Damaged or shorted barometric pressure sensor (often part of the mass airflow sensor); Chafed or pinched wiring harness shorting to battery positive; Corroded or loose connector at the sensor or ECM; Failed ECM internal short on the sensor signal circuit; Aftermarket accessory wiring tapped into the sensor circuit; Water intrusion into the sensor or connector causing a short

DTC codes / Volkswagen codes / P1551

P1551 · VolkswagenBarometric Pressure Sensor Circuit Short To B+

Q: What does code P1551 mean?

Barometric Pressure Sensor Circuit Short To B+. P1551 on Volkswagen vehicles means the engine control module (ECM) has detected a short to battery voltage on the barometric pressure sensor circuit, which is often integrated into the mass airflow sensor or a dedicated sensor. The ECM expects a voltage between roughly 0.5 and 4.5 volts but sees a constant high signal, so it flags the circuit as faulty.

P1551 on Volkswagen vehicles means the engine control module (ECM) has detected a short to battery voltage on the barometric pressure sensor circuit, which is often integrated into the mass airflow sensor or a dedicated sensor. The ECM expects a voltage between roughly 0.5 and 4.5 volts but sees a constant high signal, so it flags the circuit as faulty.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or poor throttle response if the sensor signal is stuck high
Reduced fuel economy due to incorrect altitude compensation
Hesitation or stumble during acceleration
In rare cases, a no-start condition if the ECM misreads barometric pressure

Common causes, most likely first

Damaged or shorted barometric pressure sensor (often part of the mass airflow sensor)
Chafed or pinched wiring harness shorting to battery positive
Corroded or loose connector at the sensor or ECM
Failed ECM internal short on the sensor signal circuit
Aftermarket accessory wiring tapped into the sensor circuit
Water intrusion into the sensor or connector causing a short

How to diagnose and fix it

Scan all modules and record freeze-frame data to confirm P1551 is the only barometric pressure code
Visually inspect the sensor connector and wiring for chafing, corrosion, or signs of shorting to battery positive
Disconnect the sensor and check for battery voltage on the signal wire with the key on; if present, repair the short to B+
Measure resistance of the sensor signal wire to battery positive to locate the short
If wiring is intact, test the barometric pressure sensor with a known-good unit or scan tool live data
Check for aftermarket wiring or accessories that may be backfeeding the circuit
Clear codes and verify the repair with a road test and live data comparison

Barometric sensor shorts you might overlook

On many Volkswagen engines, the barometric pressure sensor is integrated into the mass airflow sensor (MAF), so a failed MAF can set P1551 even when the MAF code is not present.
A short to battery positive can be intermittent and only appear when the engine bay is hot or after hitting a bump, so wiggle-testing the harness while watching live data is essential.
The ECM may substitute a default barometric pressure value, allowing the engine to run almost normally, which is why many drivers notice no symptoms beyond the light.
Aftermarket alarm or remote start wiring tapped into the sensor reference circuit is a common hidden cause of a short to B+ on older Volkswagen models.
Do not replace the ECM until you have verified the signal wire is not shorted to battery positive with the sensor disconnected; a misdiagnosed ECM replacement is expensive and unnecessary.

Can I keep driving with P1551?

You can usually continue driving if the only symptom is the warning light, but avoid hard acceleration and long trips until the fault is repaired because the ECM may be using a default barometric pressure value that affects fuel mixture. If the engine runs rough or stalls, stop driving and have the vehicle 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.