John Deere 000158.03 – SFA: High Ignition Supply

The Suspended Front Axle (SFA) control module has detected that its ignition supply voltage is excessively high (typically above 18 volts). This abnormal voltage level indicates either a systemic overcharging issue, such as a defective alternator, or an isolated fault within the SFA controller or its wiring circuit. This condition often results in limited or non-functional control software for the affected module.

• 6020 to 6920S Series
• 7720, 7820, and 7920 Tractors
• 8130 to 8530 and 8230T to 8430T Series
• 8R and 8RT Series
• 9230 to 9630 Series

1. 1

   Restart the engine to perform an initial system reset and see if the code clears

2. 2

   Check for other diagnostic trouble codes to see if multiple control units (e.g., CAB, ITC, ASU, AIC) are reporting high voltage, which strongly suggests a systemic charging issue

3. 3

   Visually inspect the electrical system around the batteries and alternator for damage, corrosion, or debris, ensuring cables are secure and clean

4. 4

   With the engine running, check the system voltage to ensure it does not exceed 18 volts

5. 5

   Inspect fuse F30 (for SFA-specific voltage issues) and fuse F15 (if CAB-related issues are present)

1. 1

   Confirm the fault

   Record and clear the fault code, then operate the tractor to see if SFA 000158.03 returns. If intermittent, continue operation until it reappears to confirm it is an active issue.

2. 2

   Test and replace alternator (Systemic Cause)

   If multiple control units are logging a 'voltage high' error, the primary suspect is the alternator. Test the alternator's output to confirm it is overcharging the system (above 18 volts). If defective, replace the alternator.

3. 3

   Test SFA power and ground (Isolated Cause)

   If only the SFA module is logging the 000158.03 code, the issue is likely isolated to the SFA controller or its wiring. Test the power supply and ground circuit for the SFA control unit, checking for continuity and ensuring there are no shorts or high resistance in the wiring harness.

4. 4

   Replace SFA Control Unit

   If the wiring and charging system are confirmed to be in good working order, the SFA control unit itself is likely faulty. Replace the SFA module. Note that a new control unit may require programming by a John Deere dealer.