EN

Severity: Moderate Code type: Generic (all makes)

P0237 Code: Turbo/Supercharger Boost Sensor A Circuit Low

The boost sensor signal has dropped near zero volts, reading less pressure than the atmosphere can provide.

At a glance

Severity: 3/5 – Moderate3/5

Severity: Moderate

Meaning
Turbo/Supercharger Boost Sensor A Circuit Low
System
Fuel & Air Metering · Powertrain
Safe to drive?
With caution
Typical repair cost
$0–$1,800
DIY difficulty
Easy

A boost pressure sensor reports roughly barometric pressure with the engine off, which on most sensors is somewhere in the lower part of its 0.5 to 4.5 volt range. P0237 sets when the signal falls below the bottom of that window, typically under a few tenths of a volt. That would mean pressure far below atmospheric in a pipe that is supposed to be pressurized, so the ECU knows the reading is electrical, not real. It can't simply trust it either: a near-zero boost reading would make it chase boost the engine already has, so it drops into limp mode with the turbo held at low output. The cause is usually a lost 5-volt reference, a signal wire open or shorted to ground, an unplugged or oil-soaked connector, or a failed sensor.

Can I keep driving? The car will usually drive but with little power, which makes merging and passing risky. Drive gently to a shop; if several sensor codes appear at once or the accelerator pedal stops responding properly, have it towed.

How to read P0237

How to read P0237P10223374
  1. P Powertrain
  2. 0 Generic (SAE)
  3. 2 Fuel & air (injector circuit)
  4. 37 Specific fault

Symptoms

  • Sudden loss of power and limp mode, often with the turbo barely building boost
  • Boost reading in scan data near zero or far below barometric pressure with the engine off
  • Other sensor codes at the same time (pedal, rail pressure, MAP) if a shared 5-volt reference is down
  • Black smoke on diesels as fueling and boost no longer match
  • Power returns after a restart, then drops again as soon as the fault reappears

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Sensor connector unplugged or not latched after intercooler hose or turbo work 22%
  2. 5-volt reference pulled down by a short in another sensor sharing the same circuit 20%
  3. Signal wire open or chafed to ground near the charge pipe or intercooler 18%
  4. Boost sensor failed internally, often after oil from the charge pipe soaked into it 18%
  5. Corroded or oil-contaminated terminals 12%
  6. Wrong sensor or wrong pinout after a repair 6%
  7. ECU input or reference driver fault 4%

Diagnosis step by step

Diagnostic flow: P02371Compare boost and barometricreadings, key on2Check the other codes stored3Measure reference, ground and signal4Inspect the plug and the pipe5Check the signal wire end to end6Fit the correct sensor and testunder boost

  1. Compare boost and barometric readings, key on

    With the engine off and key on, the boost sensor should read the same as barometric pressure, about 14.7 psi absolute near sea level. If boost shows near zero while baro or MAP looks normal, the problem is in the boost sensor circuit; if everything on the same reference reads low, go straight to the 5-volt supply.

    Tools: OBD-II scanner

  2. Check the other codes stored

    Codes for the accelerator pedal, rail pressure or a reference voltage (such as P0641) along with P0237 mean a shared 5-volt circuit is being pulled down. Unplug the sensors on that circuit one at a time; when the reference jumps back to 5 V, the last one unplugged is shorted.

    Tools: OBD-II scanner, Multimeter

  3. Measure reference, ground and signal

    Back-probe the connector with the key on: reference about 5 V, ground under 0.1 V, signal roughly 1 to 2 V at atmospheric pressure on many sensors. Good reference and ground but near-zero signal points to the sensor or an open or grounded signal wire.

    Tools: Multimeter

  4. Inspect the plug and the pipe

    Look for a connector that isn't clicked in, oil inside it, or green corrosion. If the charge pipe is oily around the sensor, fix the crankcase ventilation or turbo seal problem too, or the new sensor will fail the same way.

    Tools: Flashlight, Soft brush

  5. Check the signal wire end to end

    With the battery disconnected and ECU unplugged, measure signal wire continuity from sensor to ECU (well under 1 ohm) and from signal to ground (it should read open). Flex the harness where it runs along the intercooler piping during the test.

    Tools: Multimeter

  6. Fit the correct sensor and test under boost

    Install the sensor specified for your engine, clear codes and road test. Boost should rise smoothly on acceleration, and the reading should return to barometric pressure with the engine off.

    Tools: OBD-II scanner

Where the parts are

Ignition: coils and spark plugs per cylinder – P02371234567
Ignition: coils and spark plugs per cylinder
  1. 1Ignition coil
  2. 2Spark plug
  3. 3Fuel injector
  4. 4Camshaft sensor
  5. 5Crankshaft sensor
  6. 6Engine computer (ECM)
  7. 7Intake manifold

Repair options & costs

RepairDIY?Estimated cost
Reconnect or replace the sensor connector Yes $0–$150
Replace boost pressure sensor Yes $80–$300
Repair signal wire or shared 5-volt reference No $120–$450
Replace a shorted sensor on the shared reference No $80–$400
Fix oil in the charge pipe (PCV or turbo seal) No $150–$1,800

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Emissions / smog test impact

Will fail

P0237 turns on the check engine light, which fails an OBD-II emissions test, and many diesel inspections also check the readiness of boost-related monitors. Repair it, then drive until the monitors have completed.

Frequently asked questions

Why does a low reading put the engine into limp mode?

If the ECU believed a near-zero boost reading, it would keep asking the turbo for more pressure the engine already has. To avoid overboosting, it ignores the sensor and holds boost at a safe, low level.

What's the difference between P0237 and P0238?

P0237 is a signal stuck too low, usually an open, a short to ground or a lost 5-volt reference. P0238 is the opposite, a signal stuck too high from an open ground or a short to voltage.

Why did P0237 show up after my intercooler job?

The boost sensor usually sits on the charge pipe or intake manifold and its plug is easy to knock loose or leave unlatched. Check that first; it's the cheapest fix there is.

Can a bad throttle pedal cause P0237?

Indirectly, yes. On many engines the pedal sensor shares the 5-volt reference with the boost sensor. A short inside the pedal can drag that reference down and set codes on everything connected to it.

Sources