Case IH 3588 – Engine Control Unit (ECU) / EDC: Plausibility check of catalyst system - Ambient Temperature of Humidity Sensor or both Catalyst Temperatures not plausible.

This code indicates that the readings from the ambient temperature/humidity sensor and the Selective Catalytic Reduction (SCR) exhaust gas temperature (EGT) sensors (upstream and downstream of the catalyst) do not logically correlate with one another.

• Magnum
• Steiger
• Puma
• Maxxum
• Optum
• Farmall
• Patriot
• Axial-Flow

1. 1

   Inspect the wiring harness leading to the ambient temperature/humidity sensor and both SCR catalyst temperature sensors for cracked insulation, chafing, or melted wires.

2. 2

   Disconnect the sensors and inspect the connector pins for corrosion, moisture, or loose terminals.

3. 3

   Use the CNH Electronic Service Tool (EST) to monitor live data from the ambient humidity sensor and both EGT sensors for signal dropouts, erratic jumps, or stuck default values.

4. 4

   Check for accompanying fault codes (such as 3589 or 3591) to help isolate whether the issue is the upstream, downstream, or ambient sensor.

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent electrical spikes.

2. 2

   Clean and Repair Connections

   If the diagnostic check revealed dirty or corroded connectors, clean them thoroughly with electrical contact cleaner. Apply dielectric grease to the seals to prevent future moisture intrusion. Reconnect and test.

3. 3

   Replace Faulty Sensor

   If a specific sensor was identified as dead or out-of-range via the EST live data, locate the faulty sensor, carefully unscrew it (penetrating oil may be required), install the new replacement sensor, and tighten to OEM torque specifications. Route the wiring harness away from direct heat sources and secure it with zip ties.

4. 4

   Clear Codes

   Reconnect the battery and use the CNH EST diagnostic software to clear the inactive fault codes from the ECU.

5. 5

   Perform a Healing Procedure

   Run the tractor under a heavy load to generate high exhaust heat (often over 425°F for at least 30 minutes) so the ECU can run a new plausibility check and verify the sensors are now reading correctly to clear the power derate.