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2004 Jeep Wrangler P0155 O2 Sensor Code: Diagnosis and Repair Guide

Model: 2004 Jeep Wrangler Fault Code: P0155 Posted: 2010-01-06 13:18

I own a 2004 Jeep Wrangler and recently noticed the Check Engine Light (CEL) came on overnight. After connecting a code reader at AutoZone, I received fault code P0155. The light has remained on since then and won't turn off. Although the issue appeared suddenly, we've been experiencing unusually cold temperatures (upper 30s), and I park my vehicle outside during the day. Could this environmental factor be contributing to the problem? I'm seeking advice on what steps to take for a proper diagnosis and repair of this code from a technical standpoint.

Related fault codes
P0155
Comments (2)
Anonymous 2010-01-06 13:52

P0155 indicates an O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1). While the issue may point to a faulty upstream oxygen sensor on Bank 1, it's important to first verify the circuit integrity—check for proper power and ground connections, as well as inspect wiring harnesses and related fuses. Before replacing the sensor, ensure that the electrical circuit is functioning correctly. If the sensor is indeed defective, it’s recommended to use a factory-original part from the dealer, as aftermarket sensors may not meet OEM specifications and could cause persistent code errors. Always verify compatibility with your vehicle's VIN for optimal performance.

Anonymous 2010-01-06 22:17

If you can't access a dealership for an original NTK oxygen sensor—NTK is the factory supplier of O2 sensors for Jeep and many domestic vehicles—consider using a genuine NTK part. These are typically more expensive than aftermarket options, but they are specifically designed to work with your vehicle's engine control module (PCM). Avoid using Bosch sensors; their heater element has incorrect resistance values, which can cause the PCM to cycle the sensor excessively while trying to maintain proper heating. This leads to a persistent P0155 code and continued illumination of the Check Engine Light. For accurate part matching, consult your vehicle's VIN with a dealer or authorized service center.