John Deere 94.17 – ECU: Low Pressure Fuel Sensor Voltage Low / Fuel Pressure Low / Fuel Rail Pressure Not Developed

The controller has detected that the voltage signal from the low-pressure fuel sensor is slightly below the expected specification. This under-voltage indicates that there is insufficient fuel delivery pressure coming out of the lift pump (transfer pump), or that the required rail pressure is not being developed within a few seconds of engine cranking.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5065M
• 5075M
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5095M
• 5095MH
• 5105M
• 5015ML
• 5090M
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 5E Series
• 6R Series
• 7000 Series
• 8000 Series
• 7820
• 8430
• 8530
• 9570
• 9660 STS
• 9760 STS
• S-Series
• 7760
• 748H Skidders
• 310-Series Backhoes
• Articulated Dump Trucks
• 6M Series
• 7420
• 7810
• 8120

1. 1

   Ensure there is adequate fuel in the tank and check for water, algae, or debris.

2. 2

   Inspect all fuel lines and fittings between the tank and the lift pump for air leaks, checking for loose fittings or poor filter gaskets.

3. 3

   Check the fuel tank suction pipe and screen for partial blockages or plastic flashing.

4. 4

   Install a mechanical pressure gauge in-line with the output of the low-pressure fuel transfer pump and rev the engine to check for pressure drops.

5. 5

   Inspect the low-pressure fuel sensor connector and wiring harness for damage, corrosion, or loose pins, and check the 5V reference circuit for a short or open circuit.

6. 6

   If the engine cranks but won't start after sitting, check for fuel drain-back issues caused by a clogged check valve, failed high-pressure pump overflow valve, or stuck-open final fuel filter relief valve.

1. 1

   Drain and Clean

   Drain the fuel filters and water separator. If heavy contamination is found, drain and flush the fuel tank and blow out the fuel lines with compressed air.

2. 2

   Replace Filters

   Change both the primary and secondary fuel filters. Ensure the filter gaskets are seated correctly to prevent air intrusion.

3. 3

   Clean the Suction Screen

   Remove the fitting on top of the fuel tank, pull out the suction pipe, and clean the attached suction screen.

4. 4

   Bleed the System

   Use the hand primer to bleed the fuel system completely until a firm, airless stream of fuel is achieved.

5. 5

   Clean Sensor Contacts

   Spray the low-pressure fuel sensor electrical connector with electronic contact cleaner and reconnect it securely.

6. 6

   Test Run

   Clear the codes and run the machine under load.

7. 7

   Replace Components

   If the code returns and mechanical pressure is verified to be low, replace the fuel transfer pump (lift pump). If mechanical pressure is perfectly within spec but the ECU still reads low voltage, replace the low-pressure fuel sensor.