Exhaust Aftertreatment Fuel Injector Control Circuit High
The P20D4 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the control circuit of the exhaust aftertreatment fuel injector. This injector is used in diesel engines to introduce fuel into the exhaust stream for regeneration of the diesel particulate filter (DPF) or to raise exhaust temperature for selective catalytic reduction (SCR) systems. A high voltage reading typically points to a short to power, a faulty injector, or a wiring issue.
01. Most Common Causes
- Short to power in the injector control circuit
- Faulty exhaust aftertreatment fuel injector
- Damaged wiring or connectors
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced fuel economy
- Possible DPF regeneration issues
- Excessive exhaust smoke
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all codes and freeze frame data.
Step 2: Visually inspect the injector wiring and connectors for damage, corrosion, or shorts.
Step 3: Test the injector resistance with a multimeter (compare to specs).
Step 4: Check for voltage at the injector connector with key on; should be battery voltage on one pin and ground on the other when commanded.
Step 5: If wiring and injector are okay, test the PCM output circuit for shorts or opens.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can lead to incomplete DPF regeneration, increased emissions, and potential damage to the exhaust system.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts and labor, depending on the cause and vehicle model.