Deutz-Fahr 614 – ECU: Ambient Air Temperature Sensor Fault

The Engine Control Unit (ECU) has detected that the voltage from the ambient air temperature sensor is below the normal operating range, indicating a short circuit to ground or a faulty sensor. The ECU uses this sensor data to optimize engine performance, manage fuel injection timing, and control emissions systems such as the DEF heater. When this fault is active, the ECU will typically default to a pre-programmed ambient air temperature value.

• 5120
• Agroclimber V 70
• Agroclimber V 80
• Agroclimber V 90
• Agroclimber V100
• Agroclimber V 105
• Agrofarm 85
• Agrofarm 100
• Agrotron

1. 1

   Visually inspect the ambient air temperature sensor and its connector for physical damage, corrosion, or moisture intrusion.

2. 2

   Inspect the wiring harness for chafing, melting, or cuts, particularly where it might rub against the chassis or engine components.

3. 3

   Use a diagnostic tool to check for other active fault codes (such as SPN 171 FMI 3), which could indicate a broader wiring harness issue or shared ground/power circuit fault.

4. 4

   Disconnect the sensor and inspect the connector pins for damage, corrosion, or being backed out.

5. 5

   Test for a short to ground: With the sensor disconnected and ignition on, use a multimeter to measure voltage between the signal wire at the harness connector and a known good ground. A reading of 0 volts indicates a short to ground.

6. 6

   Test sensor resistance: Disconnect the sensor and measure resistance across its terminals. Compare to manufacturer specifications (e.g., ~37 kOhms at 20°C, ~3.8 kOhms at 80°C). Resistance should decrease as temperature increases.

7. 7

   Verify the Engine Control Module has the correct and latest calibration to rule out software issues.

1. 1

   Repair wiring and connectors

   If any damage, corrosion, or loose connections are found in the wiring harness or connector during diagnostics, repair or replace the affected parts. Ensure all connections are clean and secure.

2. 2

   Replace the ambient air temperature sensor

   If diagnostic checks confirm the sensor is faulty or shorted, locate the sensor (often near the front grille or bumper), disconnect the electrical connector, remove the retaining clip or bolt, and install a new sensor securely.

3. 3

   Clear fault codes

   After completing the repair, use a diagnostic tool to clear all active and inactive fault codes from the ECU.

4. 4

   Verify the repair

   Start the engine and let it idle for at least one minute to allow the ECU to run its diagnostics. Check the live data on a diagnostic tool to ensure the ambient air temperature reading is plausible and the fault does not return.