What Does P20D4 Mean?
The PCM has detected voltage in the exhaust aftertreatment fuel injector B control circuit that is above the expected range. This indicates a short to power or open ground circuit.
Common Causes
35%
Short to voltage in injector B wiring harness or connector
30%
Open ground circuit for injector B preventing current flow
20%
Damaged wiring making contact with power source or another powered circuit
10%
PCM internal driver circuit failure holding voltage high
5%
Faulty exhaust fuel injector B with internal open circuit
Diagnostic Steps
1
Step 1: Disconnect injector B and measure voltage at harness connector with key on (should be 0V on control wire)
2
Step 2: Verify ground circuit continuity from injector B to PCM and to chassis ground
3
Step 3: Inspect wiring for damage or contact with other circuits, especially near heat sources
4
Step 4: Check for proper PCM ground connections and verify no voltage drop across ground circuits
5
Step 5: Monitor control circuit voltage with oscilloscope during commanded injector operation
Estimated Repair Cost
$150 - $1,300
Parts + labor, varies by vehicle and location
The PCM has detected voltage in the exhaust aftertreatment fuel injector B control circuit that is above the expected range. This indicates a short to power or open ground circuit.
The most common cause of P20D4 (Exhaust Aftertreatment Fuel Injector "B" Control Circuit High) is: Short to voltage in injector B wiring harness or connector
Typical repair costs for P20D4 range from $150 to $1,300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle remains drivable but regeneration capability is compromised, which may lead to DPF issues and eventual engine derate. No immediate safety risk.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20D4 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
Exhaust Aftertreatment System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
