Common Symptoms
- Check Engine Light illuminated
- Rough idle or engine misfire on cold start
- Reduced engine power and acceleration
- Engine runs rough under load
- Increased fuel consumption
- Black smoke from exhaust
Most Likely Root Causes
- Faulty fuel injector on cylinder 1
- Damaged or shorted wiring harness to cylinder 1 injector
- Corroded or loose injector connector
- Failed fuel injector driver circuit in PCM
- Chafed wiring causing short to ground
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Component Location
Cylinder 1 fuel injector is located in the cylinder head on the number one cylinder, typically the front-most cylinder on inline engines or driver side front on V-engines.
Manufacturer Notes
Some manufacturers use individual injector driver modules rather than PCM-integrated drivers which can be separately diagnosed and replaced.
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Heavy-duty trucks often throw both OBD-II and J1939 faults simultaneously. AI Diesel Tech handles both protocols in a single guided session.
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