Case IH t75 – PCU (Pump Control Unit): ADC In PCU, Data Valid But Above Normal Range

The Analogue to Digital Converter (ADC) in the Pump Control Unit (PCU) failed a plausibility check between ground and the remaining ADC channels. When this fault is triggered, the tractor typically enters a 'limp home mode,' which restricts the engine speed to a maximum of 1760 RPM to prevent further damage.

• MXM
• MXM Series
• MXM 120
• MXM 130
• MXM 135
• MXM 140
• MXM 150
• MXM 155
• MXM 165
• MXM 175
• MXM 180
• MXM 190

1. 1

   Access Diagnostic Mode using the diagnostic test switch (Tool No. 380000488) in the tractor's diagnostic connectors (C125) to verify the active 3618 service tool error code

2. 2

   Inspect the PCU and clutch pedal connectors for physical damage, pushed-out pins, or corrosion

3. 3

   Test the clutch pedal potentiometer by disconnecting C077 and measuring resistance between pin 2 and pin 3 (should be 0.90K to 3.7K Ohms)

4. 4

   Check the resistance between C077 pin 2 and C077 pin 1 to ensure the potentiometer sweep is smooth and within range

5. 5

   Check the wiring harness between the clutch pedal potentiometer and the PCU for shorts to a high source or open circuits

1. 1

   Clean and Reseat Connectors

   If the diagnostic checks reveal dirty or loose connectors, clean the pins with electrical contact cleaner, reseat them firmly, and clear the code to see if it returns.

2. 2

   Replace Potentiometer

   If the clutch pedal potentiometer fails the resistance sweep test (reads outside of the 0.90K - 3.7K Ohm range or shows dead spots), remove the faulty potentiometer and install a new one.

3. 3

   Repair Wiring Harness

   If the potentiometer tests good but the fault persists, locate the faulty wire in the harness. Disconnect the affected connectors, carefully remove the harness outer covering, and splice in a repair using an OEM harness repair kit. Ensure correct pin removal and insertion tools are used.

4. 4

   Perform Transmission Calibration

   Whenever a potentiometer is replaced, a mechanical repair is made, or the non-volatile memory is reset, you MUST perform a Transmission/EDC Calibration Set Up Procedure (specifically the H1 Clutch and Synchroniser Calibration). Start the engine, set engine speed to 1200 ERPM, and follow the H-menu prompts until 'END' displays on the gear module.