|Trouble Code||Fault Location||Probable Cause|
|P2562||Turbocharger (TC) boost control position sensor - circuit malfunction||Wiring, TC boost control position sensor|
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What Does Code P2562 Mean?
OBD II fault code P2562 is a generic trouble code that is defined as “Turbocharger (TC) boost control position sensor – circuit malfunction”, and is set when the PCM (Powertrain Control Module) detects a failure, defect, or malfunction in the electrical circuit that controls/manages/monitors the turbocharger’s boost control system. Note that some sources list this code with the definition “P2562 – Turbocharger Boost Control Position Sensor “A” Circuit”, but despite the slight difference in wording, both trouble code definitions refer specifically to the control circuit of the position sensor in the boost control system.
While turbochargers are hugely effective in boosting the power output of internal combustion engines, and particularly gasoline engines with small displacements, the effects of forced induction are such that the volume of additional air (that is forced into an engine) must be strictly controlled to prevent mechanical damage from occurring to the engine. This is particularly true of modern small-capacity gasoline engines that are, for the most part, made from various aluminum alloys to reduce their overall weight.
In practice, a small, lightweight gasoline engine has to be able to withstand the higher compression ratios and combustion pressures that come with forced induction without flexing or deforming under the increased loads to eliminate excessive mechanical wear and possible stress failures of engine components. However, while modern casting and manufacturing methods produce engine castings that are immensely strong and rigid, there is a limit to how rigid an engine casting can be made without the need to increase its weight/strength by increasing the casting’s thickness.
Thus, as a result of the trade-offs between weight, strength, and manufacturing costs, engine designers need to strike a fine balance between the maximum power that can be extracted from the engine, while reducing fuel consumption and exhaust emissions to the minimum, at the same time. We need not delve into the finer details of these calculations here, beyond saying that the turbocharger and its control system on a stock application are designed so that the maximum boost pressure will not exceed the engine’s ability to withstand the additional mechanical loads and stresses.
However, since turbochargers are driven by the exhaust gas* that exits the engine, the turbocharger’s speed could be increased to the point where the maximum allowable boost pressure could be exceeded. To prevent this, all forced induction systems are fitted with relatively simple mechanical devices that are designed to reduce or limit the turbocharger’s rotational speed by limiting the pressure of the exhaust gas that drives the turbocharger.
* This is also known as the “drive pressure”.
These devices are commonly known as “waste gates” or “dump valves” that are controlled in various ways. Regardless of the control mechanism, though, all waste gates dump some exhaust gas into the exhaust system under some conditions to limit the rotational speed of the turbocharger as a means to limit or reduce boost pressure. As a practical matter, all modern forced induction systems use dedicated boost pressure sensors that relay the actual boost pressure to the PCM, which then uses this data to command an actuator to manipulate the wastegate. In practice, the position sensor is a simple potentiometer that is linked to the wastegate; as the wastegate’s position changes, varying amounts of current pass back to the PCM, which the PCM interprets as degrees of opening [of the waste gate].
In this way, the PCM can open or close the wastegate to control the turbochargers’ rotational speed- if the wastegate is closed, the drive pressure increases, and the boost pressure increases by a predictable amount because the turbocharger speeds up. Conversely, if the wastegate opens, drive pressure decreases, and boost pressure drops by a predictable amount because the turbocharger slows down.
While this arrangement works reasonably well, it does have the disadvantage that it produces large fluctuations in boost pressure, since the wastegate is either fully open or fully closed. Therefore, by adding a position sensor to the wastegate to monitor the position of the wastegate relative to known open and closed positions, the PCM can exercise precise control over the position of the wastegate. Thus, in a fully functional system, the PCM can sense when the boost pressure is approaching the maximum allowable threshold and open the wastegate by a calculated percentage, as opposed to opening it fully to dump all the available drive pressure into the exhaust system.
Similarly, by using pre-programmed look-up tables, the PCM can also sense when the boost pressure is approaching a less than ideal value via input data from the boost control sensor. Based on this data, the PCM can then adjust the position of the wastegate in both directions by small increments to maintain the boost pressure at an ideal level during much of the engine’s operating range. The practical advantages of this are that-
- turbo lag is reduced, if not eliminated at low engine speeds
- over boost conditions are prevented at mid to high engine speeds
- boost pressure is kept closer to ideal values more often than is possible to do without a wastegate position sensor
When a fault, defect, or malfunction occurs that prevents the PCM from determining the actual position of the wastegate, as opposed to its desired position, it will recognize that it cannot control the boost pressure effectively, and it will set code P2562 and illuminate a warning light as a result.
Where is the P2562 sensor located?
This image shows an example of a typical vacuum controlled turbocharger wastegate actuator. In this example, the red circle indicates the integral position sensor; the green arrow indicates the attachment point for the vacuum system that controls the actuator, and the yellow arrow indicates the point where the actuator attaches to the actual turbocharger wastegate.
Note, though, that while most vacuum controlled wastegate actuators are located directly on turbochargers and follow this general pattern, some electrically operated actuators may have a single connector that serves both the actuator’s stepper motor and the incorporated position sensor. If there is any doubt about whether a wastegate is controlled by a vacuum or an electric stepper motor, look for a vacuum attachment point as shown here. If there are no vacuum connections, the actuator is electronically controlled. Be aware, though, that in many cases, the position sensor is incorporated into the actuator. In these cases, the actuator and position sensor must be replaced as an assembly.
What are the common causes of code P2562?
Common causes of code P2562 are largely similar across all applications, and could include one or more of the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors
- Mechanical failure of the wastegate
- Gross leaks in intake ducting
What are the symptoms of code P2562?
Common symptoms of code P2562 are much the same across all applications, but note that depending on both the application and the nature of the problem, the severity of one or more symptoms listed here could vary between applications-
- Stored trouble code and illuminated warning light
- Turbo lag may be excessive
- Varying degrees of power loss may be present
- Fuel consumption may increase
- Over-, or under boost conditions may occur under some operating conditions, but note that these conditions will typically be indicated by dedicated codes in addition to P2562
- Misfires at high engine speeds may occur on some applications as the result of abnormal boost conditions