P0203: Cylinder 3 Injector A Circuit
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Short trips only.
Symptoms
- Cylinder 3 misfire
- Shaking at idle
- Flashing check engine light under load
Likely causes, most common first
- Injector 3 circuit fault
- Rodent damage to the harness
- Oil-soaked connector
- Broken wire at the harness bend
Read P0203 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0203 - injector 3's circuit. Injector harnesses run along the fuel rail on top of the engine, warm and sheltered, which makes them a favorite of rodents; chewed injector wiring is a genuinely common cause of single-injector codes appearing overnight on a car that was fine yesterday.
The visual check costs nothing: pull the engine cover and look along the rail for insulation damage and for connectors sitting proud of their injectors. A connector that did not click home after previous work announces itself this way weeks later, once vibration finishes the job.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0203
“Seat belt light on. Car went into limp mode while on the highway. Seat belt acted like it was loose. Went for scan and it pulled up diagnostic code P0203 which is Replace Fuel injector wiring harness. Saying Cylinder 3 circuit malfunction. Also threw code P050B.”2018 Volkswagen Tiguan · May 2025
“At 62,000 miles transmission had to be replaced at my expense now at 75,000miles misfire on cylinder 3 code p0203 still waiting to be fixed then over heat warning light would come on and then go off while driving”2018 Ford Escape · May 2020
Cars that report P0203 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0203?
Short trips only.
How much does it cost to fix P0203?
Typical US repair costs range from $60 for the simplest fix (wiring repair) to $600 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0203. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.