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).
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.
THE SOLUTION
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.
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.
LUGGAGE
LAMP
TAILGATE CATCH
MOTOR AND POSITION SWITCH
BODY CONTROL
MODULE (BCM)
Replacement tailgate switch, part number ADN19701, available from FPS
AVAILABLE FROM FPS
TAILGATE SWITCH
Fig 2. The circuit diagram
16 VEHICLE ELECTRONICS
Blue Print supplies the suitable tailgate switch which is identified by
part number, ADN19701. Catalogued on the F:Drive and MAM Autocat,
the switch, alongside other Blue Print parts are available from FPS via
same/next-day delivery. For more information, please speak with your
local FPS representative.
VITAL NEWS ISSUE 51