← Back to list

1999 Toyota RX300 Check Engine Codes P1153 and P1155 - Causes and DIY Fix Guide

Model: 1999 RX300 Fault Code: P1153 Posted: 2006-10-30 09:03

I'm experiencing two OBD-II diagnostic codes on my 1999 Toyota RX300: P1153 (Air/Fuel Ratio Sensor Circuit Response Malfunction - Bank 2 Sensor 1) and P1155 (Air/Fuel Ratio Sensor Heater Circuit Malfunction - Bank 1 Sensor 1). The check engine light has been on for about two months, but the car runs smoothly with no performance issues or changes in fuel economy. Questions: Q1: How are these two codes related? What are the most likely causes? Q2: Is this a safety concern (can it be addressed safely later)? Q3: Can this issue be resolved by a do-it-yourselfer with basic mechanical knowledge? My vehicle has 107,000 miles on it. I'm new to automotive forums and appreciate any guidance or technical insights. Thank you for your help. Daniel

Related fault codes
P1153P1155
Comments (2)
Anonymous 2006-10-30 12:34

The MAF (Mass Airflow) sensor is a common culprit in these codes, especially on older RX300 models. A dirty or faulty MAF can cause incorrect air/fuel ratio readings, triggering both P1153 and P1155.

Anonymous 2006-10-30 14:21

Oxygen (O2) sensors are also frequently involved in these faults. Specifically, Bank 1 Sensor 1 and Bank 2 Sensor 1 may be failing or providing inaccurate data due to contamination or age, which can lead to heater circuit malfunctions and response issues.