P1387

What it means

On Volkswagen, P1387 refers to the altitude (barometric pressure) sensor built into the engine control unit. The control unit compares the internal sensor reading with other pressure data, such as manifold pressure at key-on or engine off, and has seen a value that is implausible or out of range. It uses altitude data to correct fuelling, boost and ignition, so a bad reading can affect performance.

Symptoms

• Engine warning light on
• Reduced power or the engine going into limp mode
• Poor or uneven running at altitude or under load
• Boost pressure lower or higher than expected on turbo engines
• Fault stored with no other obvious symptoms

Possible causes

• Internal fault in the engine control unit's altitude sensorlikely
• Poor connections or corrosion at the control unit connector causing a bad reference or supply voltagepossible
• Water ingress or damage to the control unitpossible
• Low or unstable battery or supply voltage causing a false readingpossible
• Faulty manifold pressure or boost pressure sensor that the control unit uses for comparisonpossible
• Outdated control unit software where a known calibration fault exists for the model and enginerare

How to diagnose

1. Read all stored codes and freeze frame data, then note whether other pressure sensor or supply voltage faults are present
2. Clear the code and see whether it returns straight away or only under certain conditions
3. Check battery condition and charging voltage, and inspect the battery terminals and earth connections
4. Inspect the control unit connector and wiring for corrosion, moisture, bent pins and damage
5. Compare live barometric pressure with manifold pressure at key-on engine-off and check they agree with the actual local pressure
6. Check the manifold or boost pressure sensor readings, wiring and vacuum or hose connections for plausibility
7. Check with the manufacturer's service information whether a software update or known fault exists for this model and engine

How to fix

• Repair or clean corroded or damaged connectors and wiring at the control unit
• Restore a healthy battery and charging system, and repair poor earth connections
• Replace or repair the control unit if its internal sensor is confirmed faulty, then have it coded and adapted as required
• Replace a faulty manifold or boost pressure sensor if it is the cause of the mismatch
• Fix any water leak that has affected the control unit and dry or replace the affected parts
• Update the control unit software if a known fault is addressed by a newer calibration

Can I keep driving?

This code for other makes

• P1387AcuraCYP Sensor B No Signal
• P1387HondaCYP Sensor B No Signal
• P1387InfinitiCYP Sensor B No Signal
• P1387MazdaCamshaft Position Timing Solenoid 2 Circuit
• P1387OtherVariable Cam Timing Solenoid #2 Circuit Malfunction

Nearby codes

• P1386VolkswagenInternal Control Module Knock Control Error
• P1388VolkswagenControl Unit Internal Throttle Control