P1028 – Intake Manifold Air Control Solenoid Short Open Circuit (Audi / VW)

By Bojan Popic (Contact Me)
Last Updated 2023-09-15
Master Mechanical Engineer
CodeFault LocationProbable Cause
P1028 P1028 – Intake Manifold Air Control Solenoid Short Open Circuit (Audi / VW)
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Manufacturer Specific Definitions for P1028

MakeFault Location
AudiIntake manifold air control solenoid - open circuit
BmwPre-Catalyst Fuel Trim Too Rich Bank 1
DodgeIgnition coil, 6 -secondary circuit open
FreightlinerIgnition coil, 6 -secondary circuit open
SaabVariable valve lift oil control valve, LH bank – performance problem
VolvoThrottle Body Internal Fault
VolkswagenIntake manifold air control solenoid - open circuit

Table of Contents

  1. What Does Code P1028 Mean?
  2. Where is the P1028 sensor located?
  3. What are the common causes of code P1028?
  4. Get Help with P1028

What Does Code P1028 Mean?

OBD II fault code P1028 is a manufacturer-specific code, defined by Volkswagen and Audi – which share most of their engine and drivetrain components – as the Intake Manifold Air Control Solenoid Short Open Circuit. This code is set when the vehicle’s PCM detects a described electrical issue with the solenoid that controls the flaps inside the engine’s intake.

To fully understand the meaning of the P1028 code and the effect it may have on the engine’s performance, we must explain how the aforementioned system works.

The intake manifold air control system – more commonly referred to as intake flaps or swirl flaps – is just what their name may suggest – a series of flaps on the engine’s intake ports that open and close depending on the driving conditions. More specifically, when coasting on light throttle, these flaps are partially shut. By doing so, they create an obstacle that upsets the otherwise smooth stream of incoming air before it enters the engine, which, in effect, helps it mix with fuel more efficiently. However, on idle or when the throttle is fully pressed, the flaps are fully open so that they don’t obstruct the airflow.

In Audi and Volkswagen cars that may have the P1028 trouble code, the flaps are opened and closed by a vacuum actuator, whose operation is controlled by an electronic solenoid. The working principle is very similar, if not identical, to that of a vacuum-operated EGR valve and similar devices.

Be aware other carmakers also may use this code, with different definitions between different makes. This guide applies primarily to Audi and Volkswagen vehicles.

Where is the P1028 sensor located?

On VW/Audi gasoline FSI engines that use this system, the intake manifold air control actuator is fitted on the intake manifold’s side, just near the cylinder head. This actuator is then connected to the vacuum solenoid near it, usually bolted at the intake manifold. 

The easiest way to spot all this is to look for an actuator, which is characteristic in shape, as shown in the photo below. Then, follow the rubber hose that attaches to its top side, as this connects to the Intake Manifold Air Control Solenoid. 

What are the common causes of code P1028?

Faulty vacuum solenoid 

The Intake Manifold Air Control Solenoid is a simple device that opens to let the vacuum flow once it receives a signal from the PCM. Like similar vacuum solenoids, it can develop an internal electrical short, which is its most common failure point. 

Damaged wiring 

But before hastily replacing the solenoid, it should be checked, which can be done by measuring the resistance on the solenoid’s pins. Infinite resistance indicates an open circuit, while near-zero values are usually a sign of a short circuit.  

Unplugged connector 

Apart from the faulty solenoid, the issue can also be caused by damaged wiring or a loose connector. Moreover, the whole intake flap mechanism is often overlooked and forgotten about, as these are not overly common on gasoline engines. As a consequence, it’s not rare for it to be left unplugged or not assembled properly during some previous repairs.

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