What is the code P0237 Turbo Boost pressure sensor circuit low?
The turbo boost pressure sensor circuit A is reporting a voltage that is too low, indicating under-boost or a fault in the sensor circuit.
The code is triggered when the engine control unit detects the Boost Sensor A signal is below the expected range, which can be caused by a defective sensor, wiring problems, vacuum/boost leaks, a faulty boost control solenoid, or turbocharger issues. Here is a detailed look at what P0237 means, its common causes, symptoms, and how to diagnose and fix it.
What P0237 Means
P0237 is one of several codes related to turbo boost pressure. It specifically points to the Boost Sensor A circuit, which monitors the pressure feeding into the turbocharger or the intake manifold. When the signal is abnormally low, the ECU may not be able to properly regulate boost, potentially causing under-boost conditions, reduced power, and increased fuel consumption.
How Boost Sensors Work
In turbocharged engines, the boost sensor (MAP sensor) provides the ECU with real-time pressure data. It helps regulate fuel and ignition timing as boost rises. There are often multiple sensors (A and B) to monitor different stages of the system or different banks. A low reading on sensor A means the ECU perceives less pressure than expected, even when boost is demanded.
Common Causes
These are the issues most frequently associated with P0237. The list includes both electrical and mechanical problems that can trigger a low-signal condition.
- Faulty MAP/Boost pressure sensor A
- Damaged or corroded wiring harness or connectors to the sensor
- Bad ground or power supply to the sensor circuit
- Vacuum leaks or boost leaks in intake piping, intercooler hoses, or PCV system
- Faulty turbocharger variable geometry or boost control solenoid stuck or failing
- Intermittent sensor signal due to wiring movement or poor connector seating
- ECU/PCM software calibration or fault
- Restrictions in the intake or exhaust that limit boost development (e.g., exhaust leak, clogged catalytic converter, collapsed hose)
Addressing the root cause is essential, as a stuck boost solenoid or leaks can allow the engine to operate in limp mode or misfire, risking damage.
Symptoms You Might Notice
Several signs might accompany P0237. The following list details typical vehicle responses and performance changes.
- Reduced engine power under acceleration or when requesting boost
- Poor or inconsistent fuel economy
- Check Engine Light (CEL) with P0237 stored
- Turbo spiking or whistling sounds if there are leaks
- Limp mode activation on some vehicles
- May feel normal at idle and under light load if the issue is intermittent
Note that symptoms can vary by vehicle, trim, and whether the fault is intermittent or persistent.
How to Diagnose and Fix
Diagnosing P0237 involves both visual inspection and electrical testing, plus pressure testing in severe cases. Use a hands-on approach and rely on scan data to identify whether the sensor or its circuit is to blame, or if a boost leak or mechanical issue is the root cause.
- Scan the vehicle with an OBD-II scanner to confirm P0237 and review freeze-frame data for rpm, load, MAP sensor voltage, and boost readings.
- Inspect the MAP Boost Sensor A connector and wiring for corrosion, damage, or loose connections. Check for continuity and resistance against the manufacturer's specs.
- Test the MAP sensor: supply 5V reference, ground, and read the signal with a multimeter or oscilloscope. Compare readings to expected range at idle and with vacuum/boost applied.
- Check vacuum/boost lines for leaks or cracks. Inspect hoses between the turbo, intercooler, throttle body, and intake manifold; replace damaged lines if found.
- Inspect the boost control system, including the wastegate actuator or variable geometry mechanism and the boost control solenoid, to ensure proper operation.
- Perform a boost leak test and, if practical, test the system on a known-good vehicle or with a diagnostic vacuum pump to isolate leaks.
- If the sensor reads correctly and wiring is solid, consider replacing the MAP sensor itself. If the code persists after sensor replacement, re-check wiring and possible ECU concerns.
- Clear codes and re-test to confirm that P0237 does not return. If it does, escalate to a professional mechanic with engine-aeration test equipment.
Good practice includes addressing the issue promptly to avoid potential engine damage and to restore optimal performance.
Vehicle-Specific Notes
While the general cause and fix apply to most turbocharged engines, some makes have unique wiring or sensor configurations (for example, Ford, VW/Audi, GM, and Dodge). Always refer to the service manual for your specific vehicle and adapt testing steps to the exact MAP sensor voltage range and harness layout.
Summary
P0237 signals a low input on Boost Sensor A circuit, suggesting under-boost or a fault in the sensor circuit. Causes range from a faulty MAP sensor, damaged wiring, poor grounds, vacuum or boost leaks, to boost control or turbo issues. Diagnosis relies on scanning data, visual inspection, electrical testing, and pressure/leak testing. Repairs typically involve replacing the MAP sensor or repairing wiring and leaks, followed by clearing codes and confirming repair.
