Engine

P03DB — Cylinder 8 Pressure Sensor Circuit Fault

Severity: medium Drive with care, to a shop

What P03DB means

Some engines use in-cylinder pressure sensors so the ECM can monitor combustion and fine-tune fueling and timing. P03DB is set when the signal from the cylinder 8 sensor is missing, erratic or out of range. The problem may be the sensor, its wiring or the ECM input.

Symptoms

  • Check Engine light on
  • Rough idle
  • Reduced power or sluggish throttle response
  • Higher fuel consumption
  • Possible limp mode

Possible causes

  1. Failed or contaminated cylinder 8 pressure sensor
  2. Open, shorted or chafed sensor wiring
  3. Corroded terminals or a loose connector
  4. Missing sensor supply voltage or ground
  5. ECM fault (rare)

How to diagnose

  1. Scan all codes and freeze frame data, looking for other cylinder or sensor supply codes
  2. Inspect the cylinder 8 sensor connector and harness for chafing, moisture, heat damage or corrosion
  3. Check reference voltage, ground and signal wire with a multimeter per the factory wiring diagram
  4. Test the wires to the ECM for opens and shorts to ground or voltage
  5. Compare the sensor's live data with the other cylinders
  6. If wiring is good, swap in a known good sensor and see if the code clears
  7. Only then suspect the ECM and check for software updates

Common fixes

  • Replace the cylinder 8 pressure sensor
  • Repair the wiring harness or replace a damaged connector
  • Clean the terminals and restore sensor power and ground
  • Update or replace the ECM if everything else checks out

Questions and answers

What does P03DB mean?

The ECM sees a fault in the cylinder 8 pressure sensor circuit, with a missing or implausible signal. The sensor or its wiring is the most common cause.

Can I drive with P03DB?

Briefly and gently, for example to a shop, usually yes. If the engine shakes, misfires or loses power, stop driving.

Should I replace the sensor right away?

No. Check the connector, wiring, supply voltage and ground first, since these often cause the code rather than the sensor itself.

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.