W163 ML270 2002 722.6 won't engage any gears!

Blueyes1971

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hi again all..

So I was in cruise control doing 50mph when the revs surged and dropped to tickover.
Lucky I managed to coast safely to a stop and discovered engine running fine but although I can change gears with the selector, neither reverse or drive will actually engage.
Also, in park or neutral , I can Rev engine as normal to any degree but in reverse or drive the revs are restricted to 1000rpm.
I have over the past few months experienced a little slipping into the higher gears if I put my foot down a little but this final event happened with no warning , no noise etc ...simply disengaged.
Also there is no noise to speak of when I try selecting gears now either.
For a long time prior to this last event when selecting reverse, there was a pause and sometimes a small clunk as it engaged.
The selector rod from the gearstick if you will to the transmission is properly connected at least on the exterior of the transmission and the rod bush is present and intact with little or no play/slop
I have had the car diagnosed and the codes discovered are:
P2600 LOW VOLTAGE TO CURCUIT 87 TOO LOW
P4404 THE CAN SIGNAL FROM COMPONENT S9/1(BRAKE LAMP SWITCH) OF THE TRACTION SYSTEM IS IMPLAUSIBLE.
P2502 GEAR IMPLAUSIBLE OR TRANSMISSION SLIPPING
P2500 TRANSMISSION HAS IMPERMISSIBLE TRANSMISSION RATIO.

Hopefully this is not fatal and if so I will buy a used trans and rebuild this one in my own time, but would like any advice or experience from you guys as to what is or may be going on here.
I will be fitting a new brake switch in the coming days as I have one on order.
Another thing to bear in mind is I had conductor plate and socket replaced due to limp in 2nd gear done less than 20,000 miles ago...at a cost of £960. They did other trans related stiff also of course.
I've not investigated further due to the weather here in Leicestershire at the moment..kinda working between the rain and work so positive and productive help would be grately received.

Thanks...Kevin
 

Arudge

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CLK200 2000 Kompressor
hi again all..

So I was in cruise control doing 50mph when the revs surged and dropped to tickover.
Lucky I managed to coast safely to a stop and discovered engine running fine but although I can change gears with the selector, neither reverse or drive will actually engage.
Also, in park or neutral , I can Rev engine as normal to any degree but in reverse or drive the revs are restricted to 1000rpm.
I have over the past few months experienced a little slipping into the higher gears if I put my foot down a little but this final event happened with no warning , no noise etc ...simply disengaged.
Also there is no noise to speak of when I try selecting gears now either.
For a long time prior to this last event when selecting reverse, there was a pause and sometimes a small clunk as it engaged.
The selector rod from the gearstick if you will to the transmission is properly connected at least on the exterior of the transmission and the rod bush is present and intact with little or no play/slop
I have had the car diagnosed and the codes discovered are:
P2600 LOW VOLTAGE TO CURCUIT 87 TOO LOW
P4404 THE CAN SIGNAL FROM COMPONENT S9/1(BRAKE LAMP SWITCH) OF THE TRACTION SYSTEM IS IMPLAUSIBLE.
P2502 GEAR IMPLAUSIBLE OR TRANSMISSION SLIPPING
P2500 TRANSMISSION HAS IMPERMISSIBLE TRANSMISSION RATIO.

Hopefully this is not fatal and if so I will buy a used trans and rebuild this one in my own time, but would like any advice or experience from you guys as to what is or may be going on here.
I will be fitting a new brake switch in the coming days as I have one on order.
Another thing to bear in mind is I had conductor plate and socket replaced due to limp in 2nd gear done less than 20,000 miles ago...at a cost of £960. They did other trans related stiff also of course.
I've not investigated further due to the weather here in Leicestershire at the moment..kinda working between the rain and work so positive and productive help would be grately received.

Thanks...Kevin
I've had a similar experience albeit on petrol not diesel. We can break your error codes into two groups, the first two the cause, the second two the effect. The engine dropping to tickover is the ECU protecting the engine because something has occurred that the ECU doesn't like. On mine there was light corrosion on the engine ECU plugs. Two plugs were corroded and one saturated with oil that had wicked it's way up from the camshaft sensor. On yours the brake light switch is a known issue, i'm told its £8 and fitted in seconds, the low voltage will be a poor connection, albeit corrosion or poor earths, check your engine ECU multipin plugs for corrosion, even slight white corrosion or the dreaded verdigris will cause problems.

Good luck.
 
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Blueyes1971

Blueyes1971

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Oil level checked hot and cold both ok
Engine ecu all plugs / connectors checked for any signs of ingress or corrosion all ok
Now onto transmission ecu for inspection when I find it...believe it's under dash in a footwell so will report back once I've found and checked....I'm on this all day any updating in realtime if anyone what's to suggest and get real time replies and results.

Thanks
 
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Blueyes1971

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Ok...so searching in the driver footwell for the transmission ecu...I can see what appears to be a module to the left right beside / behind the e brake pedal....touching the loom for oil ingress I find its evident its saturated in oil...so I'm guessing I've found the trans ecu...can anyone please confirm this and if so, any ideas how to remove this module and any tips or experience with this issue will be much appreciated.
I'm guessing brake cleaner and contact servisol type electrical cleaner or just the latter.
Most importantly the best way to get this module out from its location.
One last thing....would this oil saturated module throw up the codes mentioned in first post and if so, would this oil saturated module completely shut down the transmission as I'm experiencing?
I hope I've finally found the issue and fingers crossed its not trans terminal.
Cheers guys in advance.
 

Arudge

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Ok...so searching in the driver footwell for the transmission ecu...I can see what appears to be a module to the left right beside / behind the e brake pedal....touching the loom for oil ingress I find its evident its saturated in oil...so I'm guessing I've found the trans ecu...can anyone please confirm this and if so, any ideas how to remove this module and any tips or experience with this issue will be much appreciated.
I'm guessing brake cleaner and contact servisol type electrical cleaner or just the latter.
Most importantly the best way to get this module out from its location.
One last thing....would this oil saturated module throw up the codes mentioned in first post and if so, would this oil saturated module completely shut down the transmission as I'm experiencing?
I hope I've finally found the issue and fingers crossed its not trans terminal.
Cheers guys in advance.
I've used brake cleaner myself in the past but it's not clever, its aggressive stuff and attacks some plastics. Stick to contact cleaner.

Mine is in the passenger footwell so I can't help you there.

In theory the oil shouldn't make any difference. It's a dielectric and the electrics in the transmission are submerged in it. But in practice the oil in the cabling can create capacitance and upset digital signals. Clean it out and get the transmission plug upgrade.
 
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Blueyes1971

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Well I'm still dubious as to this being the issue...less than 20,000 miles ago I had £1000 worth of work done on the trans...conductor plate etc..and I'm sure they said they replaced the loom with an upgraded one...but the cables I'm touching around by the connector are soaking...so if it has an upgraded plus to ecu then I'm guessing that was to stop ingress...but I won't know for sure until I remove the unit from the footwell...but with almost 60 views and you are the only input besides myself, ..looks like advice on this matter is thin on the ground ...thanks for your thoughts and time to be involved.
Truly do appreciate it.
I'll post back with my findings shortly when I've go it out
 
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Blueyes1971

Blueyes1971

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Ok this connector is first out and have no idea what it is.. it's also oil soaked
Anyone know what it is in relation to??
 

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Blueyes1971

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Still awaiting confirmation as to what that connector is from / goes to etc .
Finally got the trans module out and looks brand new and was obviously replaced during the trans work previously... the unit itself is resting on paper as we speak in a way that if there is any oil inside it should come out ... there's not a cup full inside like some I've heard of but there is some... here is what has come out in the last 5 mins
 

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Blueyes1971

Blueyes1971

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One of the plugs and it's relative wiring is saturated... could do with any advice as to how to open this module to clean thoroughly... I'm guessing this also suggests that the plug seal to connector plate at the trans has also failed .. although when I was under there I did not see evidence of that so will have to re check
 
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Blueyes1971

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So got TCM open and no sign of oil ingress inside at least...so just the loom plug to clean out.
And the first connector that I still haven't identified
 

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LostKiwi

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Don't use contact cleaner unless you can be absolutely certain its dry before you reconnect it as some contact cleaners are conductive when wet. Its better to use a switch cleaner as thats non-conductive and can be reassembled wet with no problems.
 
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Blueyes1971

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Thanks...yeah I'm using switch cleaner ....is there anyway to get the connectors open?
 
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Blueyes1971

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Or walking on her carpet ffs
Anymore ideas guys....?
 
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Blueyes1971

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Ok so all cleaned dried and back together.... No change.
Is there any way I can see inside the bell housing while gear lever selecting drive and see if it's at least spinning?.
 
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Blueyes1971

Blueyes1971

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Just found a slightly wet (water) oil cooler at the front....I'm I correct in understanding this is what cools the trans?....I thought it only had oil in this though?
This could account for perhaps overheating trans and therefore shutting down or is there anyway water could have got into trans if the oil cooler shares water and oil?
 

LostKiwi

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Follow the pipework from the transmission to the oil cooler to see if it goes into the radiator. If it does then there was a known problem with Valeo radiators where they would develop a crack that allowed coolant and transmission fluid to mix. This destroys the clutch packs in the gearbox if allowed to go on too long and at the very least caused rough gear changes.

Not all vehicles have a combined radiator/transmission oil cooler so following the pipework is the only way to be sure.
 
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Blueyes1971

Blueyes1971

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Thanks....yeh it appears to just be oil on mine....I guess they changed it for the facelift models
Back to square one
 
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Blueyes1971

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I guess I've not checked the selector rod link at the lever module deep in the centre console.
Anyone heard of those disengaging...I'd imagine it's the same deal as the trans end with a bush and clip.
I better check anyway just in case
 


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