Engine

P03A3 — Cylinder 2 Pressure Sensor Signal Intermittent or Erratic

Severity: medium Drive with care, to a shop

What P03A3 means

The engine control module monitors the cylinder 2 pressure sensor, which reports how combustion is developing in that cylinder. P03A3 sets when the signal drops out, jumps around or falls outside the expected range. The cause is usually the sensor, damaged wiring or a poor connection, and occasionally the control module itself.

Symptoms

  • Check Engine light on
  • Rough running or misfire-like symptoms
  • Unstable idle
  • Worse fuel economy
  • Reduced power

Possible causes

  1. Failed cylinder 2 pressure sensor
  2. Broken, chafed or corroded wiring in the sensor circuit
  3. Loose or corroded sensor or ECM connector
  4. Secondary engine problem such as a cylinder 2 misfire or fuel delivery issue
  5. ECM fault or software issue (uncommon)

How to diagnose

  1. Scan for all codes and freeze frame data, and look for related cylinder 2 or misfire codes
  2. Inspect the sensor harness and connector for damage, moisture, corrosion and rubbing
  3. Wiggle the harness with the engine running and watch the sensor signal on a scan tool
  4. Check sensor power, ground and reference voltage against the factory wiring diagram
  5. Test the signal wire for opens and shorts to ground or power
  6. Check the cylinder 2 spark plug, coil and injector to rule out a real misfire
  7. Compare the sensor reading with the other cylinders if the scan tool supports it
  8. Look for ECM software updates or service bulletins

Common fixes

  • Repair damaged wiring and clean or replace the connector
  • Replace the cylinder 2 pressure sensor
  • Fix the underlying misfire or fuel issue if one is found
  • Update or reflash the ECM per manufacturer instructions

Questions and answers

What does P03A3 mean?

The ECM detects an intermittent or erratic signal from the cylinder 2 pressure sensor. Wiring, the connector or the sensor itself are the usual culprits.

Can I drive with P03A3?

Briefly and carefully if the engine runs smoothly. If it misfires or the Check Engine light flashes, stop driving and have the car towed.

How do I fix P03A3?

Start by inspecting the sensor wiring and connector, then test power, ground and signal. If those are good, replace the sensor, and consider an ECM update last.

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.