On an applicable older Outback with Subaru's Active Valve Lift System, P0028 concerns Bank 2 intake valve-control range/performance. The ECM expects the AVLS oil-pressure switch to agree when the switching solenoid redirects oil to the rocker mechanism. Verify the exact engine actually has AVLS, then check oil level, viscosity, filter and pressure; save switch/command data; load-test the Bank 2 switch, solenoid and harness; and compare operation with Bank 1. Do not use a P0021 AVCS cam-timing repair for this code.
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 |
First prove the vehicle has the system named by the code
Outback generations include EJ, FB, FA and EZ engines with different valve-control hardware. Decode the VIN and read the emissions/service data before searching for a Bank 2 AVLS pressure switch that a later engine may not contain.
Generic scanners sometimes shorten P0028 to a vague solenoid description. Subaru's applicable test evaluates the relationship among ECM command, oil pressure, switching valve and pressure-switch feedback.
Electrical agreement and hydraulic action are separate questions
Load-test power, control, ground and terminal grip at the switching solenoid and pressure switch. A resistance reading through a weak connection does not demonstrate that the circuit carries current when hot.
If the electrical path passes, verify oil pressure and passage flow under the specified enable condition. Wrong viscosity, low level, sludge or a restricted gallery can prevent the switch from changing even when the solenoid clicks.
Mechanical lift comes last, not first
Compare Bank 1 and Bank 2 switching data at the same oil temperature and rpm. Correct command with incorrect pressure feedback narrows the switch, oil supply or mechanical AVLS path.
Inspect rocker and lift hardware only after electrical and hydraulic evidence supports it. Verification is correct Bank 2 state change at the original condition and no pending P0028.
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
Outback diagnostics span Legacy-based early models through modern crossovers with EJ25, EZ30/EZ36, FB25 and FA24 turbo engines. Valve-lift hardware, AVCS strategy, fuel injection, bank layout, rear oxygen sensors, catalysts and EVAP leak detection changed repeatedly. Confirm VIN, model year, engine code, aspiration, emissions label and current ECM calibration before applying a code definition, bank location or bulletin.
- P0028 is relevant to applicable AVLS-equipped EJ25 SOHC configurations, not every Outback engine.
- AVLS changes valve lift; AVCS changes cam phase.
- Bank 2/left-hand orientation must be confirmed with VIN-correct Subaru service information.
- Oil-pressure warnings or valvetrain noise require stopping operation.
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↗