DTC Fiat U1705-87 Short Explanation
Channel: Maxidot
Date: 2020-12-19

The video focuses on the basic Fiat specific diagnostic error code.
Contents:
0:21 Basic DTC analysis according to OBD2 protocol standard.
1:48 Insight into programming
- an explanation of what a bit is and how a byte is formed
- decoding the Error Code to the base programming
2:58 A diagnostically understandable description of the Diagnostic Trouble Code
3:05 Basic error definition
- Possible causes or errors of the car and its parts describing the mentioned error

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Make:
FIAT
Code:
U1705 87
Definition:
HECU Fault
Description:
Enable Conditions: Case 1: The electrical feedback signal does not match the actuation signal for the corresponding valve for more than 30 ms.- Current controlled valves and under voltage conditions :detection time is 80 ms Case 2: A Fault is found if UVR is not within 0.1battery voltage valve relay voltage 0.8battery voltage. A Fault is found if valve relay voltage ≥ 0.2battery voltage. After that all valves are switched on sequential,valve relay voltage and valve feedback is measured.Case 3: The valve and pump motor test detects electrical actuation malfunction of ABS valves.The test actuates all valves in series (to detect short cuts or shunts between the valve lines).Faults are detected if there is an error during the test.Case 4: The drift test is executed only once during an ignition Cycle. If it detects partly shorted valve coils, almost inoperative coils or malfunction of the valve driver,a failure is recognized.
Cause:
 Faulty HECU
Failure Type:
Missing Message
This sub type is used for failures where one (or more) expected message(s) is not received, e.g., periodic transmission where the repetition time is too high, or message not received as a result of unforeseen reset events of the concerning component (e.g. engine control unit communicating with ABS).