John Deere 1136.02 – Engine Control Unit (ECU): Engine Control Unit Temperature Sensor Fault / ECU Temperature Signal Invalid

The Engine Control Unit (ECU) has detected that the signal from its internal temperature sensor is invalid, intermittent, or missing. This sensor monitors the physical temperature of the circuit board inside the module to prevent overheating damage. Because the sensor is built directly into the module's circuitry, it cannot be serviced or replaced independently.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5090M
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8R/RW Series (8245R to 8400R)
• 8310RT
• 8335RT
• 8360RT
• 318E
• 319E
• 320E
• 323E
• 30G
• 7180
• 7280
• 7380
• 7480
• 7580
• 7780
• 7980
• 3029 PowerTech engines
• 4045 PowerTech engines
• 6068 PowerTech engines
• 6135 PowerTech engines

1. 1

   Check the physical mounting location of the ECU. Ensure it is not being subjected to extreme external heat (e.g., missing exhaust heat shields, debris packing around the module, or restricted engine bay airflow).

2. 2

   Verify the unswitched power fuses (e.g., F3 10A fuse on E-series loaders) and ground connections to the ECU. Poor voltage or a bad ground can cause the ECU's internal 5V reference to fluctuate, leading to invalid internal sensor readings.

3. 3

   Check with a John Deere dealer to see if there is a software update (reflash) available for your specific machine. Software glitches can sometimes trigger false internal temperature faults.

1. 1

   Disconnect battery

   Disconnect the machine's negative battery cable to prevent electrical spikes.

2. 2

   Disconnect wiring harnesses

   Disconnect the main wiring harness connectors from the Engine Control Unit (ECU).

3. 3

   Unbolt ECU

   Unbolt the ECU from its mounting bracket on the engine block or firewall.

4. 4

   Install replacement ECU

   Install the replacement ECU and torque the mounting bolts to OEM spec.

5. 5

   Reconnect wiring and battery

   Reconnect the wiring harnesses and the battery.

6. 6

   Dealer Programming

   A certified John Deere technician must connect the Service ADVISOR tool to flash the ECU with the correct payload for your specific Engine Serial Number (ESN) and calibrate it to the machine.