On an applicable AVLS-equipped Forester, P0028 means Bank 2 intake valve-control feedback did not match the commanded lift state. Confirm the EJ engine and system first: later FB25 and FA20 engines use different valve-control strategies. Verify oil level, grade, filter and pressure, save AVLS switch and command data, load-test the Bank 2 pressure switch, switching solenoid and wiring, then compare banks. P0028 AVLS valve lift is not the same fault as P0021 AVCS cam timing.
Match the symptom
Select the closest observation. The result changes the first test; it does not name a part to replace.
Save oil temperature, load and switching-command data.
What can set P0028—and how to separate it
The order below is evidence-driven, not a universal probability ranking. Vehicle year, repair history, companion codes and the operating condition in freeze frame change where diagnosis should begin.
| Possible cause | Evidence that supports it | First useful test |
|---|---|---|
| Bank 2 AVLS oil-pressure switch or circuit | Switch state is implausible during command | Switch and loaded-circuit test |
| AVLS switching solenoid or connector fault | Command/current or coil test fails | Solenoid actuation test |
| Low, wrong or contaminated engine oil | Level/specification or service history is abnormal | Oil and filter audit |
| Restricted oil passage or inadequate pressure | Electrical tests pass but switching pressure does not | Mechanical pressure test |
| Mechanical valve-lift/rocker fault | Correct hydraulic command with persistent bank contribution problem | Valvetrain inspection |
Do not search for AVLS hardware on the wrong engine
Decode the VIN and confirm the engine code before locating the pressure switch and solenoid. Forester model names span engines that do not share the same lift system.
Generic P0028 descriptions may resemble a VVT solenoid code. On the applicable Subaru system, the diagnostic relationship is ECM command, switching oil pressure and valve-lift feedback.
Test the circuit while it carries load
Inspect oil contamination, terminal grip and harness routing, then test solenoid current and pressure-switch state. A cold resistance check may miss an intermittent hot connector.
Verify the specified oil and mechanical pressure before condemning electronics. Restricted oil galleries or unsuitable viscosity can prevent hydraulic switching even when the command circuit works.
Compare banks before opening the valvetrain
Record both bank switch states at equal temperature and rpm. If Bank 1 changes correctly and Bank 2 does not, the comparison narrows electrical, hydraulic and mechanical possibilities.
Only inspect rocker/lift hardware after circuit and pressure evidence support it. Confirm correct state transition and no pending P0028 under the original enable conditions.
Save these scan-data clues
Freeze frame is a snapshot of conditions when the PCM matured the fault. It can distinguish an idle-only problem from a load, cold-start or monitor-completion problem. Clearing first throws that context away.
- Exact VIN, platform, model year and engine sales code
- All confirmed, pending and permanent companion codes
- RPM, load, coolant temperature and vehicle speed
- Relevant commanded and actual scan data
- Recent service, repairs and symptom conditions
- Manufacturer bulletin and current software/VIN status
A practical diagnostic workflow
- 01Confirm engine and code definition
P0028 applies to the AVLS-equipped configuration, not every Subaru engine.
- 02Save command and switch data
Record rpm, temperature and load before clearing.
- 03Verify oil and pressure
Use the exact viscosity, filter and engine specification.
- 04Test Bank 2 switch and solenoid circuits
Use loaded tests, not continuity alone.
- 05Command AVLS and compare banks
Separate electrical, hydraulic and mechanical failure.
- 06Inspect passages and valvetrain only as evidence directs
Avoid replacing cam-timing parts for an AVLS code.
- 07Verify at the original enable condition
Confirm correct switching and no pending P0028.
Do not replace the most commonly named component from P0028 alone. Confirm the exact engine, preserve evidence and complete the manufacturer test sequence before ordering parts.
Why the model year changes the test
Forester diagnostics span SF through SK generations with EJ-series SOHC and turbo engines, FB25 and FA20 direct-injection turbo applications. AVLS and AVCS are different systems, bank orientation matters, and catalyst, EVAP and oxygen-sensor hardware changes by year and engine. Confirm VIN, model year, engine code, turbo status, emissions label and current ECM calibration before using any test or bulletin.
- Applicable older EJ25 SOHC AVLS Foresters use oil-controlled valve-lift switching.
- Later FB and turbo FA engines require their own code definition and hardware map.
- Bank 2 is the applicable left-hand boxer bank; confirm service-manual orientation.
- Valvetrain noise or an oil-pressure warning requires stopping.
P0028 FAQ
Is P0028 a cam-timing code on these Subarus?+
On applicable AVLS-equipped engines it concerns Bank 2 intake valve-control range/performance, not the same system as P0021 AVCS timing.
Can low oil cause it?+
Yes. AVLS switching depends on controlled oil pressure.
Can I drive?+
Limit driving and stop for pressure warnings, noise or severe running problems.
Is Bank 2 the left cylinder bank?+
Subaru service information identifies Bank 2 as the left-hand bank on the applicable boxer engine; confirm the VIN-correct manual and viewing convention.
Should I replace the solenoid first?+
No. The pressure switch, wiring, oil supply and mechanical lift system need testing.
Can the wrong viscosity matter?+
Yes, particularly when the fault is temperature or rpm dependent.
Does P0021 use the same diagnosis?+
No. P0021 is an intake cam-timing performance code on AVCS-equipped applications.
What confirms repair?+
Correct Bank 2 switching data at the original enable condition with no pending P0028.
Ford diagnostic references
These documents explain Ford monitor operation. Exact pinpoint tests, connector views and specifications must be selected for the truck's VIN and model year in current service information.
01Subaru Technical Information System (STIS)Current VIN-, engine- and model-year-specific service-manual diagnostic procedures↗02Subaru owner manuals and vehicle resourcesOfficial model-year operating, warning, fuel and maintenance information↗