Failed turbocharger bypass valve (diverter valve) with an internally shorted solenoid.; Chafed or pinched wiring harness between the valve and the engine control module, shorting to a battery positive wire.; Corroded or water-contaminated connector at the bypass valve, allowing voltage to bleed across pins.; Faulty engine control module driver for the bypass valve circuit, though this is rare.; Aftermarket or incorrectly installed electrical accessories tapping into the same circuit.; A short to battery voltage inside the valve's internal electronics from heat or oil intrusion.

DTC codes / Volkswagen codes / P1288

P1288 · VolkswagenTurbocharge Bypass Valve Short To B+

Q: What does code P1288 mean?

Turbocharge Bypass Valve Short To B+. P1288 on Volkswagen vehicles means the engine control module has detected a short to battery voltage on the control circuit for the turbocharger bypass valve, also called the diverter valve. The computer commands the valve to open or close, but the circuit voltage stays high even when the valve should be off, indicating a wiring or valve fault rather than a boost pressure problem.

P1288 on Volkswagen vehicles means the engine control module has detected a short to battery voltage on the control circuit for the turbocharger bypass valve, also called the diverter valve. The computer commands the valve to open or close, but the circuit voltage stays high even when the valve should be off, indicating a wiring or valve fault rather than a boost pressure problem.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms.
Reduced engine power or limp mode during hard acceleration.
Poor throttle response and sluggish turbo spool-up.
Rough idle or stalling after lifting off the throttle.
A faint clicking or buzzing noise from the diverter valve area when the ignition is on.

Common causes, most likely first

Failed turbocharger bypass valve (diverter valve) with an internally shorted solenoid.
Chafed or pinched wiring harness between the valve and the engine control module, shorting to a battery positive wire.
Corroded or water-contaminated connector at the bypass valve, allowing voltage to bleed across pins.
Faulty engine control module driver for the bypass valve circuit, though this is rare.
Aftermarket or incorrectly installed electrical accessories tapping into the same circuit.
A short to battery voltage inside the valve's internal electronics from heat or oil intrusion.

How to diagnose and fix it

Scan all modules and record freeze-frame data for P1288 to confirm the fault is active and not a historical ghost code.
Visually inspect the bypass valve connector and the harness routing for chafing, corrosion, or oil contamination.
Disconnect the valve and measure voltage on the control wire with the key on; a constant battery voltage indicates a short to B+ in the harness.
Check the valve's internal resistance and compare it to the manufacturer's specification to rule out a shorted solenoid.
Wiggle-test the harness while watching live data for the bypass valve command to catch intermittent shorts.
Repair or replace the damaged section of harness, then clear the code and verify the circuit behaves correctly during a road test.
If the harness and valve test good, substitute a known-good valve and recheck before condemning the engine control module.

What a short to B+ really means here

A short to B+ does not mean the valve is stuck open or closed; it means the control wire is receiving battery voltage when it should be grounded or floating, so the valve may still move mechanically.
Many technicians replace the diverter valve first, but a chafed harness near the hot turbocharger or a corroded connector is just as common and far cheaper to fix.
This code can set intermittently after a car wash or heavy rain if water enters the valve connector, so always check for moisture before condemning parts.
Volkswagen's diverter valve is pulse-width modulated, so a short to B+ can also cause the valve to buzz or stay energized, leading to overboost codes later if ignored.
A failing battery or charging system that spikes voltage can trigger P1288 without any actual wiring fault, so check system voltage first.

Can I keep driving with P1288?

You can usually drive the car gently to a repair shop, but avoid hard acceleration and sustained boost because the bypass valve may not regulate pressure correctly. If the engine enters limp mode or you hear unusual turbo noises, stop driving and have it towed.

Tools that help

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Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.