New Holland TRANS 146 – Transmission Controller (TRANS / TCU): Regulated system pressure low (below 100PSI / 689 KPA)

The transmission controller measures the hydraulic pressure at the regulator valve using a transmission system pressure sensor. When the sensor detects that the regulated pressure has dropped below the minimum operational limit of 100 PSI (689 kPa), the system logs this fault. This can be caused by a failing pressure sensor, damaged wiring, a sticking regulator valve, or an actual loss of hydraulic pressure from the charge pump.

• T6
• T7
• T8
• T9
• T6030
• T7.270
• T8.320
• T9020
• T9050
• TG
• TJ
• TM
• TG215
• TJ480
• TM175
• TM190
• CR
• CX
• CR9090
• CX8080

1. 1

   Verify that the transmission/hydraulic fluid is at the correct level and that hydraulic filters are not clogged.

2. 2

   Inspect the wiring harness leading to the transmission pressure sensor for chafing, corrosion in the connector, or an open/shorted circuit.

3. 3

   Use a multimeter to verify the pressure sensor is receiving its 5V reference supply and outputting a voltage within the 0.5V to 4.5V range.

4. 4

   Connect a manual hydraulic pressure gauge to the diagnostic test port on the transmission regulator valve block to determine if the issue is electrical (gauge reads above 100 PSI) or mechanical (gauge reads below 100 PSI).

1. 1

   Prepare machine for service

   Park the machine on a level surface, lower all implements, relieve hydraulic pressure, and turn off the engine.

2. 2

   Locate pressure sensor

   Locate the transmission pressure sensor on the transmission regulator valve block.

3. 3

   Disconnect sensor harness

   Disconnect the electrical harness connector from the sensor.

4. 4

   Remove faulty sensor

   Unthread the faulty sensor. Have a catch pan ready, as a small amount of hydraulic fluid will escape.

5. 5

   Install new sensor

   Install the new OEM pressure sensor/transducer and tighten to the manufacturer's torque specification.

6. 6

   Test sensor repair

   Reconnect the wiring harness, clear the fault codes via the diagnostic menu, and test drive the tractor to ensure the code does not return.

7. 7

   Remove regulator valve (if mechanical failure)

   If actual pressure is low (confirmed by manual test), remove the transmission pressure regulator valve.

8. 8

   Inspect and clean/replace regulator valve

   Inspect the valve spool and springs for scoring, broken springs, or debris holding the valve open. Clean the valve body or replace the regulator valve assembly if damaged.

9. 9

   Inspect transmission charge pump

   If the regulator valve is functioning correctly, the transmission charge pump (tandem gear pump) must be inspected for internal wear and replaced if it cannot maintain flow.

10. 10

    Replace fluid and filters

    Drain the hydraulic fluid and replace the transmission hydraulic filters to remove any contaminants that may have caused the valve to stick or the pump to wear.

11. 11

    Refill and bleed system

    Refill with approved New Holland transmission/hydraulic fluid, bleed the system, and verify pressure has returned to normal operating ranges.