Code Severity and Symptoms
The severity of this code is moderate but will progress if not corrected in a timely manner. Symptoms of a P2628 fault code may include:
- Worsening poor performance
- Engine running lean
- Engine running rich
- Check engine light illuminated
- Smoke from the exhaust pipe
- Increased fuel consumption
Common Causes of P2628 Code
Possible causes of this code may include:
- Faulty O2 sensor
- Carbon buildup on the O2 sensor
- Blown fuse (if applicable)
- Fuel pressure too high
- Fuel pressure too low
- Engine vacuum leak
- Excessive exhaust leak
- Corroded or damaged connector
- Faulty or damaged wiring
- Faulty PCM
Common Repairs
- Replacement or cleaning of the O2 sensor
- Replacement of blown fuse (if applicable)
- Adjusting fuel pressure
- Repairing engine vacuum leaks
- Repairing exhaust leaks
- Cleaning connector corrosion
- Repairing or replacing wiring
- PCM replacement
P2628 Diagnostic and Repair Procedures
Check TSBs
The first step in troubleshooting any malfunction is to search for Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and powertrain. In some circumstances, this can save significant time in the long run by pointing you in the right direction.
The second step is to locate the pre-catalytic converter O2 sensor. Perform a thorough visual inspection to check the associated wiring for obvious defects such as scraping, rubbing, bare wires, or burns. Then, check the connector for security, corrosion, and damaged pins. With the engine running, the visual inspection should include identifying possible exhaust leaks. Based on fuel consumption and fuel pressure tests, engine operation adjustments may be recommended. You should consult specific technical data to determine this requirement.
Advanced Steps
Advanced steps become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and vehicle-specific technical references. Voltage requirements will be highly dependent on the specific vehicle year, model, and engine.
Voltage Checks
When the fuel mixture is balanced at approximately 14.7:1, which is normal for most engines to achieve optimal performance, the sensor will read about 0.45 volts. An oxygen sensor typically generates up to about 0.9 volts when the fuel mixture is rich and there is unburned oxygen in the exhaust gases. When the mixture is lean, the sensor’s output voltage will drop to about 0.1 volts.
If this process identifies the absence of a power source or ground, continuity tests may be required to check wiring integrity. Continuity tests should always be performed with the power disconnected from the circuit, and normal readings should be 0 ohms of resistance unless otherwise indicated by technical data. Resistance or lack of continuity indicates faulty open or shorted wiring and should be repaired or replaced.
I hope the information in this article has helped point you in the right direction to correct the issue with your O2 sensor pump current compensation circuit. This article is strictly informational, and specific technical data and service bulletins for your vehicle should always take priority.