P03A8 Cylinder 2 Combustion Performance

Some diesels have a combustion pressure sensor in the glow plug; the engine module uses it to control injection for each cylinder. This code concerns cylinder 2. P03A8 means the combustion quality in the cylinder, evaluated from the combustion pressure, is abnormal. No manufacturer document available to us describes the code; a GM patent shows the method: the ratio of measured to motoring pressure is turned into a measure of combustion energy, an inequality index against the neighbouring cylinders in firing order is formed, and a two-sided threshold detects partial combustion, misfire, injector and compression faults. CARB requires engines with a combustion or combustion quality sensor to detect misfire more sharply (5 % in 1,000 revolutions). Typical causes are a coked or leaking injector, compression loss or poor fuel; the engine runs roughly and smokes more.

Likely causes

Symptoms

• Check engine light on
• Rough running, vibration
• Loss of power, more smoke and consumption

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: patents.google.com, law.cornell.edu, borgwarner.com.