P3403: Cylinder 1 Deactivation/Intake Valve Control Circuit Low
Standardized SAE J2012 code · P34xx codes
What does P3403 mean?
The engine computer drives the deactivation valve for cylinder 1 through an output stage that checks its own wiring. P3403 means that check found the control line pulled to ground. GM documents it for the L84 and L86 V8s (2019): with the driver off, an impedance below 0.5 ohm to ground counts as a fault, and 20 failures in 25 samples taken every 250 ms set a Type B code, so the lamp comes on after the second trip. Ford's VDE monitor flags the same short via its smart driver within 5 seconds. An open line is P3401, a short to battery voltage P3404, a mechanical failure P3402. The engine then stays in all-cylinder mode, mainly costing fuel.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Check engine lamp on after two trips
- Engine no longer switches to reduced-cylinder mode
- Somewhat higher fuel consumption
Common causes
- High Control wire chafed against the engine and shorted to ground
- Medium Internal short in the cylinder 1 deactivation solenoid
- Low Oil or water in the solenoid connector
- Low Faulty output driver in the engine control module
Likelihood is a general estimate across vehicles; your make and model may differ.
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