P0204
UniversalInjector Circuit Malfunction - Cylinder 4
The engine computer has detected an electrical problem in the fuel-injector circuit for cylinder 4. The injector controls fuel delivery to that cylinder. A circuit fault can disrupt fueling and cause rough running, reduced power, or increased emissions, but the code alone does not prove the injector itself has failed.
⚠️ Before You Begin (Safety First)
If the engine runs very roughly, loses significant power, or the check-engine light flashes, stop driving when it is safe to do so and arrange an inspection; continued operation may risk further damage. If you smell or see fuel, shut the engine off and keep away from ignition sources. Do not disconnect or test wiring with the engine running.
Common Symptoms
- The check-engine light may be on, with or without noticeable drivability problems.
- Rough idle or engine vibration may occur if cylinder 4 is not fueled correctly.
- Misfiring, hesitation, or reduced power may occur when accelerating.
- Fuel economy or emissions may worsen if the circuit fault disrupts combustion.
- The vehicle may have no obvious symptoms if the fault is intermittent or has limited effect on engine operation.
Common Causes
- A loose, damaged, corroded, or contaminated connection at the cylinder 4 injector.
- Damaged wiring, such as a break, short, or poor connection in the injector circuit.
- An electrical fault within the cylinder 4 injector; the code does not by itself confirm injector failure.
- A problem with circuit power, ground, or the engine computer's injector control driver.
Diagnostic Steps
- Record the code and any available freeze-frame information before clearing codes; this can help show when the fault was detected.
- With the engine off and cool, visually inspect the cylinder 4 injector connector and accessible harness for looseness, corrosion, chafing, or damage. Do not pull on wires or force a connector.
- Check for related codes and note whether the engine runs roughly or loses power; these clues can help a technician narrow down the fault.
- Avoid probing computer terminals, applying power to injector wiring, or replacing parts based only on the code. Have circuit testing performed using vehicle-specific service information if the visual checks do not reveal an obvious issue.
When to Call a Professional
A technician can inspect the cylinder 4 injector connector and harness, review scan data, and test the injector circuit using the vehicle-specific wiring diagram and service procedure. Comparing circuit behavior with other cylinders can help distinguish a wiring or connection fault from an injector or control-driver problem. Confirm the fault before replacing parts.
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Commonly Asked Questions
Does P0204 mean the cylinder 4 injector must be replaced?
No. The code identifies a detected injector-circuit malfunction, not a confirmed failed injector. The connector, wiring, circuit supply or control driver may also need investigation.
Is an injector circuit problem the same as a cylinder misfire?
No. P0204 identifies an electrical circuit condition for cylinder 4. A misfire may result if fueling is disrupted, but a misfire code describes a different detected condition.
Can I keep driving with P0204?
It depends on how the vehicle runs. Avoid driving if the engine is shaking severely, power is substantially reduced, the check-engine light is flashing, or fuel is leaking or smells strong.
Can a visual inspection find the cause?
Sometimes. A loose connector or visibly damaged harness may be apparent, but many electrical faults require circuit testing with the vehicle-specific wiring diagram and service information.
Browse Available Code Guides
Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.