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Stalling TJ Magna
author: Martin "mpot" Pot
first published 6 March 2006
This page describes the long-running issues with my Mitsubishi TJ Magna stalling immediately
after starting, and the the trivial fix for the problem.
Feedback from readers of this page indicates the same issue can occur with the TH Magna too.
Background Info
In early 2002, we bought a 2000 Mitsubishi Magna TJ Advance wagon, with a 3.5L V6 engine.
The car was purchased as a family car, and is driven mostly by my wife.
Several months after it was purchased, the engine would occasionally stall
immediately after being started.
TJ Magna wagon
After several frustrating years of trying to resolve this issue,
including an ECU replacement, the cause was eventually identified,
and a very simple fix rectified the problem.
Symptoms
The engine intermittently stalls several seconds after starting.
Typically, the engine will remain running after 3-5 attempts to start,
but sometimes will take more attempts.
Sometimes the engine will start at the first attempt for several weeks,
before it begins stalling immediately after it starts.
Note that after the engine has stalled, attempting to immediately restart will just
cause the engine to crank, but not fire.
The ignition needs to be turned fully off before attempting to restart it.
On several occasions, after several instances of the car stalling soon after
being started, the engine would fail to fire, but would just continue cranking.
The ECU does not report any error codes, and we were not able to identify any factors
which may be affecting the car (ie, weather, hot vs cold engine, etc).
History
Symptoms first started appearing several months after purchase, but gradually got worse,
until in February 2003, the engine would not start at all.
The car was towed to the nearest Mitsubishi service center, and the ECU was replaced under warrenty.
Approximately 6 months later, the issues re-surfaced, and have intermittently occurred since then.
In the last few weeks, these issues have been occurring more frequently,
with the engine failing to fire at all after several stalled starts.
Some testing with a multimeter indicated that the fuel pump relay de-energises as soon
as the engine stalls, but the engine control relay remains energised.
This seems to indicate the ECU is shutting down the engine for some reason.
I've heard from a number of sources that there is a known issue with the immobiliser in the TJ,
but no-one has been able to provide any specific details.
The car has spent significant amounts of time at various mechanics,
but either the car starts each time for the mechanic, or they cannot determine the cause.
Progress at Last
An appointment was made with a senior technicians at one the local
Mitsubishi service centers, to discuss the ongoing issues with the car
(the 3-year new car warrenty had expired 2.5 years ago).
He confirmed that there are known issues with low battery voltage causing similar symptoms
(where the ECU shuts down the engine if the voltage is too low),
but based on the specific symptoms, these particular issues are unlikely to
be caused by the battery.
He said that some Magna models (including the TJ) have experienced similar issues to the ones
described, which have been traced to
connectivity issues between the immobiliser control module and the engine ECU,
and in some cases, have been resolved by directly soldering the connections to each module.
The technician confirmed the best approach forward is to connect a diagnostic unit to the
immobiliser to check for error codes. The connectivity between the immobiliser control
module and the ECU should also be investigated, to determine if a bad termination is
causing the issues.
The Fix
The Haynes Repair Manual includes detailed wiring diagrams, and the
connection between the immobiliser control unit and the ECU was quickly located.
Note that the immobiliser control unit is one of the components in the Body Electronics
Module (BEM).
extract of wiring diagram with link highlighted in red
The Engine Electronic Control Unit (ECU) is mounted in the centre console,
underneath the stereo, and is somewhat difficult to
access, requiring the removal of parts the dash.
The Body Electronics Module (BEM) is located
underneath the dash, near the steering column, and is relatively easy to access,
without requiring any tools.
A closer look at the BEM revealed it has three large connectors linking it to the
wiring loom.
location of Body Electronics Module under the dash
The wiring diagram shows the link between the BEM and the ECU as
being a solid brown wire, and this was quickly traced to the third connector, located on the
driver's side of the BEM.
the BEM connector linking to the immobiliser control unit
Several attempts to start the engine confirmed it would stall each time it was started.
This BEM connector was then unplugged and re-inserted, with the connector being firmly
pushed in, to ensure it was properly seated in the socket.
The engine has since started and run normally every time.
Conclusion
The issues were caused by a bad contact in one of the connectors linking the
immobiliser control unit (in the BEM) to the ECU, causing the ECU to shutdown the engine within
seconds of it starting, due to an incorrect signal from the immobiliser control unit.
The ECU replacement several years ago did not address the real issue, but
caused the symptoms to go away temporarily, as the act of re-connecting
the connectors to the BEM provided a better connection between the immobiliser control unit
and the ECU.
However, after approximately 6 months, the same connection must have once again
suffered from the same issues, possibly caused by oxidisation between the
connector terminals.
The intermittent nature of the issue caused a lot of frustration over a period of
several years, with my wife being stranded several times when the car would refuse
to start at all.
Various mechanics and technicians failed to find the cause, and in most cases, could not
even reproduce the problem.
In the end, it was a very simple and cheap fix for this problem,
and I'm publishing this information on the web, in the hope that it will assist
anyone else with similar issues with their Magna.
Addendum: More Issues
(added February 2012)
After a number of years of trouble-free motoring, the annoying stalling issue reared its head again!
This time, I traced it down to a bad connection in the wiring to the antenna around the keyhole.
ignition barrel under the dash
1: antenna and keyhole lighting ring
2: antenna connector
The white ring around the keyhole is both a lighting ring (to make it easier to find the keyhole in the dark),
and an ignition key antenna. The antenna is used by the Body Electronics Module (BEM) to communicate with the electronics inside
the key, and if an appropriate signal isn't received, the BEM shuts down the ECU within seconds of the engine starting.
The wiring from the antenna goes through a connector mounted immediately below the steering column
(identified as "2" in the photo above), and it was this connector that was causing the issues.
Simply pulling this connector apart, then plugging it back together resolved the issue for me.
Testimonials
I have received emails from several people who found this page on the web
after experiencing similar issues with their Magna.
Once the cause of the issue was identified (based on the info on this page), these
people were able to resolve their issues too.
This confirms that this is not an isolated incident, but appears to occur on various
Magna models. The intermittent nature of the fault can make it very difficult to
identify the cause, and that's one of the main reasons why I have published
this information on the web.
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