What Does P20D9 Mean?
The PCM detects voltage on the aftertreatment fuel injector control circuit is lower than expected. This indicates an electrical problem preventing proper injector operation.
Common Causes
40%
Shorted to ground wiring in injector control circuit
30%
Failed aftertreatment fuel injector with internal short
20%
Corroded or damaged connector terminals
8%
Failed PCM driver circuit
2%
Chafed wiring harness rubbing on frame or exhaust
Diagnostic Steps
1
Step 1: Measure voltage and resistance at aftertreatment fuel injector connector with key on, engine off
2
Step 2: Inspect connector for bent pins, corrosion, or moisture intrusion
3
Step 3: Check for short to ground in wiring harness using resistance measurements
4
Step 4: Test injector coil resistance and compare to specifications
5
Step 5: Verify PCM driver circuit integrity by backprobing PCM connector
Estimated Repair Cost
$200 - $1,200
Parts + labor, varies by vehicle and location
The PCM detects voltage on the aftertreatment fuel injector control circuit is lower than expected. This indicates an electrical problem preventing proper injector operation.
The most common cause of P20D9 (Exhaust Aftertreatment Fuel Supply Control Circuit Low) is: Shorted to ground wiring in injector control circuit
Typical repair costs for P20D9 range from $200 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may operate with reduced power to protect emissions system. Continued operation without repair can damage DPF or catalyst components.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20D9 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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