sukyb

Have a C220 Coupe Semi auto (2002), having serious issue with transmission. Have had relay, pump and now the control module replaced but still get the car Failing and going into limp mode. Switching off and on works until the next time it happens totally random. Error codes found via STAR machine are P2080 Pressure too low and P2081 Hydraulics something...A friend is doing the diagnostics..any guidance greatly appreciated.

Thanks
Suky

Xhale707

P2080 Exhaust Gas Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 1)
P2081 Exhaust Gas Temperature Sensor Circuit intermittant (Bank 1 Sensor 1)

Those two codes this is what i got from a mercedes website.

Code P2081 relates to the Left side downstream O2 sensor.
Code P2082 relates to the Left side upstream O2 sensor.

sukyb

Hi,
Sorry it's not those as described by the previous post, the codes are correct as P2080 but description in star software says Pressure too low or hydraulic pressure too low, 2 codes are stored under transmission, P2080 and P2081. I searched on the web but found very little regarding these errors.

Thanks suky

Glyn M Ruck

Those are transmission codes - not to be confused with engine codes

Now we have two of you with Sequentronic problems - hopefully together we can sort this out.

I think it is air in hydraulics or the pump.

https://mbworld.org/forums/c-class-w...ift-gears.html

W203E35

I'm just seeing this. Let me see what I can find out.

W203E35

Let's take a look at these codes.

P2080 - The Pressure in the hydraulic system is too low.
P2081 - Pressure buildup by the hydraulic pump in the system is not possible.


P2080:
-Check hydraulic connection lines to the hydraulic control unit for blockage.
-If there is no blockage in the hydraulic connection lines, then replace the hydraulic pump.
-Replace component B56 (Sprintshift pressure sensor).


P2081:
For this code we have 2 options. We must start up the hydraulic pump and see if it's audible.

Is it Audible?? YES
-Check oil level in system SEQ, adjust to correct level if necessary as specified in repair instructions.
-Check the hydraulic connection lines to the hydraulic control unit for blockage.
-If there is no blockage in the hydraulic connection lines, then replace the hydraulic pump.

Is it Audible? NO
-Check fuse "F58" in component N10/1 (Front SAM control unit with fuse relay module) for tight installation and corrosion.
-Check lines from component N10/1 (Front SAM control unit with fuse relay module) to component M46 (ASG hydraulic pump).
-Replace component M46 (ASG hydraulic pump).

There is also something called a Pressure Reservoir. DAS doesn't mention this but this looks pretty important.

What do you think Glyn?

The errors all have to do with pressure and everything has been changed except this pressure related contraption

sukyb

Thanks Glyn,

Going to see my friend today with the car and will forward this information on, I have had the gearbox pump replaced about 8 months ago when the gearbox completely went, as in not being able to select auto or manual, at the same time replaced the relay which worked for a short period of time. Started blowing the transmission fuse in the Front SAM unit, this turned out to be a faulty relay brought new from Mercedes.

More so recently my friends STAR machine was unable to communicate with the control unit hence why a new unit had to be ordered from Germany as they don't stock this part on their shelves.

Now the STAR machine is able to talk to the control unit, the previous posted codes are what it's reporting. That's as far as I have got and will update this thread when I have any new information regarding this issue.

Thanks
Suky

sukyb

Thanks Karo,

Will pass this info on the my friend

Suky

Glyn M Ruck

Karo - the pressure reservior is like the air tank on an air compressor - only in this case for oil under pressure.

vakity

Karo, I totally agree with you

Glyn M Ruck

Yes - This is IMHO definitely a hydraulic problem (may be aggravated by a sensor)

It's air in the system
or pump or pipe or pressure reservoir
or an actuator or similar

Something in the hydraulic system is preventing sufficient build up of pressure. Once all is installed & correct the first task is to bleed all air from the system. I would like to know if that pressure reservoir has a pressure diaphragm in it - can't find a cutaway drawing.

EDIT - the fact that it has a vent connection on it makes me feel that there is an oil to air sprung diaphragm in it which could fail. If it failed totally then I would expect oil to leak out of the vent???? Where does that venting hose go to?

Ah! another edit - That hose goes back to the valve body so it's part of the hydraulic pressure system & not an air vent. So the pressure reservoir must have a pressure valve in it that vents hydraulic fluid back into the pump circuit. Failure of that valve would PREVENT PRESSURE BUILDUP! We might have to replace the pressure reservoir!

Glyn M Ruck

Excuse me thinking out loud - I'm trying to understand this entire system. We are getting close.

W203E35

Yes, we indeed are getting closer. Our friend Vakity including Sukyb almost changed everything. What else is left? The Pressure reservoir. I'll try to see if I can find more info on this.

P.S My damn hamster got loose in the house. I finally found him looool Now I can sit down and do some research.

W203E35

EPC Parts List. Also it seems there is a hydraulic pump and hydraulic unit..hmmm

Glyn M Ruck

I wish Benz would be consistent with Nomenclature. In the WIS they call it a pressure reservoir. In the EPC a pressure accumulator - more correct!

The bulk fluid reservoir they call a tank. Grrrrr!!!!

jcnash

LOOL

Xhale707

Karo what are you using to pull info?

W203E35

I'm using pdf creator (open source). I hit print and it prints it to pdf instead of paper.

http://www.pdfforge.org/

sukyb

Hi,

Thought I'd post an update, today my friend is checking the hydraulic line for blockages, replacing hydraulic pump and sensor, will know in a few days if this has resolved my issue, will post when I've driven it for a few days to see if the error is reported again.

Thanks
Suky

W203E35

Good luck, hope it get's fixed. Did you read Vakity's thread? He fixed his SEQ transmission.

sukyb

Hi,

Hydraulic pump was replaced, lines all checked but still having same problem, pressure sensor if this is the one attached to the hydraulic pump then this was also replaced but still no joy. My friend is telling me that it's loosing pressure from somewhere as he can see the pressure dropping on his STAR machine. He's still got the car and tommorrow is going to look into the value body. I know Vakity replaced a pressure sensor is this the one with the hydraulic pump ?

Thanks
Suky

sukyb

Hi,

Thought I'd post an update, no luck as yet, the gearbox sensor was replaced and still no joy, it seems like the only thing left to replace is the valve body, absoutely gutted....

Thanks
Suky

Sue Max

I am just joining in this thread in case it starts again!

I have Sequentronic problem. I realise I seem to be only the third SEQ member on here!

Mine is showing red F sign - TRANSMISS fault but writing no codes. Seems to leap in low gears.

Would Safe mode write codes?

heneriktollumi

Dear Colleagues,
I have my Mercedes Benz 313 OM 646 inline four 16v DOHC that has Semi-automatic transmission.
When i start engine early morning it moves a little and a noise from gearbox comes. It moves and stops, till it can not move, and red light TCO comes out. I try every morning but it cannot move. While i let the engine to warm up for 20 min, the vehicle then moves. I put it to Mercedes they said we replaced some Relay and hydraulic fluid, but nothing change. The i took care of it. I saw that there were air on the system. Hydraulic pump works normaly. I filled with hydraulic oil bleed all air and it began to move on. But my problem is that now TCO light comes rarely and when it comes the Transmission can not change gears. So every time TCO comes transmission fail. I have to turn off ignition key, to start it again and to move one. This car has a tachometer installed. My question is does the Sensor of tachometer that is installed on gear box cause my problem. Because every time it flash up the gear box cannot change gears. Thank you for your help

Sue Max

This is very similar to the problem I have with mine! NO tachograph on mine.

You have had more work done than I have (relay etc), but sounds like we have the same fault. Mine only did it when cold and just leaving home, but the car is just not trustworthy. I worry it will do it to me miles from home after a long meeting or something.