Exhaust Aftertreatment Fuel Injector Circuit Open (Generic)
The P4056 code means the vehicle's onboard diagnostic system has detected: Exhaust Aftertreatment Fuel Injector Circuit Open (Generic). This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- hard
- Estimated cost
- $200 - $600 (parts and labor)
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Common Symptoms
- Check Engine Light on
- DPF regeneration will not activate
- Soot loading increasing rapidly
- Service exhaust system warning
- Reduced engine power
Probable Causes (Ranked by Likelihood)
- Open circuit in aftertreatment injector wiring Very High
- Failed aftertreatment fuel injector High
- Damaged connector from heat Moderate
- PCM driver circuit failure Low
Step-by-Step Diagnostic Procedure
-
Check injector connector and wiring continuity
-
Measure injector solenoid resistance
-
Verify PCM driver output signal
-
Inspect injector for heat damage or carbon buildup
Frequently Asked Questions
What is an aftertreatment fuel injector?
It injects fuel into the exhaust stream upstream of the DPF to raise exhaust temperatures high enough for soot regeneration.
Can I drive with P4056?
No, without DPF regeneration capability, soot will accumulate rapidly and can clog the DPF within a few hundred miles.
How much does the aftertreatment injector cost?
The injector costs $100-300. With labor, expect $250-600 total.
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