P046C – Exhaust Gas Recirculation Sensor “A” Circuit Range/Performance

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By Reinier (Contact Me)
Last Updated 2023-06-26
Automobile Repair Shop Owner
CodeFault LocationProbable Cause
P046C Exhaust Gas Recirculation Sensor "A" Circuit Range/Performance
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Table of Contents

  1. What Does Code P046C Mean?
  2. Where is the P046C sensor located?
  3. What are the common causes of code P046C?
  4. What are the symptoms of code P046C?
  5. Get Help with P046C

What Does Code P046C Mean?

OBD II fault code P046C is a generic trouble code that is defined as, P046C –“Exhaust Gas Recirculation Sensor “A” Circuit Range/Performance” or sometimes as P046C – “Exhaust Gas Recirculation (EGR) Position Sensor Performance”, and is set when the PCM (Powertrain Control Module) detects an implausible or unexpected input from the exhaust gas recirculation valve’s position sensor.

The purpose of exhaust gas recirculation systems is to divert some exhaust gas from the exhaust systems and then to inject small metered amounts of exhaust gas into the cylinders to quench or reduce the combustion temperature to below the point where oxygen and nitrogen combine.

At or above combustion temperatures of 2200 deg F, oxygen and nitrogen combine to form NOx, a toxic and extremely harmful substance that is implicated not only in the formation of urban smog and acid rain but also in several serious human health issues. These include but are not limited to, potentially life-threatening respiratory problems, several pollution-induced cancers; several types of heart diseases, sudden heart attacks, and strokes in susceptible individuals.

So in a fully functional exhaust gas recirculation system, the PCM will command the exhaust gas recirculation valve to open under some operating conditions to introduce some exhaust gas into the engine, and as a general rule, the introduced exhaust gas will prevent the formation of NOx. However, since the PCM cannot monitor or measure the volume of exhaust gas that passes into the engine through the valve directly, it uses the position of the valve pintle as a guide to infer the volume of exhaust gas that passes through the valve.

As a practical matter, the position sensor monitors the position of the valve pintle in a range of possible movements from fully closed, to fully open. If we assume that both the exhaust gas recirculation valve and its integrated position sensor work as both designed and expected and the valve is 50 percent open, the signal voltage from the position sensor will indicate to the PCM that the valve is indeed 50 percent open.

However, given the corrosive nature of exhaust gas, and the fact that exhaust gas contains high concentrations of unburned fuel and oil residues, it is not surprising that most exhaust gas recirculation valves experience a build-up of carbon and soot deposits. In severe cases, such accumulations of carbon can block a valve completely, but in most cases, lighter carbon deposits can impede or hinder the free movement of the valve pintle.

For example, carbon deposits could prevent an exhaust valve recirculation valve from either opening or closing completely, or from moving at all. This means that if the PCM commands the valve open by any amount, the PCM will expect to see a signal voltage from the valve’s position sensor that corresponds to the commanded opening. Thus, if the input from the position sensor deviates from the input the PCM expects to see by a specified amount, the PCM will interpret the input it receives as implausible/unexpected.

If the above scenario happens, the PCM will recognize that it cannot control the exhaust gas recirculation system effectively, and it will set code P0232 as a result. Note that since a failure of this kind has the potential to increase harmful exhaust emissions, the PCM will also illuminate a warning light that may or may not flash, depending on the vehicle’s make and model.

Where is the P046C sensor located?

This image shows the exhaust recirculation valve’s position sensor on a 2004 Ford Mustang. The shiny metal bar protruding from the sensor is the push rod that is in contact with the valve pintle. As the valve pintle opens, it acts on the push rod, which then exerts pressure on a resistive element that generates a signal voltage the PCM uses to infer the volume of exhaust gas flowing through the valve.

It should be noted that while many EGR valve position sensors can be detached from the main valve, the example of an EGR position shown here is not representative of all EGR position sensors. As s practical matter, the appearance, design, and method of attachment of EGR position sensors vary greatly between different vehicle makes and models. In some cases, the position sensor is incorporated into the EGR valve and it can therefore not be replaced separately.

Based on the above, we strongly recommend that you seek professional assistance with diagnosing and replacing EGR valves/position sensors since many f the symptoms of failed or malfunctioning EGR valves and/or position sensors can also be caused by issues that do not involve any EGR components.

What are the common causes of code P046C?

Common causes of code P046C are largely similar across all applications and could include one or more of the following-

  • Excessive buildup of carbon deposits in the EGR valve that prevents the free movement of the valve pintle
  • EGR valve stuck or frozen in any position between fully open and fully closed
  • Damaged, burnt, shorted, or corroded wiring and/or electrical connectors anywhere in the EGR valve position sensor’s wiring
  • Failed or defective EGR valve position sensor
  • Failed or malfunctioning EGR valve actuators such as vacuum actuators and stepper motors
  • Clogged or severely restricted exhaust gas flow channels or pipes; this is common in applications where exhaust gas is introduced directly into the cylinders via small-diameter channels in the cylinder head(s)
  • Failed or failing PCM but note that since this is an exceedingly rare event, the fault must be sought elsewhere before any control module is reprogrammed or replaced

What are the symptoms of code P046C?

Common symptoms of code P046C could include one or more of the following, but be aware that the severity of symptoms could vary between different vehicle makes and models-

  • Stored trouble code and an illuminated warning light
  • Depending on the nature of the problem, one or more additional codes may be present along with P046C
  • In some cases, there may be no noticeable drivability issues present
  • Varying degrees of power loss may be present
  • Fuel consumption may increase noticeably
  • The vehicle may emit large volumes of smoke from the tailpipe under some operating conditions
  • The engine may stall unexpectedly or repeatedly at low engine speeds
  • The engine may overheat severely under some operating conditions
  • Severe engine knocking may be present under high engine load conditions
  • In some cases, it may be difficult to start the engine when it is hot
  • The engine may stumble or hesitate upon acceleration
  • The vehicle may surge or hesitate by turns at some or all engine speeds and loads
  • One or more readiness monitors may not initiate or run to completion
  • The vehicle will not pass a mandatory emissions test

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