive force from the heated oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if the malfunction of the oxygen sensor causes an output of abnormal electromotive force, the ECM becomes unable to perform the accurate air-fuel ratio control. The main heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (temperature of the exhaust gas is low), current flows to the heater in order to heat the sensor for the accurate oxygen concentration detection.

DTC P0134 is for bank 1, sensor 1. DTC P0154 is for bank 2, sensor 1. DTC is set when engine is warmed up and idling and ECM detects a response time of one second or more for sensor to change from rich to lean, or lean to rich. Possible causes are

1. Open or short in oxygen sensor circuit.
2. Faulty heated oxygen sensor.
3. Air induction system fault.
4. Improper fuel system pressure.
5. Fuel injectors.
6. Faulty ECM.

Diagnostic Aids

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Scheme 74

Scheme 75

1. Retrieve trouble codes. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-151781-S29975222372003010800000) under SELF-DIAGNOSTIC SYSTEM. If any other codes are displayed other than DTC P0134 or P0154, diagnose and repair those codes first. If only DTC P0134 or DTC P0154 is displayed, go to next step.
2. Warm up the engine to the normal operating temperature above 169°F (75°C). Using scan tool, read the voltage output of the heated oxygen sensor when the engine is suddenly raced. Perform a quick racing to 4000 RPM 3 times using the accelerator pedal. If heated oxygen sensor outputs a RICH signal (0.45 volts or more) at least once, go to step 10. If not, go to next step.
3. Check connection of PCV hose. Repair as necessary. If okay, go to next step.
4. Disconnect the H9, H10, H15 and H16 heated oxygen sensor connectors. (Scheme 74) Disconnect the E3, E4 and E5 ECM connectors. (Scheme 75) Check the continuity between wire harness side connectors. See «HO2S/ECM CONTINUITY CHECK»(ref-151781-S24872636802003022100000) table. If okay, go to next step. If not okay, repair or replace harness or connector as necessary. HO2S/ECM CONTINUITY CHECK Terminals No. Specification OX (H9-3) - OXL1 (E3-28) Continuity HT (H9-1) - HTL (E3-9) Continuity OX (H10-3) - OXR1 (E4-28) Continuity HT (H10-1) - HTR (E4-30) Continuity 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 (H9-3) Or OXL1 (E3-28) - E1 (E3-7) No Continuity HT (H9-1 ) Or HTL (E3-9) - E1 (E3-7) No Continuity OX (H10-3) Or OXR1 (E4-28) - E1 (E3-7) No Continuity HT (H10-1) Or HTR (E4-30) - E1 (E3-7) No 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 (H1-26) Or HTR2 (E5-8) - E1 (E3-7) No Continuity
5. Check whether misfire has occurred or not by monitoring DTC and data list. Performing troubleshooting for misfire as necessary. If okay, go to next step.
6. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
7. Check fuel pressure. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ) and remain at 21 psi (1.5 kg/cm 2 ) for 5 minutes after engine has stopped. If fuel pressure is not within specification, replace fuel pump. If fuel pressure is within specification, go to next step.
8. Check fuel injectors. see scheme 42 Injector volume should be 3.7-4.5 cu. in. (60-73 cm 3 ) per 15 seconds. Difference between each injector should be.6 cu. in. (13 cm 3 ) or less. If problem exists, repair as necessary. If problem does not exist, replace suspect heated oxygen sensor.
9. Check for exhaust system leak. Repair as necessary. If okay, replace heated oxygen sensor.
10. Perform confirmation test drive, then go to next step. See «CONFIRMATION DRIVING PATTERN»(ref-151781-S21893087882003010800000).
11. Check if DTC P0134 or P0154 are output. If not, go to next step. If yes, check and replace ECM.
12. Check if vehicle ran out of fuel in the past. If not, problem is intermittent. If yes, DTC is caused by vehicle running out of fuel.