Switches & Sensors
Solving the Micra Tailgate Puzzle
BLUE PRINT shares a technical case study on electronic tailgate latches for the popular Nissan Micra.
As automotive technology continues to evolve, purely mechanical systems are transitioning towards being fully electronic or a hybrid of both. The tailgate latch (also known as boot latch) is one of the systems that have evolved for convenience, ease and security. However, the sophistication of this technology can lead to issues.
An example lies in the popular K12 Nissan Micra. The vehicle model has had reports of problematic tailgates where they are unable to open despite the doors locking and unlocking properly. As a result, further investigation was required.
UNDERSTANDING THE MECHANISM
To save valuable time on diagnostic investigations, it is important to understand how the system works.
Normally, the mechanism of the tailgate can only be accessed when the trim from the interior is removed. However, when the tailgate does not open, the technician cannot access the mechanism.
The tailgate release and opening mechanism consists of a micro-switch that is built into the external release switch and a release actuator with a position switch for opening or closing. The position switch is part of the mechanical latch system and all electrical parts are connected to the body control module (BCM).
SO WHY IS IT FAILING?
When the external tailgate release switch is pressed, it completes the circuit to ground. The tailgate release actuator then receives a release signal from the BCM, opening the tailgate. This signal is also incorporated into the vehicle’s alarm system and dashboard symbol illumination to inform the driver when the tailgate is open.
The Micra’s problem was not a simple issue of a mechanical tailgate latch that had seized or broken. Thus, a suitable diagnostic tool had to be used to help find the problem.
Micras are not fitted with an internal release button for the tailgate. However, it appears as a function in the actuator test menu of the diagnostic tool. When this function is used, the latch would open, proving that it was an electrical fault that caused the failure.
In this case study’s scenario, it was suspected that the issue involved the micro-switch. The connector to the switch was found and the latch was closed without shutting the tailgate. With the electrical connector separated, a suitable bridging wire was used to replicate the switch operation. The latch actuator operated and the latch was opened, proving that it was an external switch and not a wiring, or BCM fault.
When faced with this scenario, it is advised that the faulty switch is removed and replaced before refitting it to the tailgate handle. A test of the system should be carried out before closing the tailgate to ensure that the system is in working order. Only then should all the trim parts be refitted.
Blue Print supplies the suitable tailgate switch which is identified by part number, ADN19701.