Open circuit or short to voltage in the cylinder 4 pressure sensor signal wiring; Corroded, damaged or loose connector at the cylinder 4 pressure sensor; Faulty cylinder 4 pressure sensor; Fault in the sensor reference voltage supply or ground, possibly shared with other cylinder sensors; Sensor contaminated or fouled by carbon deposits (depends on engine design); Internal fault in the engine control unit or its sensor input.

P03B6

Cylinder 4 Pressure Sensor Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
B6: FaultThe specific fault in that area

What it means

P03B6 is the SAE J2012 generic code for a high input in the cylinder 4 pressure sensor circuit. The engine control unit monitors the in-cylinder pressure sensor signal and saw a voltage above the expected range for longer than the allowed time. This points to a fault in the sensor, its wiring or its supply, rather than a confirmed mechanical problem in the cylinder.

Symptoms

Engine warning light on
Rough running or misfire on cylinder 4
Reduced power or the engine running in a limited mode
Poor fuel economy
Rough idle or hesitation under load
Possible difficulty starting on some engines

Possible causes

Open circuit or short to voltage in the cylinder 4 pressure sensor signal wiringlikely
Corroded, damaged or loose connector at the cylinder 4 pressure sensorlikely
Faulty cylinder 4 pressure sensorlikely
Fault in the sensor reference voltage supply or ground, possibly shared with other cylinder sensorspossible
Sensor contaminated or fouled by carbon deposits (depends on engine design)possible
Internal fault in the engine control unit or its sensor inputrare

How to diagnose

Read all stored codes and freeze frame data, noting engine speed, load and temperature when the fault set, and check for related codes on other cylinders or sensor supplies.
Look at the cylinder 4 pressure sensor, its connector and the wiring for chafing, heat damage, oil contamination, bent pins or corrosion.
Clear the code and see if it returns immediately or only under certain conditions, wiggling the harness while watching live data.
Check live data for the cylinder 4 pressure signal and compare it with the other cylinders, if the car provides them.
Using the manufacturer wiring diagram, check the sensor reference supply, ground and signal wire for continuity, and for a short to voltage or to each other.
Measure the supply voltage and signal voltage at the sensor connector with the ignition on, comparing with the specified values for that engine.
Check for any software update or technical bulletin for the model and engine, as procedures and sensor type vary.
If wiring and supply are good, test or substitute the sensor in line with the manufacturer's procedure.

How to fix

Repair or replace damaged wiring, correcting any short to voltage or open circuit.
Clean, repair or replace faulty connector terminals and secure the connector properly.
Replace the cylinder 4 pressure sensor if it fails testing, following the specified fitting and torque procedure.
Restore the correct reference supply or ground if the fault is in a shared circuit.
Update the engine control unit software only if a known outdated calibration is documented as the cause, or replace the control unit if proven faulty.

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but book it in soon as combustion monitoring may be reduced and the engine could run poorly. Stop driving if it runs very roughly, misfires badly or loses significant power.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.