Case IH 2662 – ZTC: Hydrostatic unit positive solenoid is shorted to power

The control module has detected that the electrical circuit supplying the positive proportional solenoid on the hydrostatic drive unit has a short circuit directly to a power source (B+). This prevents the controller from properly modulating the solenoid, which can lead to erratic transmission behavior, failure to shift, or a complete loss of hydrostatic drive.

• Steiger T4B
• Puma CVX Series (165, 180, 195, 210, 225)
• Maxxum Series
• Steiger Series
• Magnum Series

1. 1

   Check for improperly connected external power supplies or jump-starters, which can cause system-wide overvoltage or short-to-power codes.

2. 2

   Identify Circuit 7847 (typically a Light Blue / 'TQ' or 'LB' wire) for the transmission hydrostatic positive solenoid.

3. 3

   Disconnect the electrical connector at the hydrostatic positive solenoid (located on the transmission valve manifold) to isolate the component.

4. 4

   Test the harness for a short to power: Turn the key ON (engine OFF) and use a multimeter to measure voltage at the harness connector. If 12V (B+) is present on the signal wire when not commanded, the wiring harness is shorted to power between the ZTC/TCM and the solenoid.

5. 5

   Test the solenoid for an internal short: Measure the resistance across the solenoid pins and from the pins to the solenoid housing (ground). If there is continuity to the housing, the solenoid is internally shorted.

1. 1

   Depressurize the System

   Turn off the tractor, lower all implements, and relieve all hydraulic pressure before working near the transmission valve manifold.

2. 2

   Disconnect the Battery

   Disconnect the negative battery cable to protect the ZTC controller from static spikes during repair.

3. 3

   Access the Valve Manifold

   Locate the hydrostatic unit on the side of the CVT transmission. Identify the positive solenoid (usually paired next to the negative solenoid, circuit 7848).

4. 4

   Repair the Short

   If the harness failed the diagnostic test: Trace Circuit 7847 back to the ZTC controller. Look for pinch points, melted insulation, or areas where the wire is rubbing against a live 12V wire. Repair the damaged wire and apply heat-shrink tubing. If the solenoid failed the diagnostic test: Unbolt the retaining bracket for the positive solenoid. Remove the faulty solenoid cartridge from the manifold. Lubricate the O-rings on the new solenoid with clean hydraulic oil and install it into the manifold.

5. 5

   Reassemble and Clear Codes

   Reconnect the battery, turn the key ON, and use the AFS Pro display or an EST (Electronic Service Tool) to clear the inactive 2662 fault code.

6. 6

   Test Operation

   Start the tractor and test the forward/reverse shuttle and CVT speed modulation to ensure the hydrostatic unit responds correctly.