What Does P20CB Mean?
The powertrain control module has detected an open circuit or lack of continuity in the control circuit for the exhaust aftertreatment fuel injector (hydrocarbon doser). This injector sprays fuel into the exhaust to aid regeneration of the diesel particulate filter or support SCR catalyst heating.
Common Causes
30%
Broken or severed wiring in injector control circuit
25%
Failed exhaust fuel injector with internal open circuit
20%
Corroded or disconnected electrical connector at injector
15%
Damaged PCM/ECM driver circuit for injector control
10%
Blown fuse or open relay in injector power supply circuit
Diagnostic Steps
1
Step 1: Inspect exhaust fuel injector connector for corrosion, damage, or loose connection and clean/repair as needed
2
Step 2: Measure resistance across injector coil terminals and compare to specifications (typically 2-10 ohms)
3
Step 3: Check for battery voltage at injector connector with key on, engine off
4
Step 4: Backprobe injector connector and check for ground signal from PCM during commanded injection event
5
Step 5: Inspect wiring harness from injector to PCM for chafing, breaks, or damage, paying attention to high-heat areas near exhaust
Estimated Repair Cost
$150 - $1,500
Parts + labor, varies by vehicle and location
The powertrain control module has detected an open circuit or lack of continuity in the control circuit for the exhaust aftertreatment fuel injector (hydrocarbon doser). This injector sprays fuel into the exhaust to aid regeneration of the diesel particulate filter or support SCR catalyst heating.
The most common cause of P20CB (Exhaust Aftertreatment Fuel Injector "A" Control Circuit/Open) is: Broken or severed wiring in injector control circuit
Typical repair costs for P20CB range from $150 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive short-term but DPF regeneration will fail, leading to restricted exhaust flow and potential engine derate. Address promptly to avoid DPF damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20CB to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Emissions Control - Diesel Particulate Filter Regeneration
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
