P0237 - Turbocharger/Supercharger Boost Sensor A Circuit Low

P0237 - Turbocharger/Supercharger Boost Sensor A Circuit Low

Overview

• Definition DTC, i.e., part of the OBD-II Powertrain Codes category. Emissions-related and engine control systems are monitored by the PCM and may illuminate the CEL when a fault is detected.

What This Code Means

• The PCM (engine control module) detects that the Boost Sensor A circuit is reporting a lower-than-expected signal. This could indicate:
  • A sensor reading that is genuinely low (actual boost is low due to a problem).
  • A faulty sensor or degraded wiring/connector causing a low signal.
  • A problem in the sensor supply (5V reference) or ground path, causing an unreliable low signal.
• In short: the boost pressure sensor A circuit is reading or presenting a "low" condition that falls outside the expected range for that sensor input.

What you might notice (symptoms)

• Check Engine Light (CEL) or ABS/ MIL indicator illuminated.
• Noticeable loss of engine power or reduced acceleration, especially under load or during turbo boost.
• Poor throttle response or limp-home mode in some vehicles.
• Degraded fuel economy or unusual engine behavior under boost conditions.
• In some cases, related boost-related or sensor-related fault codes may appear alongside P0237.

Probable Causes

Note: The following probabilities are guidance-based since do not include NHTSA complaint analytics. They reflect typical real-world patterns for this class of code.

• Boost sensor A circuit fault or sensor itself: 40-60%
  • Sensor is out of range, degraded, or has internal fault; may read low in diagnostic data or fail to respond properly.
• Wiring harness or connector issues (pin, insulation, corrosion, short to ground, open circuit): 25-35%
  • Damaged or corroded connector pins, pin backs, or harness damage near the sensor or along the route to the PCM.
• Vacuum/boost leak or turbocharger system issue (intercooler hoses, pipes, clamps, or wastegate actuator): 15-25%
  • A genuine loss of boost or leak can produce a sensor reading that the PCM interprets as "low" signal or may cause the sensor to report low if the system cannot reach commanded boost.
• Boost control/actuator problems (wastegate, boost control valve/solenoid): 5-15%
  • If the system cannot achieve boost, the sensor signal may consistently be at the low end; or the actuator could be misbehaving and not producing expected pressure.
• PCM/ECU fault or calibration issue: 5-10%
  • Less common, but possible in certain vehicles or after software updates.

Diagnostic Approach

1) Verify and contextualize the code

• Use a diagnostic scan tool to confirm P0237 is present, and check freeze-frame data for the recorded boost sensor signal and engine operating conditions (engine rpm, load, intake air temperature, etc.). Note any other codes that may point to sensor, wiring, or boost system issues.
• Confirm the code is not a one-off glitch (re-scan or retrieve pending codes if possible).

2) Perform a visual inspection

• Inspect the boost pressure sensor and its wiring harness for signs of damage, abrasion, oil/contamination, and secure mounting.
• Check the sensor connector for bent pins, corrosion, or loose pins; reseat and clean if needed.
• Inspect related vacuum/boost plumbing (intake manifold, intercooler hoses, intercooler piping, clamps) for cracks, leaks, or disconnections.

3) Electrical checks on the sensor circuit

• Verify power supply and ground:
  • Check that the Boost Sensor A is receiving the expected reference voltage (commonly a 5V reference from the PCM) and that the sensor ground is solid.
  • Inspect for any aged wiring that could cause a voltage drop or instability.
• Check for short to ground or short to voltage on the signal circuit:
  • With the ignition on (engine off, key in run position), observe the sensor signal circuit voltage. It should not be stuck at ground or a fixed rail if the sensor is healthy.
  • Look for any anomalous readings that could indicate a wiring fault or sensor fault.

4) Compare sensor signal to actual boost (functional test)

• With the engine running and under a controlled load (as permitted by safety), monitor the Boost Sensor A signal and compare it to actual boost pressure (if you have a mechanical or digital boost gauge or the PCM's live data of boost).
• If the sensor reports a low signal while boost pressure is high or commanded, this tends to indicate sensor/wiring issues rather than a mechanical boost failure.
• If actual boost is genuinely low, proceed to check the boost system (vacuum/boost leaks, wastegate control, turbocharger health) as the root cause.

5) Inspect the boost/vacuum system for leaks and integrity

• Check for leaks in hoses, intercooler piping, clamps, and the intake manifold. A leak could cause a lower-than-expected boost signal and trigger P0237.
• Inspect the wastegate actuator and boost control solenoids (where applicable) for proper operation.

6) Sensor and circuit testing

• If electrical checks indicate a solid power/ground and the signal circuit appears intact, test the sensor itself:
  • Swap in a known-good sensor if available to confirm whether the fault follows the sensor.
  • If the sensor is integrated with the manifold or wiring, inspect or replace the harness as needed.
• After any sensor replacement, re-check the circuit and monitor live data to confirm the signal now reads within expected range while the vehicle is under boost.

7) Evaluate corrective action

• If the sensor circuit is confirmed faulty, replace the Boost Sensor A (and, if appropriate, inspect and replace harness connectors). Reconnect and clear codes.
• If a boost leak or turbo system issue is found, repair the leak, replace hoses/ clamps, or service the turbo wastegate or intercooler system as required.
• If the actual boost is normal and the sensor/wiring is at fault, sensor or wiring replacement should resolve P0237.
• If the system has a genuine boost deficiency after repairs, re-test and verify that commanded boost matches actual boost; re-confirm no codes return.

8) Verify repair

• Clear the DTCs and perform a road test under normal driving conditions, paying attention to throttle response and boosted operation.
• Monitor live data for the Boost Sensor A signal and actual boost to confirm the problem is resolved.
• Ensure the CEL remains OFF after a successful test drive.

Tools Needed

• OBD-II scan tool capable of live data monitoring for boost sensor signals and related engine data.
• Basic electrical test tools (multimeter, test leads) for voltage, resistance, and continuity checks.
• Vacuum/boost system inspection tools as needed (smoke tester or equivalent for leaks, if available).
• Service information for your vehicle (to confirm exact sensor reference voltage, signal range, and wiring pinout).

Safety Considerations

• Turbo systems operate under pressure; never disconnect pressure lines while hot. Relieve boost pressure safely and follow vehicle-specific procedures.

• When working around electrical circuits and sensors, disconnect the battery when performing heavy electrical work as appropriate, and avoid shorting any circuits.

• Wear eye protection and follow standard shop safety practices when inspecting hoses, clamps, and turbo components.

• The explicit P0237 description from the Open Source code definition aligns with the standard interpretation of a low signal from Boost Sensor A.

• If you have access to NHTSA or manufacturer service data for P0237 in a particular vehicle, you can refine the cause probabilities accordingly for that model.

In short

• P0237 is a Turbo/Boost Sensor A Circuit Low fault. Start with a thorough electrical and visual inspection of the sensor, harness, and connectors, then verify the actual boost system (vacuum lines and wastegate control). Replace sensor or repair harness if needed, and fix any boost leaks or turbo issues if actual boost is insufficient. Verify by clearing codes and performing a road test with live data monitoring to ensure the fault does not recur.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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