Case IH P20 – PCU (Powertrain Control Unit) / Engine Control Module: After-Run Not Completed, Data Valid But Below Normal Range

The tractor's electronic control system failed to complete its standard 'after-run' sequence when the machine was shut down. The controller received a valid signal during this phase, but the voltage or time duration fell below the minimum expected threshold to register a successful completion.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190

1. 1

   Check battery voltage and ensure it is not dropping too rapidly when the alternator stops charging.

2. 2

   Verify operator shutdown procedure to ensure the battery disconnect switch is not being used immediately after turning off the key (system requires 60–120 seconds to complete after-run).

3. 3

   Inspect the wiring harness and connectors at the PCU/ECU for corrosion, moisture, or loose pins. Measure circuit resistance with power OFF to ensure continuity.

4. 4

   Test the main power relay and the ECU power relay to ensure they are not sticking or dropping prematurely.

1. 1

   Verify Operator Procedure

   Confirm that the battery isolator/disconnect switch is not being thrown immediately upon engine shutdown. Instruct operators to wait at least 2 minutes after key-off before cutting main battery power.

2. 2

   Clean Connections

   Disconnect the battery. Remove the connectors at the PCU/ECU and the main power relays. Clean them with electrical contact cleaner and apply dielectric grease to prevent voltage drops.

3. 3

   Replace Faulty Relays

   If the ECU power relay fails to hold the circuit open for the required after-run duration, replace the relay.

4. 4

   Clear and Retest

   Reconnect the battery, start the tractor, let it run for a few minutes, and perform a normal key-off shutdown. Wait 2 minutes, turn the key back on, and use the EIC or a diagnostic scanner to verify if the T20 code has cleared or returned.