P03DE: Cylinder 8 Pressure Sensor Circuit High

What it means

Cylinder 8 pressure sensor above upper plausibility — open signal or short to B+. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The cylinder 8 pressure sensor reports combustion pressure to the engine control module (ECM). The ECM monitors its signal against an upper plausibility limit; an open signal path or a short to battery voltage can make the reading appear too high and set this code.

Common causes

Most likely first.

1. Open signal line
2. Connector pins corroded - high contact resistance
3. Supply wire pinched against B+ source

Symptoms

• Check engine light on
• Possible engine misfire or rough running
• Reduced engine power
• Poor fuel economy

How to diagnose it

1. Record freeze-frame data and watch cylinder 8 pressure sensor data while the fault is present to see whether the reading is fixed high or implausible.
2. Inspect the cylinder 8 sensor connector and nearby harness for water, corrosion, chafing, loose fit, or a pushed-back pin.
3. With the wiring diagram, check the cylinder 8 sensor signal wire for an open circuit and for an unintended connection to battery positive.
4. Check the sensor supply and ground connections against the manufacturer's specification, including voltage drop across suspect connector contacts.
5. If the wiring and connections pass, test the cylinder 8 pressure sensor and ECM circuit according to the manufacturer's procedure.

Common fixes

• Clean and securely reconnect a contaminated or loose cylinder 8 pressure sensor connector.
• Repair chafed or open cylinder 8 sensor wiring and restore correct routing away from hot or moving parts.
• Repair a signal wire short to battery positive or replace a damaged connector terminal.
• Replace the cylinder 8 pressure sensor if it fails the manufacturer's test.

Can I keep driving?

If the engine runs smoothly, limit driving to a short trip for diagnosis and avoid heavy acceleration or loads. Misfire or rough running can worsen and increase emissions; stop if the engine begins misfiring badly or loses power.