Engine

P03A2 — Cylinder 2 Pressure Sensor Circuit High

Severity: medium Drive with care, to a shop

What P03A2 means

The engine control module monitors the voltage in the cylinder 2 pressure sensor circuit. This sensor measures combustion pressure and helps fine-tune fuel injection and ignition timing. P03A2 sets when the signal rises above the expected range, due to a bad sensor, a short to voltage in the wiring, or, rarely, a module fault.

Symptoms

  • Check Engine light on with P03A2 stored
  • Rough or unstable idle
  • Hesitation or stumbling under acceleration
  • Reduced power (varies by vehicle)
  • Higher fuel use and emissions

Possible causes

  1. Failed cylinder 2 pressure sensor
  2. Signal wire shorted to voltage
  3. Corroded or damaged sensor connector
  4. Chafed or damaged wiring harness
  5. Fault in the sensor reference voltage supply
  6. Engine control module failure (rare)

How to diagnose

  1. Scan all codes and freeze frame data, clear P03A2 and see whether it returns
  2. Inspect the cylinder 2 sensor connector and harness for damage, moisture, rubbing and corrosion
  3. Check the connector's power, ground and signal wires against the factory wiring diagram
  4. With the sensor unplugged, test the signal circuit for a short to voltage
  5. Watch the sensor reading on a scan tool with the engine off and running
  6. Test the sensor per the manufacturer's procedure or swap in a known good one
  7. If the wiring and sensor are fine, check the control module and its software

Common fixes

  • Replace the cylinder 2 pressure sensor
  • Repair or replace the damaged wiring section
  • Clean or replace the connector and terminals
  • Replace or reflash the control module, only after diagnosis confirms it

Questions and answers

What does P03A2 mean?

The engine computer detected a too-high signal in the cylinder 2 pressure sensor circuit. The usual cause is the sensor itself or a short to voltage in the wiring.

Can I drive with P03A2?

Briefly and with care, yes, but the engine may run rough and lose power. Don't put off the diagnosis.

How do I fix P03A2?

Start by checking the cylinder 2 sensor connector and wiring, then the sensor. Replace the control module only as a last resort.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.