How is fault code P0155 fixed?

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Read all stored and pending codes first. If P0155 turns up alongside its Bank 1 twin P0135, suspect a shared fuse or earth rather than two dead sensors at once 2. Pull the fuse for the oxygen sensor heater circuit and check it. A blown fuse is the cheapest fix you'll find and people skip straight past it 3. Get under the car and eyeball the sensor, its loom, and the connector for melted insulation, corrosion, bent pins, or water sitting in the plug 4. With the ignition on, back-probe the connector and check you're getting roughly 12V on the heater supply. No voltage points at the wiring or fuse, not the sensor 5. Measure resistance across the heater terminals on the sensor side. You're looking for somewhere around 2 to 15 ohms depending on the make. An open reading means the element is gone 6. Clean up and tighten any earth connections you find looking tatty before you spend money on parts

O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)

Jump to the fix

Severity

Medium

Can I keep driving?

Usually drivable, but get it diagnosed without delay.

First step

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Read all stored and pending codes first. If P0155 turns up alongside its Bank 1 twin P0135, suspect a shared fuse or earth rather than two dead sensors at once 2. Pull the fuse for the oxygen sensor heater circuit and check it.

PPowertrain
0Generic code
1Fuel / Air
55Sequence number

What does it mean?

The upstream oxygen sensor (O2S) is located ahead of the catalytic converter. It is used to determine the concentration of oxygen in the exhaust gas. This information is used by the PCM to control the engine air/fuel mixture. The sensor compares amount of oxygen in the exhaust to the surrounding air (there is an opening in the sensor that is exposed to the atmosphere). It generates a corresponding voltage which is transmitted to the PCM. The PCM then controls injector pulse based on this value.

Modern vehicles use a heated oxygen sensor (HO2S). These sensors contain a heating element that brings the sensor to operating temperature faster. This allows the PCM to use the signals input sooner, for more precise fuel control and reduced emissions. The heater circuit is energized through a relay that closes when the engine is cranked. The PCM monitors the heater circuit and will turn on the check engine light if it finds a problem.

Code P0155 stands for Oxygen O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1). This indicates the PCM has detected a problem with the bank 2 oxygen sensor. Bank 1 refers to the side of the engine that has the #1 cylinder. Bank 2 is the opposite side of the engine. If you’ve got a four-cylinder, there will only be one bank, and you would not get this code. A typical heated oxygen sensor

Symptoms

Likely causes

How to fix it

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This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.