What is the P0294 Code?
The P0294 error code is a generic powertrain (OBD-II) code that indicates a low voltage circuit problem at cylinder 12’s fuel injector. The engine control module (PCM) detected an abnormally low voltage in this injector’s electrical circuit.
A faulty injector can cause a cascade of problems: it creates a lean air-fuel mixture in its cylinder, which the oxygen sensor detects. The PCM then compensates by enriching the mixture for all cylinders, causing fuel economy to drop. Cylinder 12, operating with a lean mixture, can overheat and lead to engine knocking (detonation). The PCM responds by retarding the ignition timing, resulting in poor performance, power loss, and premature engine wear.
Symptoms of the P0294 Code
- 📈 Check Engine Light illuminated
- ⚡ Rough running or shaking engine
- 🔻 Noticeable power loss during acceleration
- ⛽ Significant increase in fuel consumption
- 💥 Knocking or detonation noises from the engine
Possible Causes of the Fault
- 🔌 Loose, corroded, or damaged electrical connector on injector #12
- 🛠️ Clogged, blocked, or defective fuel injector
- 🔋 Electrical circuit problem: cut wire, short circuit, or poor connection
- 💥 Malfunctioning injector driver in the PCM (less common)
Diagnosis and Repair Procedure
Step 1: Visual Inspection
Locate cylinder 12’s injector. Inspect its electrical connector. Ensure it is properly seated, and check for any signs of corrosion, damage, or pushed-back pins.
Step 2: Basic Electrical Test
– Disconnect the injector connector.
– Using a multimeter, check for power supply current (typically 12V) at the corresponding terminal when the ignition is on. No voltage? Check the fuel pump fuse and relay.
– If the power supply is good, test the ground circuit controlled by the PCM. The multimeter should display rapid pulses when the engine is idling.
Step 3: Injector Test
– Use a mechanical stethoscope to listen for the characteristic “click” of the injector while the engine is running. Its absence indicates a problem.
– You can also measure the injector’s (coil) resistance using a multimeter and compare the value with other injectors or manufacturer specifications.
Step 4: Cleaning or Replacement
– If the injector is dirty, use a direct injector cleaning kit. This simple and inexpensive operation may solve the problem.
– If the injector is electrically defective or severely clogged, replacement is necessary. It is often recommended to replace injectors in batches to avoid imbalances.
⚠️ Safety Tip
Before any work, turn off the ignition and disconnect the battery. Injector circuits are live. If you are not comfortable with these procedures, consult a professional mechanic for an accurate diagnosis.
Need help diagnosing or finding the right part? Consult our complete fault code guide or contact our community of mechanical experts for personalized advice.