Code result
P039E
Cylinder 1 Combustion Performance
High severity
What it means
The closed-loop combustion controller reports that combustion performance on cylinder 1 is below the calibrated quality metric. Computed from the cylinder pressure trace — IMEP (indicated mean effective pressure), CA50 (50% mass burnt angle) or peak pressure deviates from the model.
Is it safe to drive?
No — stop driving
This code points to a problem that can cause damage or affect safety. Avoid driving and have the vehicle diagnosed promptly.
Most likely causes
Injector flow rate drift
highOne of the most commonly reported causes for this code — check this first.
Low compression
mediumA plausible cause — test and verify before replacing parts.
Gateway module routing CAN messages incorrectly
lowLess common, but worth ruling out after the more likely causes.
Related help
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