CLAAS Id7770h / 7770h (1172 03) – ENG (A15): Input voltage of the turbocharger intake air temperature high

The engine control unit is receiving a voltage signal from the intake air temperature sensor that exceeds the normal operating range, typically pointing to an open circuit or a short-circuit to the battery positive (+). When this fault is active, the engine calculator defaults to a substitute intake air temperature value of 30°C to keep the machine operational, which may result in reduced engine performance.

• CLAAS Axion 850
• CLAAS Arion 640
• CLAAS Arion 650
• CLAAS Arion 620
• CLAAS Arion 550
• CLAAS Arion 530
• CLAAS Arion 510
• CLAAS Celtis

1. 1

   Check the Intake Air Temperature Sensor (Component B1) for physical damage and internal resistance to ensure it is not internally open.

2. 2

   Verify the connections at the engine ECU (ENG A15).

3. 3

   Check the wiring harness between the B1 sensor and the A15 module for any open circuits or short-circuits to a 12V power source.

4. 4

   Check the sources of energy (fuses, supply voltage, and ground connections).

5. 5

   Verify the component's operating conditions (e.g., check for mechanical seizing, extreme temperatures, or pressure issues in the intake).

1. 1

   Verify the Code

   Connect a diagnostic tool to the diagnostic plug (e.g., PRO-LINK) to confirm that code 1172 03 / Id7770h is currently active.

2. 2

   Locate the Sensor

   Locate the intake air temperature sensor (Component B1) on the turbocharger compressor inlet / intake manifold.

3. 3

   Inspect the Harness

   Disconnect the sensor and inspect the connector pins for corrosion, moisture, or pushed-out pins.

4. 4

   Test the Circuit

   Using a multimeter, test the signal wire going back to the ENG (A15) module for continuity and ensure it is not shorted to voltage.

5. 5

   Test the Sensor

   Measure the resistance across the sensor's terminals. If the resistance is out of specification (indicating an open internal circuit), the sensor is defective.

6. 6

   Replace if Necessary

   If the wiring is intact but the sensor fails testing, replace the B1 Intake Air Temperature Sensor.

7. 7

   Clear and Verify

   Reconnect the sensor, clear the fault codes from the ENG (A15) module, and run the engine to verify that the ECU is reading live temperature data rather than the 30°C default.