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P2055 OBD-II Trouble Code: Reductant Injector Circuit High Bank 1 Unit 2

check engine light

P2055 code definition

When the Powertrain Control Module (PCM) detects a variation in the voltage coming from the reductant injector air pressure sensor circuit, a P2055 trouble code is stored. Used most often in diesel engines, the reductant injector air pressure sensor circuit is also found in gasoline and turbocharged engines. A reductant injector system helps cool the exhaust, making it easier for the catalytic converter to reduce the emissions commonly found in the vehicle exhaust. Some other related codes include P2047, P2048, P2049, P2050, P2051, P2052, P2053, P2054, P2056, P2057, and P2058.

What the P2055 code means

A P0255 trouble code means that the reductant injector air pressure sensor has detected a malfunction. This, in turn, causes a code storage on the PCM and the Check Engine Light to come on. Bank 1 is the bank that contains the number one cylinder in the engine, while unit 2 is one of two things – the post diesel particulate filter, also known as the catalytic converter, and the downstream sensor. Keep in mind that multiple drive cycles might be required in some model of vehicles before the Check Engine Light is lit, though a P0255 trouble code is stored upon the initial incident.

What causes the P2055 code?

A P0255 trouble code is most often caused by loose or damaged wiring or connectors. Some other causes include a faulty sensor, a decrease in back pressure, a severe upstream exhaust leak, and the exhaust gas temperature sensor being shorted, either internally or to the ground.

What are the symptoms of the P2055 code?

The only visible sign of a P0255 trouble code is excessive black smoke emanating from the vehicle's tailpipe upon acceleration.

How does a mechanic diagnose the P2055 code?

Diagnosing a P0255 trouble code requires a mechanic to use an infrared thermometer with a laser pointer, a digital volt/ohmmeter, and an OBD-II scanner or code reader. In addition to the proper tools, a mechanic should perform the following steps when diagnosing this code:

  • Inspect all wiring and connectors for looseness and damage. This includes burnt, corroded, or otherwise damaged wiring and connectors.

  • Download any freeze frame data or stored codes by connecting the OBD-II scanner to the diagnostic connector.

  • Visually examine the exhaust gas temperature/pressure sensor and any associated circuitry.

  • Check the resistance of the exhaust gas temperature/pressure sensor using a digital volt/ohmmeter.

  • If the resistance of the exhaust gas temperature/pressure sensor checks out, leave the volt/ohmmeter attached and heat the sensor with a heat gun, observing the resistance level of the sensor as the temperature increases, making sure it decreases smoothly.

  • Use the volt/ohmmeter to check the PCM for continuity.

  • Clear the code and test the system to see if the code returns.

Common mistakes when diagnosing the P2055 code

A common mistake made by a mechanic diagnosing a P0255 trouble code is to mistake the oxygen sensor for the exhaust gas temperature sensor. Also, another misdiagnosis is for the mechanic to mistakenly think the oxygen sensor is somehow integrated into the exhaust gas temperature sensor, so they replace the oxygen sensor. Replacement of the oxygen sensor will not fix the problem in both of these cases, and the a mechanic can expect the code to return.

How serious is the P2055 code?

A fault with the exhaust gas temperature/pressure sensor within the reluctant injection system can lead to higher vehicle emissions.

What repairs can fix the P2055 code?

Repairing a P0255 trouble code can be a multistep process and often requires the mechanic to perform the following:

  • Repair any damaged wiring, connectors, or components.

  • Replace the exhaust gas temperature/pressure sensor if found to be at fault.

  • Replace and reprogram the PCM if faulty.

  • As a last resort, the mechanic can also install an inline resistor, of at least 2.5 ohms between the signal and ground wires of the PCM, and leaving the exhaust gas temperature sensor disconnected.

Additional comments for consideration regarding the P2055 code

Before removing any parts related to a vehicle's emission system, the mechanic should check local, state, and federal laws to make sure they stay within compliance.

Need help with a P2055 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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