Fuel Injector Group Supply Voltage Circuit Low
The P2156 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the supply circuit for a group of fuel injectors. This circuit provides the necessary voltage for injector operation. A low voltage can cause injectors to malfunction, leading to poor engine performance, misfires, or stalling. The issue may stem from a faulty injector driver, damaged wiring, poor electrical connections, or a failing PCM.
1. Most Common Causes
- Faulty fuel pump relay or injector relay with excessive contact resistance
- Blown or incorrect amperage fuse in the group D power supply circuit
- Loose connection, corrosion, or excessive resistance at the injector harness connector
- Short to ground in the power supply circuit wiring
- Open or intermittent circuit in the voltage supply to group D
- Internal ECM/PCM failure in the injector control or supply circuit
- Faulty injector control module (ICM), if applicable
2. Symptoms You Will Notice
- Engine misfire or rough idle
- Check Engine Light illuminated
- Poor fuel economy
- Engine hesitation or stalling
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P2156 and check for other codes.
Step 2: Visually inspect injector wiring and connectors for damage or corrosion.
Step 3: Test voltage at injector supply circuit with a multimeter (should be near battery voltage).
Step 4: Check fuses and relays related to injector power.
Step 5: If wiring and fuses are okay, test injector driver module or PCM output.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Low voltage to injectors can cause engine misfires, poor performance, and potential damage to the catalytic converter. Have it diagnosed promptly.
How much does it cost to fix?▼
Repair costs vary: simple wiring repairs $150-$250, injector driver module $200-$400, PCM replacement $500-$1000. Diagnosis fee typically $100-$150.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.