P20CB - Exhaust Aftertreatment Fuel Injector Control Circuit/Open
The P20CB code indicates an open or malfunction in the control circuit of the exhaust aftertreatment fuel injector, which is used in diesel engines to inject fuel into the exhaust stream for regeneration of the diesel particulate filter (DPF) or selective catalytic reduction (SCR) system. This circuit includes the injector itself, wiring, connectors, and the engine control module (ECM). An open circuit means there is a break in the electrical path, preventing the injector from operating. This can lead to incomplete regeneration, increased emissions, and potential damage to aftertreatment components.
01. Most Common Causes
- Faulty exhaust aftertreatment fuel injector
- Open or shorted wiring in the injector control circuit
- Corroded or damaged connectors
- Failed engine control module (ECM)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced fuel efficiency
- Increased exhaust emissions
- Possible DPF regeneration issues or frequent regeneration cycles
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for related codes.
Step 2: Visually inspect the injector, wiring, and connectors for damage, corrosion, or loose connections.
Step 3: Test the injector resistance with a multimeter (specs vary by vehicle; typically 0.5-2 ohms).
Step 4: Check for voltage and ground at the injector connector with the key on; if missing, trace circuit back to ECM.
Step 5: If wiring and injector are good, test ECM output or replace ECM as last resort.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can lead to DPF clogging, increased emissions, and potential engine damage. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
The cost typically ranges from $150 to $400, including parts and labor. The injector itself costs $50-$150, and labor is about $100-$250 depending on vehicle and shop rates.