John Deere 168 – PTA: Supply Power Valid but Above Normal Operational Range - Most Severe Level

The unswitched battery power supply to the controller has exceeded the maximum normal operating threshold (typically registering above 18 Volts). This is an overvoltage condition that can cause the system to disable transmission functions to protect the electronic circuits.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6M Series
• 6230
• 6330
• 6430

1. 1

   Test System Voltage: Use a multimeter to check the voltage at the battery terminals with the engine off (should be ~12.6V), and then with the engine running.

2. 2

   Check Alternator Output: Because this is a high-voltage code, the most common underlying cause is a failed voltage regulator inside the alternator, causing it to overcharge the electrical system.

3. 3

   Inspect Wiring and Connections: Check the wiring harness leading to the PTA transmission controller for any shorts to a higher voltage source.

4. 4

   Check Grounds: Ensure all cab, chassis, and engine grounds are clean and tight. A floating ground can sometimes cause erratic voltage readings at the module.

1. 1

   Verify the Overcharge

   Start the tractor and measure the voltage across the battery terminals. If the voltage climbs above 15V–18V, shut off the engine immediately to prevent frying the PTA module or other ECUs.

2. 2

   Address the Charging System

   If an overcharge condition is confirmed, replace the alternator (or its internal voltage regulator, if serviceable).

3. 3

   Clean Connections

   Inspect the main power and ground connections at the battery and the alternator. Clean and tighten as necessary.

4. 4

   Inspect the PTA Module

   Disconnect the harness at the PTA module. Inspect the connector for water intrusion, corrosion, or damaged pins (improper sealing is a known issue that can cause controller malfunctions). Clean with electrical contact cleaner and apply dielectric grease.

5. 5

   Test and Clear Codes

   Reconnect the module, cycle the key switch, and clear the fault codes using a diagnostic tool (such as John Deere Service ADVISOR or Jaltest). Test drive the tractor to ensure the transmission engages and shifts correctly.

6. 6

   Module Replacement (If Necessary)

   If the alternator is outputting normal voltage (approx. 13.5V - 14.4V) but the PTA module still logs 000168.00, the internal power supply monitor of the PTA module has failed. The module itself must be replaced and reprogrammed by a dealer.