Error Code P047C is defined as Exhaust Pressure Sensor B Low Input.

Error Code P047C is a generic trouble code applicable to all equipped vehicles with an engine equipped with variable nozzle turbochargers (both gas and diesel). This includes vehicles made since 2005 such as Ford trucks using 6.0L diesel engines and all Ford with EcoBoost engines, eventually leading to Cummins 6.7L in 2007 and Mercedes lineup in 2007 with 3.0L engine, Cummins 3.0L 6 cylinder in Nissan pickups since 2015. It also applies to some models of Volkswagen and other makes.

Definition

This code is exclusively concerned with the incoming signal from the exhaust pressure sensor not being able to match the intake manifold pressure or ambient pressure key.

Error Code P047B may also be present alongside with the P047C. The difference between the two codes being is that the P047C is caused by an electrical problem, while P0471 can be caused by a mechanical or electrical fault. Experts usually recommended starting with the diagnosis of the P047C (electrical) first before moving on to the P047B (electrical/mechanical) next. This is to determine whether the problem is electrical, as there is a higher percentage of successful repair by starting with the electrical.

Other related codes include:

  • Error Code P047A Exhaust Pressure Sensor “B” Circuit
  • Error Code P047B Exhaust Pressure Sensor “B” Circuit Range/Performance
  • Error Code P047D Exhaust Pressure Sensor “B” Circuit High
  • Error Code P047E Exhaust Pressure Sensor “B” Circuit Intermittent

Common Symptoms

Like most codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms would include:

  • Lack of engine power
  • Vehicle unable to perform manual regeneration – and burn off the soot from the particulate filter (this component looks similar to the catalytic converter, but with a temperature sensor and pressure sensor inserted into it).
  • If vehicle is unable to perform manual regeneration, problem can lead to crank-no start

Possible Causes

Typically, this code is caused by:

  • Circuit between the exhaust pressure sensor and PCM has open signal
  • Circuit between the exhaust pressure sensor and PCM is open in the power supply
  • Short to ground in signal circuit to the exhaust pressure sensor
  • Defective exhaust pressure sensor – internally short to ground
  • Defective PCM (rare)

How to Check

Diagnosis and repair for this code may vary depending on the manufacturer if it’s gas or diesel engine, the type or exhaust pressure sensor, and the color of the wires. Thus, it’s crucial to refer to the vehicle’s specific repair guide to determine which one is the “B” sensor for the vehicle.

The best way to diagnose this code is referring to a TSB (Technical Service Bulletin) for the specific vehicle at fault. Most of the time, the vehicle manufacturer may have a PCM flash/reprogram available to address the issue.

Next, look for the exhaust pressure sensor and disconnect the tube that connects it to the exhaust manifold. Try to blow through it and run a small piece of wire to dislodge the carbon trapped inside that is causing the fault code.

If the tube is free of carbon buildup, then check the connectors and wirings and look for signs of damages, such as chaffing, rubbing, burnt, or bare wires, spots, or plastics.

Pull the connectors apart and then check the terminals (especially the metal parts) inside the connectors. If terminals are corroded, burnt, or possibly green than its normal metal color, then that means a problem. Get an Electrical Contact cleaner to clean the suspect terminals. You can also use 91% rubbing alcohol and a plastic bristle brush to clean.  Let it dry and then use dielectric silicon compound (same used for light bulb sockets and spark plug wires) to the terminals that come in contact. Make sure the tube connects to the turbochargers of the intake manifold, and there is no leaking. Also, check the connection around the turbocharger and intake manifold. Tighten band clamps and all hoses.

Use a scan tool to clear the codes from the memory and see if the code returns. If it does return, that means the problem is in the connection. If it does NOT return, then you will have to test the sensor and its related circuits. Usually, there are 3 wires at the Exhaust Pressure sensor.

Then disconnect the harness that goes to the Exhaust Pressure sensor and then use the DVOM (digital volt-ohm meter) to test for 5V power supply circuit going to the sensor to ensure it’s being powered up. (Read lead to 5V power supply circuit, black lead to good ground). If there is 12V to the sensor when there should be only 5V, then that means an issue in the wiring. Check and repair the wiring from the PCM to the sensor for 12V short. This could also mean a failed PCM.

How to Fix

Common repairs for this error code include:

  • Cleaning of the connectors and terminals of related components
  • Repair or replacement of damaged, burnt, chaffing, or bare connectors or wirings in the Exhaust Pressure sensor
  • Repair or replacement of Exhaust Pressure Sensor

If after doing all these tests and you continue to get the error code, this would mean you have a failed Exhaust Pressure sensor, which means it must be replaced. Although, a failed PCM can also cause this code, which means it’s important to check both.