Code result
P034C
Ion Sense System Performance
High severity
What it means
Some engines (notably Saab and some Mazda direct-injection units) use the spark plug as an ion-current sensor after spark to detect knock and misfire. This code reports a performance issue with the ion-sense input — typically a worn plug, loose secondary connection, or aged ion-sense module.
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
Spark plugs worn
highOne of the most commonly reported causes for this code — check this first.
Ion-sense module aged
mediumA plausible cause — test and verify before replacing parts.
Related help
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