You can generally keep driving with P0035 — the engine still runs and makes boost — but you may hear compressor flutter on lift-off and feel less crisp response. Repair it before long to avoid stressing the turbo and to restore clean throttle behavior. P0035 means the powertrain control module saw a HIGH voltage — an open circuit or a short to power — in the control circuit for turbocharger bypass valve "A". That valve is the boost-relief (recirculation/diverter) valve the PCM opens on throttle lift to vent compressor pressure and stop the turbo from surging, so with the circuit reading high the module can no longer command it electrically.
What P0035 means
On a gasoline turbo engine the compressor keeps spinning and pushing air even when you snap the throttle shut. To bleed that trapped pressure the PCM opens a turbocharger bypass valve — also called the recirculation or diverter valve — which routes the boost back to the compressor inlet so it doesn't stall and "flutter" against the closed throttle. On Ford's 3.5L EcoBoost this is the electronically actuated bypass valve; Ford labels its wiring the TCBY circuit. P0035 is the circuit-HIGH member of the family: the PCM energizes the valve, watches the voltage on its control line, and sets the code when it reads abnormally high — which points to an open circuit (a break, unplugged connector, or failed valve winding) or a short to voltage. Per Ford's own logic the code only sets while the valve is actually commanded open, so it is an active-driver fault rather than a static one. It is the opposite failure mode to P0034 (the same circuit reading LOW / short-to-ground), and it is a distinct valve from the wastegate/boost-control solenoid family (P0045/P0046/P0047) even though both live in the turbocharger control system. With the bypass valve unable to respond, the compressor can surge on lift-off and boost delivery may feel inconsistent.
Symptoms
- Check-engine light on, typically stored with turbocharger/boost-related freeze-frame data
- Audible compressor surge or "flutter" chatter from the turbo when you lift off the throttle
- Hesitation, a brief flat spot, or inconsistent boost when you get back on the throttle after a lift
- Possible mild loss of power or a slightly rougher, less crisp response under boost
- In some cases no obvious drivability change at all — just the stored code — because the fault only registers while the valve is commanded open
Common causes
- Open circuit in the bypass valve control wire (Ford's TCBY circuit) — a break, corroded splice, or backed-out terminal
- Failed turbocharger bypass (recirculation/diverter) valve with an open or high-resistance internal winding
- Disconnected, loose, or corroded valve connector so the PCM sees no return current
- Short to voltage where the control wire chafes against a power feed, pushing the circuit high
- Damaged or melted harness near the hot turbo/exhaust that has opened or shorted the control wire
- Water intrusion or corrosion in the connector creating a high-resistance (open-like) path
- Failed PCM valve driver (uncommon — confirm the wiring, connector, and valve first)
Severity & driving advice
Severity: Moderate — Usually drivable, but the turbo can surge on throttle lift and boost may feel inconsistent; not an immediate hazard, so repair when convenient.
Can I drive? You can generally keep driving with P0035 — the engine still runs and makes boost — but you may hear compressor flutter on lift-off and feel less crisp response. Repair it before long to avoid stressing the turbo and to restore clean throttle behavior.
Diagnostic approach
- Scan codes and read freeze-frame — Confirm P0035 is present and note any companion codes plus the RPM, load, and boost stored when it set. Check for the sibling P0034 (same bypass-valve circuit reading low) or the wastegate/boost-control family (P0045–P0048), since those change the diagnostic path. Remember Ford's chart notes the code only sets while the bypass valve is commanded open.
- Inspect the valve connector and harness — Because P0035 is an open/high fault, examine the turbocharger bypass valve connector and its wiring for a break, backed-out or spread pins, corrosion, or moisture, and follow the run for chafed, pinched, or melted insulation — pay attention to any point near the hot turbo or exhaust where the harness can be damaged. Ford's diagnostic aids specifically call for checking the harness for intermittent faults, wrong connections, poor routing, and contact damage.
- Identify the two circuits — The bypass valve uses a fused power feed on one pin and the PCM control (driver) on the other — the TCBY control circuit. Confirm which wire is the control line and which is the feed before probing so you test the correct side for an open or a short to voltage.
- Test the control wire for continuity and shorts to power — With the valve connector unplugged and the PCM disconnected, check the control wire end-to-end for continuity — an open (infinite resistance) confirms a broken circuit. Then, key on, probe the control wire for unexpected voltage with the PCM still disconnected; battery voltage present there points to a short to voltage. Wiggle-test the harness while measuring to catch an intermittent break that only appears with movement or heat.
- Measure the bypass valve winding — With the connector off, measure resistance across the valve's two terminals. An open or far-above-spec reading indicates a failed valve with a broken or high-resistance winding rather than a wiring problem (verify the exact resistance spec for the vehicle). Also check each terminal to the valve body for an unintended short.
- Verify the power feed and PCM driver — Key-on, confirm the feed pin has voltage (check the fuse first). If the wiring and valve both test good, the concern can be an open or high-reading PCM driver — back-probe the control line to see the commanded signal while the valve is energized, and only condemn the module after the harness, connector, and valve are cleared. Ford routes this to Pinpoint Test HN (Turbocharger System).
- Repair, command the valve, then road-test — After repairing the open or short, replacing the bypass valve, or fixing the connector, use the scan tool's bidirectional test to command the valve and confirm it actuates. Clear P0035, then drive through several throttle lift-and-reapply cycles under boost and watch for the code to stay off and the surge/flutter to disappear.
FAQ
Is it safe to drive with a P0035 code?
In most cases yes, at least for a while. The bypass valve mainly protects the turbo from compressor surge when you lift off the throttle, so the engine still runs and builds boost with the code set. You may hear flutter and feel slightly softer response, and prolonged surging is hard on the turbo, so it is best to get it fixed before long rather than ignoring it.
What is the difference between P0035 and P0034?
Both codes are about the same turbocharger bypass valve "A" control circuit but describe opposite electrical faults. P0035 is circuit HIGH — the PCM reads an abnormally high voltage, meaning an open circuit or a short to voltage. P0034 is circuit LOW — a short to ground or the driver pulled low. The valve, connector, and wire are the same; you just test for an open/short-to-power with P0035 versus a short-to-ground with P0034.
Is the bypass valve the same as the wastegate?
No. The bypass (recirculation/diverter) valve vents trapped compressor pressure back to the turbo inlet when you close the throttle, preventing surge. The wastegate, controlled by the boost-control solenoid (the P0045/P0046/P0047 family), routes exhaust around the turbine to cap how much boost the turbo makes. P0035 is specifically about the bypass valve's control circuit, not the wastegate.
Can a wiring or connector problem alone set P0035?
Yes, and it is one of the most common causes. Because P0035 flags a high/open reading, a broken or corroded control wire, an unplugged or contaminated connector, or a wire chafed against a power feed will set it even when the valve itself is fine. Ford's diagnostic aids stress checking the harness for intermittent faults and contact damage, since the code only sets while the valve is commanded open. Inspect and test the wire and connector before replacing the valve.
Will P0035 cause my turbo to fail?
Not directly — the fault is in the bypass valve's electrical circuit, not the turbo cartridge. However, if the valve can't open to relieve pressure, repeated compressor surge on throttle lift puts extra stress on the turbo over time. Fixing the circuit or valve restores normal boost relief and protects the turbocharger, so it is worth addressing rather than leaving indefinitely.