Thread: Causes and Solutions - Flashing M&S Lights

working on a 2001 Disco 2 .

customer brought it to our Shop in M+S flashing mode ,

as owner says ,he encountered M+S flashing for several times (Limp Home) after 15~20 min of ride (after warm up) .

he did this procedure to solve the problem:turn off the car,wait ,restart...problem solved for hundreds of meters but again repeating!

i took it for a test drive and when M+S appeared ,set it to P,turned off engine, turned on ,put transfer-case to Low ,driven it for 500 Meter ,then shifted back to High,then continued test-drive for 10 Km the problem seemed to be solved ! passed vehicle to owner.

after two weeks Disco came back to our shop with same problem!

i went through almost all suggested tests mentioned in this forum from battery voltage... Wiper on+reverse... fluid level... and XYZ switch (i dismantled and serviced it as done in a post here) but still the problem exist!!!

also the vehicle had 3 amigos on (should it be any related?)

i suspect some issue related with warm-up !? (gets developed by heat)
(also it doesn't go to M+S at cold start)

any idea?

M&S shouldn't be related to 3 amigoes. Whilst M&S can be caused by many things, have you checked the red ecu plug ( if TD5)? If oily, can cause CAN problems as signal wires are where oil goes to/ sits down the bottom. Heat may be causing oil to conduct and short out signal? Car would be running a bit rough as well.
Good oil has lots on 3 amigoes.

thank you bsperka, but it's a V8! tomorrow i'm going to check top solenoid ...as far as i remember at prime test-drive i done ,gear change was sound and perfect . though not convinced if anything's wrong with transmission mechanical-wise!

I had this problem on my td5 I discovered that I was accidentally pressing the buttons on the key while starting.
Turned the ignition off and restarted all was good

The real thing would be a scan with a tester to see the fault codes in engine management, SLABS and EAT(transmission) ECU... even if it's not very common, actually the M+S lights can be triggered by a bad VSS(vehicle speed signal) which is delivered by the SLABS ECU based on ABS sensor signals, not directly but mixing up the engine management it can disturb the engine speed signal or other CAN message to EAT ECU

Originally Posted by "ENGINE MANAGEMENT SYSTEM - V8"

Vehicle Speed Signal (VSS)
The VSS is used, by the ECM, to control idle speed and overrun cut off. The ECM receives the signal through a hard
wired connection direct from the SLABS ECU.
For vehicles fitted with an automatic gearbox, two vehicle speed signals are received by the ECM. The second signal
is derived from the main gearbox output shaft speed, and is sent to the ECM by the Electronic Automatic Transmission
(EAT) ECU though the Controller Area Network (CAN). The ECM compares the vehicle speed signal generated by
the SLABS ECU with that supplied via the CAN.
........
The engaged forward gear is computed from the engine data
input, the engine speed input and vehicle speed.

Anyway there are 19 faults which can trigger the M+S warnings so as long as the XYZ switch was ruled out without a tester IMO it's a guessing game though if you want to go without tester another common cause is chaffed wiring between the EAT ECU and the gearbox, above the gearbox/transfer box area which was covered in post 1

Sort of thought it would be a v8 due to your location. Keep us updated with the fault finding!!

Two other points checked without any positive result:

1-Starter connections were inspected ,all dry and sound.
2-EAT ECU's connector detached and...found some ATF in it (how does it get there! capillary rise? ) ...cleaned and de-greased with contact cleaner spray...mounted in its place dry , and standing with fingers crossed hoping that this may shot-gun it!....but at test drive after 2KM those green devil lights came up flashing again!

i noticed one important thing:

hence driving Disco2, a point just before falling into M+S limp home mode, while accelerator is depressed ,engine makes a tick-over in rev and relatively a clunk heard from transmission ,the M+S comes up flashing meanwhile you can smell un-burnt fuel ,and sometimes as owner remembers there's a black smoke when accelerating (i've not seen it myself).

it sounds to me like a TPS problem or sth related to throttling ,that sends inaccurate signals to ECM , making that tick-over & harsh rich mixture causing desynchronized behavior between Engine and Transmission.

any similar experience?

I say again: plug in a tester and it'll point you to the right direction, your kind if diagnosing things might make you work many hours in vain