John Deere 168.01 – PTQ: Control Software, Supply Voltage (BAT) Too Low

Triggered when the supply voltage to the control module drops below 9 volts. This is a severe level alert indicating a weak battery, a failing alternator, or a significant wiring fault preventing adequate power from reaching the module. When this error is detected, the control software functionality becomes limited or nonexistent, and the transmission may automatically shift to neutral or park to prevent damage.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6090MC
• 6090RC
• 6100MC
• 6100RC
• 6110MC
• 6110RC
• 7185J
• 7195J
• 7205J
• 7210J
• 7225J

1. 1

   Test the battery with a multimeter to ensure it holds an adequate charge (~12.6V resting) and does not drop below 9V under load

2. 2

   Test the alternator output while the engine is running to ensure it is properly charging the system

3. 3

   Check the fuses supplying power to the transmission and rear chassis control units (e.g., F9 or F23)

4. 4

   Inspect the wiring harness leading to the PTQ (Rear Chassis Module) for chafed wires, loose ground connections, or corrosion at the battery terminals and module connectors

1. 1

   Secure the Machine

   Park the tractor on a level surface, engage the parking brake, and turn off the engine.

2. 2

   Clean and Tighten Terminals

   Remove the battery cables (negative first). Clean the battery posts and cable terminals with a wire brush to remove any corrosion. Reinstall and tighten securely.

3. 3

   Test/Replace the Battery

   If the battery fails a load test or cannot maintain voltage above 9V, replace it with a new heavy-duty agricultural battery.

4. 4

   Test/Replace the Alternator

   If the battery is good but the system voltage drops while running, replace the alternator.

5. 5

   Inspect the PTQ Harness

   Locate the Rear Chassis Module (PTQ). Disconnect its main harness connector and inspect the pins for corrosion, moisture, or pushed-back pins. Clean with electrical contact cleaner if necessary.

6. 6

   Clear Codes

   After restoring proper voltage (above 9V), cycle the key switch. The PTQ 168.01 code is typically recoverable and will clear once normal operating voltage is detected.

7. 7

   Module Replacement (Worst Case)

   If the battery, alternator, and wiring all test perfectly (delivering 12V+ to the module connector) but the code persists, the PTQ module itself has an internal power supply failure and must be replaced and reprogrammed by a John Deere dealer.