P0203
Injector Circuit/Open - Cylinder 3
When a vehicle powertrain module registers the fault code P0203, it points directly to an internal system malfunction identified as "Injector Circuit/Open - Cylinder 3". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
Your vehicle's computer logged P0203 after detecting a malfunction in the injector circuit/open - cylinder 3 system. Typical symptoms include stalling, rough acceleration, flashing check engine light. Stop driving as soon as it is safe to do so. This fault can lead to expensive secondary damage if left unaddressed.
Symptoms
Stalling, rough acceleration, flashing check engine light
Common Causes
- Bad fuel injector on Cylinder 3
- Rodent damage to injector wiring
- Loose electrical connection
- Blown injector fuse
How to Fix
- 1 Swap or replace fuel injector
- 2 Splice and repair damaged wiring
- 3 Check connection tightness
- 4 Check fuses
Technical Explanation
Code P0203 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
An active P0203 code under high-severity conditions means the affected system is operating outside safe parameters. Continued driving — especially under load or at highway speeds — significantly increases the risk of secondary damage to components like rodent damage to injector wiring.
Mechanic's Pro Tip
When diagnosing P0203, always test fuel volume delivery in addition to static pressure — a pump that holds pressure at idle but delivers insufficient volume under load will cause the fault only during acceleration or high demand, making it difficult to replicate in the driveway. Use a fuel pressure gauge with a volume outlet port: a healthy pump should deliver at least 1 liter per minute. Replace the fuel filter first; it's the cheapest test and solves the fault in a significant percentage of cases.
Wiring repair: $100; Injector: $150 - $400