John Deere 158.18 – HV1 (Hydraulic Control Module 1): Switched Supply Voltage Low

Triggers when the supply voltage to a control module drops below the normal operating range (typically below 11.0V or 11.2V) while the engine is running at low to mid-range speeds (usually between 500 and 1500 RPM).

• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 5115ML

1. 1

   Battery Test: Check the battery's state of charge and perform a heavy load test to ensure it can maintain voltage.

2. 2

   Charging System Test: Check the alternator output voltage with the engine running between 500 and 1500 RPM. The system should be producing between 13.5V and 14.5V.

3. 3

   Visual Inspection of Connections: Inspect the battery terminals, alternator connections, and main chassis ground straps for corrosion, looseness, or accumulated debris.

4. 4

   Harness Check: Trace the switched power circuit wiring harness supplying the HV1 Hydraulic Control Module. Look for chafing, shorts to ground, or high resistance in the connectors.

1. 1

   Clean Connections

   Disconnect the battery and thoroughly clean the battery posts, terminals, and main ground connections. Reconnect and tighten them securely.

2. 2

   Replace Battery

   If the battery fails the load test or cannot hold a charge above 12V when the machine is off, replace it.

3. 3

   Replace Alternator

   If the battery is good but the alternator fails to maintain at least 13.5V while the engine is running at 1500 RPM, replace the alternator.

4. 4

   Repair Wiring

   If the battery and alternator are functioning perfectly, use a multimeter to check the voltage drop at the HV1 module connector. Repair or replace any damaged wiring or corroded pins in the harness supplying the module.

5. 5

   Clear and Verify

   Clear the fault codes from the system. Start the engine, operate the tractor at mid-range RPM (500-1500 RPM), and engage the hydraulics to verify the code does not return.