The P1093 code on your 2020 Chevrolet Express indicates the fuel rail pressure is too low during engine cranking. This GM-specific code affects your Express's 6.6L Duramax diesel engine (on diesel models) or gasoline engine's ability to achieve adequate fuel pressure for starting, resulting in hard starting or no-start conditions.
Understanding P1093 on Express
Modern fuel injection systems require specific fuel rail pressure for proper injector operation. During cranking, the fuel system must quickly build and maintain pressure. Code P1093 sets when the PCM detects fuel rail pressure significantly below the required threshold during the cranking event, preventing proper fuel delivery for combustion.
Common Symptoms
- Check engine light on
- Extended cranking time
- Hard starting, especially when cold
- Engine may not start at all
- Engine stalls immediately after starting
- Loss of power if pressure drops while running
- Possible fuel system noise
Primary Causes
- Weak or failing fuel pump
- Clogged fuel filter
- Fuel pressure regulator failure
- Fuel system air leak (return line issues)
- Fuel injector leaking internally
- High-pressure fuel pump failure (diesel)
- Fuel supply restriction
- Low fuel level in tank
Diagnostic Procedure for 2020 Express
Connect fuel pressure gauge to the rail and observe pressure during cranking - compare to specification. Check fuel filter service history and replace if due. Perform fuel pump volume test to verify adequate delivery. On diesel models, check low-pressure supply pump and high-pressure injection pump separately. Inspect for air in fuel system. Test fuel pressure regulator operation. Check for leaking injectors by monitoring pressure decay with engine off.
Repair Solutions
Replace clogged fuel filter - this is the most common and simplest cause. If fuel pump pressure or volume is low, replace the fuel pump assembly. Repair any fuel system air leaks. Replace faulty fuel pressure regulator. On diesel models, injection pump replacement may be required for high-pressure failures. Ensure adequate fuel in tank. After repairs, bleed any air from fuel system and verify proper pressure during cranking.