The P1155 error code on Toyota vehicles indicates a potential issue with the heater circuit of the air-fuel ratio (A/F) sensor located upstream of the catalytic converter, for cylinder bank number 2 (the bank opposite the one containing cylinder number 1), sensor number 1. Several causes can trigger this code:
- Faulty air-fuel ratio (A/F) sensor, bank 2 sensor 1: The sensor itself might be malfunctioning.
- Wiring problems with the A/F sensor, bank 2 sensor 1: The wiring harness could be interrupted (open) or short-circuited.
- Poor electrical connection in the A/F sensor circuit, bank 2 sensor 1: A faulty electrical contact at the sensor connector.
- Faulty Engine Control Module (ECM): In rare cases, the engine computer could be the cause of the problem.
How to fix the P1155 code on a TOYOTA?
The first step is to carefully examine the possible causes mentioned above. Start with a visual inspection of the wiring harness and connectors associated with the air-fuel ratio sensor of bank 2, sensor 1. Look for any signs of damage to the wires and check the condition of the connector pins: ensure they are not broken, bent, pushed in, or corroded.
When is the P1155 code detected?
The P1155 code is recorded by the Engine Control Module (ECM) when it detects a malfunction in the heater circuit of the heated oxygen sensor (which is actually an air-fuel ratio sensor in this case).
Symptoms associated with the P1155 code:
The most common symptom is the illumination of the check engine light (or the “Service Engine Soon” warning light).
Meaning of the P1155 code in TOYOTA:
The air-fuel ratio (A/F) sensor must reach a minimum operating temperature of approximately 1200,∘F (approximately 650,∘C) to generate an accurate voltage signal. The faster the sensor reaches this temperature, the sooner it begins transmitting reliable information to the Engine Control Module (ECM).
To reach this temperature quickly, a heating element is integrated inside the air-fuel ratio sensor. The ECM controls this heating element based on signals from the engine coolant temperature and engine load. The ECM manages the heater circuit by allowing current to flow to ground.
The ECM monitors the voltage signal it receives from the heater circuit and determines the status of this circuit by comparing the measured voltage to the values specified by the manufacturer. A significant deviation from these values can trigger the P1155 error code.
