Drivable short-term in limp mode, but power and boost stay limited; repair the circuit soon so normal boost control returns and to avoid being caught with reduced power. P0237 means the engine computer saw the turbocharger (or supercharger) boost-pressure sensor 'A' signal sitting too low, below its normal working range. It is an electrical circuit fault, most often a signal wire shorted to ground or an open in the circuit, not necessarily a real loss of boost.
What P0237 means
A forced-induction engine relies on a boost-pressure sensor to tell the powertrain control module (PCM) how much pressure the turbo or supercharger is building in the intake tract. On many engines this is a dual-function pressure-and-temperature unit mounted in the charge-air tube between the intercooler (charge air cooler, or CAC) and the throttle body. It is typically a three-wire sensor fed a 5-volt reference, returning a signal that rises with pressure and sharing a ground. P0237 sets when the PCM reads the boost-sensor signal voltage below its expected floor, which the module interprets as an out-of-range 'circuit low' condition. In electrical terms that points to the signal wire shorted to ground, an open in the signal or reference circuit that pulls the reading toward zero, or a sensor that has failed internally and pins its output low. It is monitored with the key on and engine off, key on and engine running, and continuously, and typically forces reduced-power fail-safe operation so boost is limited until the fault clears.
Symptoms
- Check-engine light on, often stored in continuous (KAM) memory
- Reduced engine power or a limp/fail-safe mode that caps boost
- Sluggish acceleration and poor throttle response, especially under load
- Noticeably weak or absent turbo/supercharger boost and slow pickup
- Possible rough running, hesitation, or occasional stumble when accelerating
Common causes
- Boost-pressure (TCBP) signal circuit shorted to ground
- Failed turbocharger boost-pressure/charge-air-temperature (TCBP/CACT) sensor pinning its signal low
- Open or high-resistance in the signal or 5V reference wire pulling the reading toward zero
- Corroded, loose, or damaged sensor connector with spread or pushed-back terminals
- Chafed, pinched, or melted harness wiring making contact with ground or a nearby component
- Moisture or oil intrusion in the connector bridging the signal to ground
- Rarely, a PCM/driver fault or a reference-voltage problem on the shared circuit
Severity & driving advice
Severity: Moderate — Not an immediate hazard, but the engine usually drops into reduced-power limp mode with capped boost until the sensor circuit is fixed.
Can I drive? Drivable short-term in limp mode, but power and boost stay limited; repair the circuit soon so normal boost control returns and to avoid being caught with reduced power.
Diagnostic approach
- Read codes and check live boost-sensor data — Scan for all stored and pending codes and record the freeze-frame conditions. With a scan tool, watch the boost/charge-air pressure sensor's live voltage and pressure reading. Key-on engine-off it should sit near barometric pressure with a low-to-mid signal voltage; a value stuck near 0V, or reading zero/minimum pressure that never rises when the engine builds boost, confirms a circuit-low condition rather than a genuine loss of boost.
- Inspect the sensor, connector, and wiring — Locate the TCBP/CACT sensor on the intake air tube between the charge air cooler and the throttle body. Unplug it and inspect for corrosion, bent or spread terminals, moisture, or oil. Follow the harness looking for chafing, pinches, or melting where it could contact ground or hot components. Backprobe the connector while wiggling the harness to expose an intermittent short-to-ground that sets the code, since Ford's diagnostic aid flags intermittent harness contact as a common cause.
- Test the signal circuit for a short to ground — With the sensor unplugged and the key on, measure the signal wire voltage: it should float up near the 5V reference with nothing connected. If the disconnected signal wire still reads near 0V, the circuit is shorted to ground upstream of the sensor. Turn the key off and check resistance from the signal wire to ground and to chassis; a near-zero reading confirms the short that trips P0237.
- Verify the 5V reference and ground — Key on, back-probe the connector and confirm roughly 5 volts on the reference wire and a clean ground (near 0V) at the sensor. An open or high-resistance reference wire can drop the sensor's available supply and force the signal low. Check continuity of the reference and ground circuits back toward the PCM to rule out an open that starves the sensor.
- Confirm the sensor itself — If the wiring, reference, and ground all check out, the sensor is the likely fault. Confirm with a known-good sensor or by verifying the signal responds correctly to applied vacuum/pressure. Compare the sensor's voltage-versus-pressure behavior to spec: the signal should climb smoothly with pressure rather than stay pinned at its low limit.
- Repair, clear, and road-test — Repair the shorted wire, connector, or sensor as found. Clear the code and drive the vehicle through a boost cycle while monitoring sensor voltage and reported boost. Confirm the signal tracks actual charge pressure and that fail-safe/limp mode no longer engages, then recheck continuous-memory codes to be sure P0237 does not reset.
FAQ
Does P0237 mean my turbo is bad?
Usually not. P0237 is a boost-pressure sensor circuit fault, meaning the sensor's signal read too low electrically. It points at the sensor, its connector, or a wire shorted to ground far more often than at the turbocharger itself. Diagnose the circuit before replacing any hardware.
What is the difference between P0237 and P0238?
They are the two out-of-range ends of the same boost-sensor circuit. P0237 is 'circuit low' (signal too low, typically a short to ground or an open in the signal/reference), while P0238 is 'circuit high' (signal too high, usually a short to voltage or an open ground). Both normally cap boost until repaired.
Can I drive with a P0237 code?
You can usually drive short distances, but the engine typically drops into reduced-power fail-safe mode with limited boost, so it will feel sluggish. It is not an immediate safety hazard, but you should have the sensor circuit repaired soon so full power and normal boost control return.
How do I test the boost-pressure sensor for P0237?
With a scan tool, watch the sensor's live voltage and pressure with the key on; a value stuck near zero suggests a circuit-low fault. Unplug the sensor and check that the disconnected signal wire floats up toward the 5V reference rather than staying at 0V, which would reveal a short to ground. Then confirm about 5 volts of reference and a clean ground at the connector. If the wiring and grounds are good but the signal stays pinned low, the sensor is the likely fault.
Where is the boost-pressure sensor located?
On many turbocharged engines, including Ford's 3.5L EcoBoost, the boost-pressure sensor is a combined pressure-and-temperature unit (Ford calls it the TCBP/CACT sensor) mounted in the charge-air tube between the intercooler (charge air cooler) and the throttle body. Its job is to report the actual pressure and temperature of the compressed intake air to the PCM.