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. This can lead to improper fuel dosing, affecting emissions and potentially causing damage to aftertreatment components.
1. Most Common Causes
- Short to power in the injector control circuit
- Faulty exhaust aftertreatment fuel injector
- Damaged wiring or connectors in the injector circuit
- Failed PCM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced fuel economy
- Increased exhaust emissions
- Possible DPF regeneration issues or frequent regeneration cycles
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the wiring and connectors for damage, corrosion, or loose connections.
Step 3: Test the injector resistance with a multimeter and compare to manufacturer specifications.
Step 4: Check for voltage at the injector connector with the key on; if voltage is present when it shouldn't be, trace the short to power.
Step 5: If wiring and injector are okay, test the PCM output circuit for proper operation.
4. 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 improper exhaust aftertreatment operation, increased emissions, and potential damage to the DPF or SCR system. You may notice reduced performance and fuel economy.
How much does it cost to fix?▼
The cost to fix P20D4 typically ranges from $150 to $400, depending on the cause. Replacing the injector can cost $100-$250 for parts plus labor, while wiring repairs are usually less expensive.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.