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P3421 Generic (SAE) Basic entry

Cylinder 3 Exhaust Valve Control Circuit/Open

Updated 2026-10-02 · Ignition & auxiliary (P3)

Severity
Medium
Typical repair cost
40 – 350 EUR
System
Powertrain

What it means

P3421 means the engine control module cannot detect current flow in the Cylinder 3 Exhaust Valve Control Circuit circuit: the circuit is electrically open somewhere between the module, the connector and the component.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

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Symptoms

  • Check engine light on
  • Rough or unstable idle
  • Hesitation or poor acceleration
  • Increased fuel consumption
  • Possible limp mode with reduced power

Common causes

  1. Damaged, chafed or corroded wiring in the Cylinder 3 Exhaust Valve Control Circuit circuit
  2. Corroded, loose or water-damaged connector terminals
  3. Failed Cylinder 3 Exhaust Valve Control Circuit component (sensor, solenoid or actuator)
  4. Poor ground connection for the module or component
  5. Faulty control module driver (rare, confirm all else first)

How to diagnose

  1. Read freeze frame data and note when the code set (cold start, under load, after rain)
  2. Inspect the Cylinder 3 Exhaust Valve Control Circuit connector for bent pins, corrosion and water; wiggle the harness with the engine running and watch live data
  3. Measure supply voltage and ground at the connector with the key on
  4. Check the signal wire for shorts to ground or battery and for continuity to the control module
  5. Test or substitute the Cylinder 3 Exhaust Valve Control Circuit only after wiring and connectors are confirmed good
  6. Clear the code and complete a drive cycle to confirm the repair

Frequently asked questions

Can I keep driving with P3421?

Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.

Will clearing P3421 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.

Related codes

P3419P3420P3422P3423

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