P0236 Code: Turbo/Supercharger Boost Sensor A Range/Performance
The boost sensor's signal is electrically OK, but its readings don't make sense compared with other sensors.
At a glance
Severity: Moderate
- Meaning
- Turbo/Supercharger Boost Sensor A Range/Performance
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $5–$500
- DIY difficulty
- Moderate
With P0236 the boost pressure sensor circuit passes its electrical checks, yet the reading is implausible. The engine computer compares it with barometric pressure when the engine is off, with manifold pressure and airflow at idle, and with the boost it expects at a given load and rpm. If the sensor is offset, slow to respond or doesn't change when it should, this code sets. A sensor port gummed up with oily soot is a very common cause, but so is a real boost problem, because a leak or a sticking wastegate can make a perfectly good sensor look wrong. That's why the diagnosis starts by deciding whether the sensor or the boost itself is off.
Can I keep driving? Usually safe to drive gently, often with reduced power. Because the computer can't be sure of the true boost, avoid towing and sustained full throttle until it's fixed.
How to read P0236
- P Powertrain
- 0 Generic (SAE)
- 2 Fuel & air (injector circuit)
- 36 Specific fault
Symptoms
- Check engine light, sometimes with an underboost or overboost code
- Power that feels normal at part throttle but flat when you floor it
- Delayed turbo response, boost reading lagging behind engine speed
- Limp mode after highway driving or a long climb
- Boost value at rest that doesn't match outside air pressure
- Diesels: puffs of smoke on acceleration
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Sensor tip or port coated with oily soot, making it slow or offset
- Real boost problem (charge-air leak, sticking wastegate or vanes) making a good sensor look implausible
- Sensor drifted with age or heat
- Cracked, kinked or loose hose on remotely mounted boost sensors
- Wrong sensor pressure range after a replacement or tune
- Leaking sensor O-ring or cracked sensor boss on the charge pipe
- Extra resistance in the ground or signal wire skewing the voltage
Diagnosis step by step
Three-way comparison at key-on
With the key on and engine off, compare the boost sensor, MAP sensor (if separate) and barometric reading. All should agree within about 0.3 psi (2 kPa). If only the boost sensor is off, it's the prime suspect; if everything agrees, the fault probably shows up only under boost.
Tools: OBD-II scanner
Check the idle reading
On a gasoline engine the boost sensor usually sits before the throttle, so at idle it should read near barometric pressure while the MAP sensor shows vacuum. On a diesel without a throttle plate, both sit just above barometric at idle. A boost sensor showing vacuum or noticeable pressure at idle is suspect.
Tools: OBD-II scanner
Record response time under load
Graph engine speed, airflow and boost during a safe pull from about 1,500 rpm. Boost should start rising within a second of airflow increasing. A trace that lags, has flat steps or never exceeds a few psi while the turbo clearly spools points to a sluggish sensor.
Tools: OBD-II scanner
Pull and inspect the sensor
Remove the sensor and check the port for a tar-like coating and the O-ring for cracks. Clean only with sensor-safe electrical cleaner and a soft brush, without poking into the sensing hole. A split O-ring lets boost leak past the sensor and reads low.
Tools: Screwdriver, Soft brush
Pressure-test the sensor on the bench
Keep it plugged into the harness and pressurize it through a fitting with a regulated hand pump and gauge. Reading should climb in step with the gauge, for example 10 psi of applied pressure adding 10 psi to the scan tool value. A nonlinear or delayed response means replace the sensor.
Tools: Vacuum gauge, OBD-II scanner
If the sensor passes, chase the boost
A sensor that tests good means the deviation was real. Move on to a boost leak test at 15 to 20 psi and check the wastegate or vane actuator, since the same faults that cause P0299 or P0234 can trigger this code first.
Tools: Smoke machine
Where the parts are
- 1MAF sensor
- 2Turbocharger
- 3Throttle body
- 4Intake manifold
- 5Fuel injector
- 6EGR valve
- 7Fuel pump
- 8Thermostat
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Clean sensor port and replace O-ring | Yes | $5–$90 |
| Replace sensor hose on remote-mounted sensors | Yes | $10–$80 |
| Replace boost pressure sensor | Yes | $80–$320 |
| Repair boost leak found during testing | No | $50–$500 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Field data
| Ford | 6 | Escape, Focus Bev, Explorer | |
|---|---|---|---|
| Hyundai | 2 | Accent, Sonata |
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
Emissions stations in OBD-II testing states fail a vehicle with the check engine light on. Clear only after the repair and let the monitors finish, or the car will be turned away as not ready.
Frequently asked questions
How can a good sensor set P0236?
The computer only knows the reading is implausible, not why. If boost really is too low or too high because of a leak or a stuck wastegate, the sensor can report accurately and still fail the plausibility check. Testing the sensor first avoids buying one you don't need.
Can I clean a boost sensor?
Yes, if it's just coated with oily soot. Use electrical contact cleaner, a soft brush and patience, and never push anything into the sensing port. If it still reads off afterward, replace it.
Does a tune cause P0236?
It can if the tuner fitted a higher-range sensor but didn't rescale the calibration, or the other way around. The computer then misreads the voltage and the numbers no longer agree with baro and airflow.
Will the car pass inspection after I clear the code?
Not immediately. Clearing resets the readiness monitors, and most testing programs reject a car until they've completed. Drive a mix of city and highway for a few days after the repair.