John Deere 158.16 – HV1: High Voltage Detected On HV1 Hydraulic Control Module

The control module is receiving a supply voltage that exceeds the maximum allowable threshold for the 12-volt system (typically anything over 15.0V - 15.5V). This is almost always a symptom of an overcharging alternator due to a failed voltage regulator.

• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 5115ML
• 4930 Sprayer
• 210LJ Landscape Loader
• 644H Loader

1. 1

   Perform a static battery test with the engine off using a digital multimeter (should read 12.4V to 12.8V)

2. 2

   Perform a running voltage test at fast idle to check alternator output (readings above 14.8V - 15.5V indicate a failed voltage regulator overcharging the system)

3. 3

   Inspect main ground cables (chassis, cab harness, and starter motor) for looseness or heavy corrosion

4. 4

   If alternator output is normal (13.5V-14.5V), back-probe the unswitched battery power connector at the HV1 module to verify actual voltage reaching the pins

1. 1

   Disconnect Power

   Turn off the key switch and disconnect the negative battery cable to prevent electrical arcing.

2. 2

   Clean Grounds

   Remove, wire-brush, and re-secure the main chassis and cab grounds.

3. 3

   Replace the Alternator

   If the running voltage test confirmed an overcharge condition, the internal voltage regulator is faulty. Remove the serpentine belt, disconnect the alternator excitation and B+ wires, and unbolt the alternator.

4. 4

   Install New Alternator

   Mount the replacement alternator, torque the mounting bolts to OEM spec, reconnect the wiring harness, and reinstall the drive belt (ensure proper tension).

5. 5

   Re-test System

   Reconnect the battery, start the tractor, and verify that the running voltage is now stabilized between 13.5V and 14.5V.

6. 6

   Clear Codes

   Use a John Deere Service ADVISOR tool (or the onboard diagnostic dash menu) to clear the 000158.16 historical code.