P3403 code meaning
Cylinder 1 Deactivation/Intake Valve Control Circuit Low
Powertrain system Generic code P34xx codes Check engine light
What P3403 means
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.
P3403 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P3403
- Check engine lamp on after two trips
- Engine no longer switches to reduced-cylinder mode
- Somewhat higher fuel consumption
Common causes of P3403
- Most likelyControl wire chafed against the engine and shorted to ground
- PossibleInternal short in the cylinder 1 deactivation solenoid
- Less likelyOil or water in the solenoid connector
- Less likelyFaulty output driver in the engine control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cylinder deactivation solenoidWiring harnessECM
What each part of P3403 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 3 | Mixed range: generic and manufacturer-specific codes. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 03 | The exact fault in that area. |
What to do next
- Note P3403 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P3403
What does P3403 mean?
P3403 means "Cylinder 1 Deactivation/Intake Valve Control Circuit Low". The engine computer drives the deactivation valve for cylinder 1 through an output stage that checks its own wiring. It is a generic code, so it means the same on every make.
Is it safe to drive with P3403?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P3403 fail an emissions test?
Yes, it can. P3403 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P3403 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P3403 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.