P0237: Turbocharger / Supercharger Boost Sensor 'A' Circuit Low
Diagnostic Trouble Code (DTC) P0237 indicates that the Engine Control Module (ECM/PCM) has detected that the electrical voltage signal from the Manifold Absolute Pressure (MAP) / Boost Pressure Sensor 'A' has dropped below the minimum calibrated threshold (typically < 0.20V to 0.25V DC) for a duration exceeding calibrated monitor limits. In modern common rail turbo-diesel engines, the ECM depends on this continuous analog signal to meter boost pressure and regulate fuel injection delivery. A voltage reading below 0.20V is physically impossible under running conditions (representing a pressure lower than an absolute deep space vacuum), indicating a broken signal wire, an internal open circuit, a short circuit to ground, or a loss of the regulated 5.0V reference supply.
🚗 Operational Safety, Typical Repair Costs & Diagnostic Verification
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🚦 Driving Safety & Operational Risk
Immediate mechanical assessment and tow requirementsSafe to drive carefully in Limp Mode to a workshop, but acceleration is severely crippled.
DTC P0237 indicates that the Manifold Absolute Pressure (MAP) / Boost Sensor signal voltage has dropped below 0.2V (typically registering 0.0V). Because the ECU receives an impossible zero-voltage reading, it assumes a complete sensor circuit failure or broken wiring. As a fail-safe precaution, the ECU disables turbo boost regulation and caps fueling to prevent engine damage. While you will not damage the engine by driving gently, merging into high-speed highway traffic is hazardous due to the lack of power.
MECHANICAL HAZARDS & ENGINE RISK IF DRIVEN:Extremely slow acceleration creates serious collision risks when merging onto fast motorways; unmetered fueling under load can cause heavy exhaust smoke. - 02
💰 Typical Workshop Repair Budget
Expected parts replacement and garage labor cost tiersMinor DIY / Filter Purge$25 - $75: Repairing broken or chafed sensor signal wire, reconnecting loose plug, or cleaning corroded connector pins.Sensor cleaning, fuel filter renewal, fuse replacement, or harness contact cleaning.
Sensor / Valve Replacement$85 - $220: Brand-new genuine OEM Bosch / Continental 3-bar or 4-bar MAP boost pressure sensor replacement.Single component fix (e.g. pressure regulator valve, inlet metering unit, or reconditioned injector).
Major Overhaul / Pump & Injectors$350 - $700: Engine bay wiring harness repair or electronic turbocharger variable vane actuator check.High-pressure injection pump overhaul, new OEM injector set, or DPF assembly replacement.
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🧰 Initial Visual & Physical Verifications
5-minute zero-tool garage triage steps before calling a workshop1Inspect the MAP sensor plug on the intake pipe or manifold: Verify if the connector has vibrated loose or if the locking tab is snapped.2Examine the wire loom near the radiator fan and metal brackets: Check for wire chafing or signs of rodent chewing.3Read OBD live data with Key-ON Engine-OFF: Read boost pressure. If it reads 0 kPa / 0.0 bar (normal ambient is ~100 kPa / 1.0 bar), the signal line is open or shorted to ground. - 04
🛡️ Diagnostic Verification & Mechanic Shield
Exact questions to ask your technician to prevent unnecessary parts replacement"Ask the technician: 'With the sensor disconnected, did you measure the 5V reference voltage on the harness plug before condemning the sensor?'"
"Require the technician to verify wire continuity between the sensor connector and the ECU before quoting an expensive turbocharger replacement."
"If you have an aftermarket piggyback tuning box installed, unplug it first; over 70% of P0237 codes stem from faulty harness jumpers."
Technical Note: Read these technical questions to your mechanic before approving expensive parts replacements:
30-Second Workshop Triage
- Check Engine Light (MIL) illuminated continuously on the dashboard
- Severe loss of engine power, sluggish throttle response, and inability to accelerate past highway speeds
- Vehicle locked in Limp-Home mode with engine speed capped (typically below 3,000 RPM)
- Severed, broken, or open MAP sensor signal wire between the sensor connector and the ECM
- MAP sensor signal wire pinched or chafed directly to engine metal ground
- Loss of the regulated 5.0V reference voltage supply from the Engine Control Module
Connect scan tool live telemetry: compare Target Fuel Rail Pressure vs Actual Rail Pressure and log metering valve command PWM duty cycle during idle and road load.
Expensive Diagnostic Pitfall & Technical Reality
P0237 means the turbocharger has completely blown its compressor wheel or seized, requiring an immediate new turbocharger replacement ($1,400 - $2,500).
P0237 is purely an electrical low-voltage DTC indicating that the Manifold Absolute Pressure (MAP) sensor signal wire voltage has dropped below 0.20V. In a functioning sensor at sea level, atmospheric pressure yields approximately 1.6V (for a 3-bar sensor) with engine off. A 0.1V reading signifies that the 5V reference feed wire is broken, the sensor signal pin is shorted directly to chassis ground, or the sensor connector plug has fallen off. The turbocharger itself is completely intact.
Spending $1,800+ replacing a healthy Garrett/BorgWarner turbocharger vs repairing a broken $10 harness wire or cleaning the connector plug, saving over $1,700.
Most Common Engines & Fuel Injection Platforms Affected
This fault code predominantly affects the following common rail diesel platforms. Cross-reference your specific engine family below for verified factory failure modes, key sub-assembly part numbers, and dedicated repair links:
VAG 2.0 TDI (EA189 / EA288 Common Rail)
Typical Symptom: Flashing glow plug coil icon on cluster, complete loss of turbo boost, vehicle stuck in 45 mph limp home mode
Known Factory Failure Mode: MAP sensor 4-pin connector water corrosion, or 5V reference supply wire open circuit dropping signal voltage to 0.0V
OE 038906051K / Bosch 0 281 002 401 3-Bar / 4-Bar Manifold Absolute Pressure SensorFord / PSA 1.6 TDCi (DV6ATED4 / DV6TED4)
Typical Symptom: Car feels completely sluggish and powerless under load, Check Engine MIL on, unable to accelerate on hills
Known Factory Failure Mode: Engine wiring loom rubbing against sharp edge of metal EGR heat shield, shorting sensor signal wire directly to vehicle ground
OE 9639381480 / Bosch 0 261 230 043 Boost Pressure SensorBMW 2.0d / 3.0d (N47 / N57 / M47N)
Typical Symptom: Drivetrain malfunction on dashboard, instant electronic boost cut, vehicle sluggish like an unboosted diesel
Known Factory Failure Mode: Internal piezoresistive silicon diaphragm fracture within MAP sensor body or pin terminal back-out inside plug
OE 13627792260 / Bosch 0 281 002 961 Intake Manifold Pressure SensorMercedes-Benz 2.1 CDI (OM651)
Typical Symptom: Van speed capped at 80 km/h, harsh transmission shifts, check engine light illuminated, P0237 active in ECU
Known Factory Failure Mode: Charge air pipe pressure sensor wiring loom pinched near coolant expansion tank bracket, breaking 5V reference wire
OE A0061539928 / Bosch 0 281 002 844 Boost Pressure SensorDiesel Boost Pressure Sensor (MAP) Diagnostics Guide
Workshop diagnostic guide for turbo boost sensor fault codes P0236, P0237, and P0238. Manifold pressure testing, 5V reference, and VNT vane correlation.
Control Circuit & Actuator Logic
1. Dynamic In-Demand Fuel Metering
The MAP / Boost Pressure Sensor 'A' operates on a 3-wire analog interface: (1) 5.0V regulated reference supply from the ECM; (2) Sensor analog ground return; (3) Analog signal output. Normal operational voltage ranges between 0.50V (low absolute pressure) and 4.50V (maximum boost pressure). The ECM analog input circuit features an internal pull-down resistor (or lacks a pull-up). Consequently, if the wiring harness is disconnected, a wire breaks, or the signal line contacts vehicle chassis metal, the input pulls straight to 0.00V, immediately flagging DTC P0237.
2. Closed-Loop PID Deviation Monitoring
The ECM continuously samples the MAP signal channel via a 10-bit or 12-bit Analog-to-Digital Converter (ADC). If the signal voltage remains below 0.20V for more than 200-500 milliseconds, the ECM registers a circuit low fault. The ECM immediately substitutes a calibrated substitute default MAP value (typically atmospheric baseline 100 kPa), disables dynamic VNT vane regulation, restricts fuel injection quantity, and triggers Limp-Home mode to prevent severe engine damage.
3. Diagnostic Trap: Normally Open (NO) vs Normally Closed (NC) Valves
Open Signal Wire vs Short to Ground: If P0237 is present, disconnecting the sensor and measuring harness voltages isolates the fault: if 5V reference is intact (> 4.95V) and ground is intact (< 0.05V drop), jumping the 5V reference to the signal pin with a 1 kΩ resistor should drive the scan tool reading to ~5.0V. If it does, the wiring is sound and the sensor has an internal open circuit. If the reading remains at 0.00V, the signal wire is shorted to ground or severed.
Electrical & Hydraulic Physical Benchmarks
Step-by-Step Workshop Diagnostic Protocol
Scan Tool Live Data Voltage Verification
Connect a professional scan tool, switch ignition ON, and navigate to Live Data -> Manifold Absolute Pressure (MAP) Sensor 'A' Voltage. Observe the live voltage. If the PID displays < 0.20V (typically 0.00V or 0.04V), DTC P0237 is confirmed active. Note whether MAP pressure is reading an impossible zero or a substitute default value.
Measure 5.0V Reference Supply at Sensor Harness Connector
Disconnect the MAP sensor connector. Turn ignition ON (engine OFF). Using a calibrated digital multimeter referenced to battery negative, measure voltage on the 5V reference pin in the harness plug. The reading must be between 4.95V and 5.05V DC. If reading 0V, inspect the 5V feed wire for open circuit or short to ground back to the ECM.
Verify Sensor Ground Circuit Voltage Drop & Continuity
With the connector unplugged and ignition ON, measure voltage drop between the sensor ground pin and the battery negative terminal. The drop must not exceed 0.05V (50 mV). Turn ignition OFF and measure resistance between the ground pin and chassis ground (must be < 0.4 Ω). Ensure no high-resistance corrosion exists on the ground circuit.
Signal Circuit Jumper Bypass Test
With ignition ON and connector unplugged, insert a 1 kΩ fused jumper wire between the 5V reference terminal and the signal wire terminal in the harness connector. Observe the scan tool live data. If the voltage jumps from 0.00V to approximately 4.8V-5.0V, the wiring harness and ECM input circuit are 100% functional, confirming that the MAP sensor itself has suffered an internal open circuit.
Harness Continuity & Short-to-Ground Test
Disconnect the main harness connector from the ECM. Using a digital multimeter on the 200 Ω scale, measure resistance on the signal wire between the ECM pin and the sensor plug (must read < 0.4 Ω). Then test resistance between the signal wire and chassis ground (must read infinite resistance / OL). Any measurable resistance to ground indicates an insulation breach.
Inspect Connector Pins for Terminal Spread & Moisture
Inspect the female terminal pins inside the MAP sensor plug using an inspection mirror and bright light. Verify terminal retention drag with an OEM test pin. Check for water intrusion, silicone seal degradation, or green copper oxide corrosion.
Component-Level BOM: Charge Air Manifold Absolute Pressure (MAP) Sensor Circuit
Charge Air Manifold Absolute Pressure (MAP) Sensor Circuit
0 281 002 976 / 0 281 006 059
Measures intake manifold pressure and air charge temperature for ECU boost regulation
1J0 973 704 / Kostal 4-Way MLK 1.2
Provides positive terminal spring tension on vibrating intake manifold
N 909 277 02 / OEM High-Temp O-Ring
Prevents boost pressure leaks around sensor mounting boss
MAP Sensor Voltage-to-Boost Calibration Chart
High-Pressure Pump Adaptation Reset & Road Test Drive Cycle
Following the repair of the wiring harness, terminal repair, or replacement of the MAP sensor for DTC P0237:
1. Clear all trouble codes from the Engine Control Module memory using a scan tool.
2. Access ECM Special Functions -> 'Reset Boost Pressure Sensor Adaptation / Offset Values'.
3. Switch ignition OFF and leave undisturbed for 60 seconds to allow the ECM main relay to power down and save non-volatile memory.
4. Switch ignition ON for 10 seconds (engine OFF) to allow the ECM to calibrate the new sensor's zero-point barometric reading.
5. Start the engine and verify that live MAP voltage displays ~1.65V-1.85V at idle, followed by a dynamic road test verifying smooth boost tracking.
Differential Diagnosis & Related Faults
Workshop Field Case Studies
2016 Volkswagen Passat 2.0 TDI (CRLB)(162,000 km)
Frequently Asked Technical Questions
What does engine fault code P0237 mean?
Diagnostic Trouble Code (DTC) P0237 indicates that the Engine Control Module (ECM/PCM) has detected that the electrical voltage signal from the Manifold Absolute Pressure (MAP) / Boost Pressure Sensor 'A' has dropped below the minimum calibrated threshold (typically < 0.20V to 0.25V DC) for a duration exceeding calibrated monitor limits. In modern common rail turbo-diesel engines, the ECM depends on this continuous analog signal to meter boost pressure and regulate fuel injection delivery. A voltage reading below 0.20V is physically impossible under running conditions (representing a pressure lower than an absolute deep space vacuum), indicating a broken signal wire, an internal open circuit, a short circuit to ground, or a loss of the regulated 5.0V reference supply.
What are the most common symptoms of P0237?
Check Engine Light (MIL) illuminated continuously on the dashboard, Severe loss of engine power, sluggish throttle response, and inability to accelerate past highway speeds, Vehicle locked in Limp-Home mode with engine speed capped (typically below 3,000 RPM), Noticeable turbo lag and total absence of turbocharger boost boost spool noise, Inability of the vehicle to climb moderate uphill grades under load, Scan tool live data displays MAP sensor voltage pegged at 0.00V (or reported pressure default of 0 kPa or 100 kPa fixed).
What causes P0237 on a diesel engine?
Severed, broken, or open MAP sensor signal wire between the sensor connector and the ECM; MAP sensor signal wire pinched or chafed directly to engine metal ground; Loss of the regulated 5.0V reference voltage supply from the Engine Control Module; Corroded, oxidized, or spread female terminal pins in the MAP sensor electrical connector; Internal failure or open circuit in the silicon piezoresistive element inside the MAP sensor; Defective Analog-to-Digital Converter (ADC) input channel inside the Engine Control Module (ECM).
Is it safe to drive with code P0237 active?
🟡 Caution: Limp Mode Active / Service Soon
How much does it cost to fix fault code P0237?
Typical repair costs for fault code P0237 depend on the underlying root cause and diagnostic tier: Level 1 (Minor / Maintenance): $25 - $75: Repairing broken or chafed sensor signal wire, reconnecting loose plug, or cleaning corroded connector pins. (Sensor cleaning, fuel filter renewal, fuse replacement, or harness contact cleaning.); Level 2 (Component Replacement): $85 - $220: Brand-new genuine OEM Bosch / Continental 3-bar or 4-bar MAP boost pressure sensor replacement. (Single component fix (e.g. pressure regulator valve, inlet metering unit, or reconditioned injector).); Level 3 (Major Sub-Assembly): $350 - $700: Engine bay wiring harness repair or electronic turbocharger variable vane actuator check. (High-pressure injection pump overhaul, new OEM injector set, or DPF assembly replacement.). Independent workshop benchmark rates. Data indicates over 70% of occurrences are resolved within Level 1 or Level 2 without replacing entire sub-assemblies.
Can a blown fuse cause DTC P0237?
Generally no. The 5.0V reference supply for the MAP sensor is generated directly by an internal voltage regulator chip inside the ECM, not through a conventional fuse. However, if a blown engine management fuse cuts battery power to the entire ECM, multiple communication and sensor codes will occur.
Why does my car feel like it has no turbocharger when P0237 is active?
When the ECM loses the MAP signal (< 0.20V), it cannot determine boost pressure. To protect the engine from overboost and thermal runaway, it engages Limp-Home mode, commands the VNT turbo actuator to dump all boost, and drastically cuts injected fuel quantity.
How do I know if the MAP sensor or the ECM is bad?
Perform the 1 kΩ jumper test: bridge the 5V reference wire to the signal wire at the unplugged sensor connector. If the scan tool shows the signal voltage jump from 0.0V to ~5.0V, the ECM input circuit and wiring harness are 100% good; the MAP sensor is internally open and must be replaced.