Causes and Solutions - Flashing M&S Lights
Whilst there is a good recent thread on this problem, I thought it was worthwhile pulling together all of the causes and solutions to flashing M&S lights.
The following have been discussed on the AULRO website from time to time as causes of the M&S lights illuminating. Typically associated with this are the gear selector LEDs and display flashing; as well as the automatic transmission being put into ‘limp home’ mode, with only 3rd and 4th gears being selected by the ECU, to protect the transmission.
A low battery may cause the M&S lights to illuminate. From reading AULRO and tests others have done, this appears to occur around 11.6 volts or lower. If the battery is on the way out, then the voltage drop when starting the vehicle will be sufficient to get the M&S lights going.
Charge the battery, check its condition and age, check the charging circuit as to why the battery is low, see if there is a high residual battery drain when the ignition is off, change the battery to an equivalent of at least OEM specification.
Gear Position Switch / XYZ Switch
BTW: This is the typically the first solution everyone suggests.
The gear position switch (inhibitor switch, xyz switch) is a leading cause, but not the only one and without diagnosis or inspection, prior to replacement, may or may not fix the fault. This is a $300 (replacement cost) choice or a couple of hours taking it off, pulling apart etc on a maybe??
A quick test, suggested by Disco Muppet, may help you to determine if you should look at the switch
"Apparently a quick and simple test for the xyz switch is to put the windscreen wipers on
If you put your wipers on, then select reverse then the rear wiper should come on, of the xyz switch is working properly.
Not sure how valid a test it is, but something to consider”
See http://www.aulro.com/afvb/discovery-...le-causes.html for more details.
Common causes switch issues – Air conditioning water leaking onto it. See the link below on the repair routine.
XYZ Inhibitor Switch Repair
Redirect or lengthen the air conditioning tubes
Moving the gear selector too quickly (for example the car was in D whilst trying to start it and the driver moved it into P to get it to start) will provide signals that the transmission ECU will not understand, causing it to go into ‘limp home’ mode.
Either a stop and restart of operations via the ignition switch or a reset of the fault code via the OBD will rectify this cause.
Slow down your behaviour with regards to gear selection.
Several reports about wiring connectors or damage to the wiring harness.
The energiser wire to the Starter solenoid (the thin green wire) has been reported as a problem. Loose oily connection.
Some have reported wires rubbing on the top off the gearbox and shorting together.
See http://www.aulro.com/afvb/discovery-...le-causes.html for more details.
Pretty obvious, but fix the faulty wiring....
Low Fluid Level
Low fluid level in the auto has been reported to cause the M&S lights to illuminate. See http://www.aulro.com/afvb/discovery-...le-causes.html for more details.
Check the fluid level and top up, if required.
Follow the workshop manual on procedures to follow.
http://www.aulro.com/afvb/discovery-...oil-level.html may assist.
From the Workshop Manual
There are 18 listed reasons in the workshop manual why the M&S lights come. Sure, the gear position switch (also called the w,x,y,z switch in RAVE) is first on the list, but there are other reasons. Just because the symptoms seem to be the same as others have listed on AULRO, doesn’t mean that the fault is the same, unless ALL of them match.
See RAVE for more details. Available from the AULRO shop, if you don’t have one.
The existence of an intermediate state (on the W,X,Y,Z switch)causes a fault code to be detected by the BCU. To reduce the chances of the fault condition occurring while changing selector lever position, the inputs are debounced and only considered valid when they have existed for at least 33 ms.
When a Fault is Detected
While the ignition is on, the electronic automatic transmission (EAT) ECU diagnoses the system for faults. The extent of the diagnostic capability at any particular time depends on the prevailing operating conditions, e.g. it is not possible to check torque converter lock-up while the vehicle is stationary, or to check for a short circuit to earth if the circuit concerned is already at a low potential. If a fault is detected, the EAT ECU immediately stores a fault code and the values of three operating parameters associated with the fault. Depending on the fault, there are four possible effects:
After the detection of a fault, the effects remain active for the remainder of the drive cycle. In subsequent drive cycles, as soon as the EAT ECU diagnoses the fault is no longer present, it resumes normal control of the gearbox. The conditions required to diagnose that the fault is no longer present depend on the fault. Some faults require the engine to be started, others require only that the ignition is switched on. After a fault has not recurred for forty warm-up cycles, the fault is deleted from the EAT ECU memory. Only five different faults can be stored in the memory at any one time. If a further fault occurs, the fault with the lowest priority will be replaced by the new fault.
Mechanical limp home
In the mechanical limp home mode, gear engagement is controlled by the manual valve. The gearbox is fixed in 4th gear if the fault occurs while the vehicle is moving, or 3rd gear if the fault occurs while the vehicle is stationary. 3rd gear is also engaged if a vehicle is brought to a stop and the selector lever is moved out of, and back into, D. Neutral and reverse gear are also available.
CAN data bus failure
In the event of a CAN data bus failure any of the following symptoms may be observed:
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Oil in Injector harness can also cause M&S
In the All Four X 4 Service Centre November Newsletter, they report that
"Land Rover TD5 ECU Oil Ingression
If you own a Land Rover fitted with a 5 Cylinder Diesel TD5 Engine you may have already had an experience with this issue. The TD5 Engine fitted to Discovery & Defender between 1999 and 2006 has a history of Oil travelling down the Engine Loom into the ECU.
The symptoms of this is M & S warning Lamp flashing, hard starting, poor performance and running rough. Generally this can be quickly checked by removing the ECU Plug and looking for Oil contamination."
Allan Davidson from Allfourx4 indicates that the reason is that the yellow and white CAN twisted wires on the engine ECU aren't providing the correct (or any) signal to the electronic Automatic Transmission (EAT) ECU, due to the oil corrupting the signal.
If the engine is running rough and the M&S lights are on, check the red ECU harness connector for oil. If present, then this is a likely cause of the M&S lights. The nannocom may show injector faults,. due to the oil ingress.
Short term - Deoil the ECU end of the wiring harness (use degreaser, contact cleaner, brake cleaner etc.)
Replace the injector harness (some on AULRO indicate that it should be considered a service item).
Consider replacing the engine harness every 10 years or so, as well as the injector harness.(another service item!)
Use dielectric grease on connectors.
Thanks to All Four x 4 for their quick response to my queries on this cause.
Here is yet another cause and solution possibility for m&s lights - solenoid plug on top of automatic http://www.aulro.com/afvb/discovery-...hts-fixed.html
Question regarding the M & S lights and loss of gears.
This afternoon my auto went clunk, M & S lights started flashing and felt like it was stuck in 3rd as I was parking it.
Turned off for 15min and restarted, no flashing lights but, I no longer have a fourth gear and the red light on the gear selector will not illuminate in drive, only 1st - 3rd.
1st - 3rd work fine, but no 4th, so sat at 3000rpm at 100km/hr for the last short trip home.
Batteries are fine as I have 2 x 55ah Optimas wired in parallel as a single cranking battery, have not been through significant water etc recently and this was at the very end of a 2,000km trip.
The way I read the above post was "limp mode" will lock the transmission in 3rd gear and not provide normal use of 1st, 2nd & 3rd with only 4th and 4th lockup not available.
Or is it meant to be "limp mode" gives 1st - 3rd gear use???
I have checked the batteries, they are fine, XYZ switch appears to functioning as normal using the test provided in the first post.
The box is getting serviced in a couple of weeks so we shall see if that helps it at all.
Chris ,,Possibly the 3rd entry on this post related to solenoid plugs. Internally they are supposed to be pretty good autoboxes with issues mainly being external things. Check the plug and wiring harness . Im no expert as I have had an intermitant flutter from 2nd to 3rd for over a year now on one of our D2's. Everything had been checked apart from wiring and plugs last week ..and fingers crossed shifts have all been smooth again so far.
Currently disco will not start and these lights are flashing. Normally it is the little c clip thing that is loose/out of place and normally just removing and putting it back fixes my issue. This time however it has done it twice. Stranded in mt barker then removed and replaced c clip on xyz switch twice. Then started and all fine. Fine the next couple stops. Then get home park to unload hay and will not start. Have tried disconnecting battery fir 15 minutes, fiddling with c clip several times. Did the quick check with reverse/rear window wiper and that is fine. About to check fluids. Car has also been making a weird whine today that i put down to transfer box possibly being low as due to do my regular fluid checks. I do know my batteru has been recording low voltage. So is on way out i think. Wish i had nanocom lol
I have had flashing M&S lights on two occasions since owning the D2. On the first it was on start up. The vehicle was in limp home and I am sure it was third gear.
Plugged in nanocom and it came up with fault "can bus timed out." Cleared fault and all was good.
On the second occasion I did not drive it. I just used nanocom, cleared the fault(which I think was the same) and all good. Last one was about four months ago and there was about twelve months between them.
I just put it down to computer gliches.
I was asked " Is it ignorance or apathy?" I replied "I don't know and I don't care."
1996 TDI ES. 2003 TD5 HSE
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