Case IH P85 – PCU (Power Control Unit): RAM in PCU, data valid but above normal range

This code indicates an internal memory (RAM) fault or corruption within the controller's microprocessor. The controller is receiving or processing data that falls outside of its programmed normal operating parameters, pointing to a failure in the module's internal memory retention or processing capability.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• TM115 through TM165

1. 1

   Check for accompanying transmission calibration codes (such as F24, E24, or 24) which indicate that the non-volatile memory has been reset (H8) or that a calibration is missing

2. 2

   Verify the PCU power supply and ground connections, as voltage spikes or poor grounds can sometimes cause temporary RAM faults

3. 3

   Clear the fault codes and attempt to run the H1 Transmission Calibration procedure to determine if the RAM fault is a hard failure

1. 1

   Replace the PCU

   Disconnect the battery, locate the Transmission Control Module/PCU (usually located in the right-hand console or under the cab floor depending on the exact cab configuration), and replace it with a new or remanufactured unit.

2. 2

   Enter Calibration Mode

   After installing the new PCU, you must perform a full Transmission/EDC Calibration Set Up Procedure. Turn the key switch to ON while accessing the 'H' menu via the diagnostic connector.

3. 3

   Perform H1 Transmission Calibration

   Block the wheels (front and rear) and apply the parking brake. Start the engine and set the engine speed to 1200 ERPM (± 100). Press and hold the High and Low range buttons simultaneously until 'CAL' appears in the transmission display, then release. Follow the on-screen prompts to calibrate the clutch packs and synchronizers. Once calibration is complete, turn the key off to store the new values in the PCU's non-volatile memory.