Nissan P155b-00

Several underlying issues can trigger this DTC. In our experience repairing Nissans, here are the most common culprits:

| Cause | Likelihood | Description | |-------|------------|-------------| | Faulty Coolant Bypass Valve | High | The internal mechanism seizes, or the electric motor fails. This is the #1 cause. | | Wiring or Connector Issues | Medium | Corroded pins, broken wires, or loose connectors at the valve harness. | | Low Coolant Level | Medium | Air pockets in the system prevent proper valve actuation or confuse the temperature sensor. | | ECM Software Glitch | Low | On rare occasions, a software update from Nissan resolves false P155B-00 codes. | | Blown Fuse | Low | The bypass valve circuit may share a fuse with other components. |

The P155B-00 code is a manufacturer-specific diagnostic trouble code (DTC) for Nissan vehicles. In plain English, this code translates to:

"Engine Coolant Bypass Valve 'A' Control Stuck Closed."

The '-00' suffix typically indicates that there is no additional sub-code or specific circuit fault—it is a general logic failure, meaning the engine control module (ECM) has detected that the bypass valve is not operating as commanded. nissan p155b-00

Q: Will P155B-00 clear itself? A: Unlikely. Even if the valve temporarily frees itself, the code will remain in the ECM until cleared with a scan tool. The condition usually recurs quickly.

Q: Can a bad thermostat cause P155B-00? A: No. The code specifically targets the bypass valve, not the main thermostat. However, replacing both components together is often good preventative maintenance.

Q: Does P155B-00 affect emissions testing? A: Yes. In most states, a check engine light with an active DTC is an automatic fail on the OBD-II emissions test.

Q: My Nissan has P155B-00 but runs fine. Do I still need to fix it? A: Yes. The valve can fail fully closed at any moment, leading to sudden overheating. It is not a benign code. Several underlying issues can trigger this DTC

If you are a DIY mechanic or a professional technician, follow this systematic approach:

Based on the diagnostic trouble code (DTC) format, P155B-00 is a manufacturer-specific code used by Nissan and Infiniti vehicles.

Here is a detailed breakdown of the code, its meaning, causes, and diagnosis.

If you own a modern Nissan vehicle—especially models like the Rogue, Altima, Sentra, or Pathfinder—and your check engine light has just illuminated, you might be staring at a code that reads P155B-00 after a scan. Unlike common oxygen sensor or misfire codes, this one often leaves drivers and even some novice mechanics scratching their heads. | | Wiring or Connector Issues | Medium

So, what exactly is Nissan P155B-00? Is it serious? Can you still drive your car? And most importantly, how much will it cost to fix?

In this complete guide, we will break down every aspect of the P155B-00 code, from its technical definition to step-by-step diagnostic and repair procedures.

P155B-00 – Electric Intake Valve Control Actuator Circuit Range/Performance (Bank 1)

This code indicates that the Engine Control Module (ECM) has detected a performance issue or an out-of-range condition in the electric intake valve control actuator circuit for Bank 1. Unlike traditional oil-pressure-driven VVT, some Nissan models use an electric motor-driven actuator for continuous valve lift/timing control (e.g., on MR20DD, QR25DE, or VQ series with electric VVT).

Nissan has acknowledged cooling system valve issues on several models. For example, NTB12-055 and NTB16-085 cover certain Rogue, Altima, and Sentra models with P155B-00-related symptoms. These TSBs often prescribe a software update and/or valve replacement.

Check with a Nissan dealer using your VIN to see if your vehicle qualifies for a warranty extension or free repair—especially if you are under 80,000 miles.