Case IH 73 – Transmission ECM: ECM (2) SUPPLY VOLTAGE (12VF) IS TOO HIGH

When the tractor is turned on, the ECM detects that the voltage at ECM connector 2, pin 34 or ECM connector 2, pin 10 has spiked above 18 volts for longer than 0.3 seconds. The transmission is critically disabled to protect the electronic components from overvoltage damage.

• JXC
• JX55
• JX60
• JX65
• JX70
• JX75
• JX80
• JX85
• JX90
• JX95
• JX1060C
• JX1070C
• Farmall 65C
• Farmall 75C
• Farmall 85C
• Farmall 95C
• 105U
• 115U
• TN55
• TN60A
• TN70A
• TN75A
• TN85A
• TN95A
• TNDA
• TNSA
• TD
• TL
• T4

1. 1

   Verify if H9, channel 3, is above 762 using the dealer diagnostic tool.

2. 2

   Using a multimeter, check the battery voltage with the tractor off.

3. 3

   Start the tractor (if possible) and measure the voltage at the battery terminals. If the reading exceeds 18 volts, the alternator's internal voltage regulator has failed and is overcharging the system.

1. 1

   Disconnect Power

   Disconnect the negative battery cable to prevent any further electrical damage to the Transmission ECM.

2. 2

   Inspect the Battery

   If the battery is damaged from being overcharged (e.g., boiling, swollen, or failing a load test), replace the battery.

3. 3

   Replace the Alternator

   If the alternator is outputting >18V, the internal regulator is blown. Remove the serpentine/drive belt, disconnect the electrical connections (B+, D+, W terminals), and unbolt the faulty alternator. Install the new alternator and tension the belt to spec.

4. 4

   Clear the Code

   Because this is a "Fixed" code, you must use a diagnostic tool or the tractor's onboard diagnostic reset procedure to clear the code from the Transmission ECM memory. The transmission will remain critically disabled until the code is cleared.