Mercedes E230 Transmission stuck in 2nd gear limp mode

[oklodhi]

Hi

My mercedes e230 (w210) transmission (722.6) is stuck in 2nd gear.

I got it diagnosed on computer and the error was with the circuit plate. The transmission was opened and the sensor on the circuit plate was cracked. The plate was changed but the gears continue to behave abnormally, sometimes shifting and sometimes car remained in neutral / stuck in 2nd gear. The computer was giving error "Target gear not achieved". Valve body was also serviced many times but it did not help.

After many failed attempts for about one month, the whole transmission was changed. The car shifted gears ok for the 1st day and then problems came back. First the gear lever for 4,3,2,1 stopped working. Car shifted properly in D but the gear limitation in 4,3,2,1 did not work. Car behaved as though it was still in D. Now today morning the car is back again in limp mode and would not shift out of 2nd gear.

I am very frustrated now. Any help would be appreciated.

[bravo122]

@xulfiqar

[iftikharmohammad]

Hi bro, The symptoms seems to be of faulty solenoids in the gear box however when you have changed the entire gear box then i believe the problem is related to the ECU. Get that checked.

[Junaid1981]

Get it checked from Mr. Awais ur Rehman (03004427008)
They are expert in Meecedes Benz and they have original Merc Diagnostic

[Xulfiqar]

Your transmission control unit is in failure mode - hence limp home.

remove the access cover for the control units in the engine room and remove the transmission control unit plugs, check if there is oil in there, if you find oil then remove the unit, unclip the board and wash it in circuit board cleaner and let it dry for atleast 4 hours, clean the wiring and replace the adapter socket on the transmission too where the wiring connects to, Only use a genuine updated mercedes benz part for it - it wont leak. - BE VERY CAREFUL WHEN TIGHTENING THAT SMALL SCREW, If you strip the threads you have to buy a new electrics plate.

check fluid with genuine measuring tool when hot only.

reset the TCU and test again.

btw did you replace the transmission from an exact same model?

If you still do not see any shift but you need to run a live test and see what input torque is measured at idle and if the selector position is registering. However if you are seeing the error of target gear not achieved and you mention that the valve body was serviced (which is not actually required in most cases) then its possible the valve body is a bit iffy (most probably a sticky piston or sometimes a bad solenoid too). MB sells a rebuilt valve body or you can shop around for a refurb kit and refresh it yourself. It might also be a failed TCU, I have come across one where a capacitor on it leaked and destroyed the board. It happened due to oil flooding.

The 722.6xx is a fantastic transmission - it is also used in the SLR mercedes - (its that strong)

[Xulfiqar]

you mention that the gear lever position in 4-3-2-1 behaves like D - when you hook up the diagnostics, what do you see in the selected range.

P=P
R=R
N=N
D=D
4=?
3=?
2=?
1=?

The later models did not have this and had a -/+ the valvebody and TCU are not compatible. That is why when you swap a 722.6xx from another model you either build it for your old unit or get the TCU and shifter too.

the selector linkage only moves in 4 places, PRND - the 4321 are electric switch combinations in the selector only, the physical linkage to the transmission remains in D, This fault is also caused by water/liquid spilled on the select lever. You might want to check that too.

[Xulfiqar]

I hope your transmission is not noisy as the early 722.6xx units had a weak K2 (2nd clutch) bearing design (its a bushing) it eats itself if the transmission is starved of oil - (choked filter etc) Once that bearing is gone, your front planetary gears eat themselves, you will also hear the torque convertor impeller rattling. In extreme cases the front housing needle bearing disintegrates and machines away the pump housing too.

The later ones had a roller bearing there but the problem is that the tooth count is different on the planet carriers. So your old one wont work with the new one. Its a cluster eff but a good transmission repairman can sort it out.

[oklodhi]

I hope your transmission is not noisy as the early 722.6xx units had a weak K2 (2nd clutch) bearing design (its a bushing) it eats itself if the transmission is starved of oil - (choked filter etc) Once that bearing is gone, your front planetary gears eat themselves, you will also hear the torque convertor impeller rattling. In extreme cases the front housing needle bearing disintegrates and machines away the pump housing too.

The later ones had a roller bearing there but the problem is that the tooth count is different on the planet carriers. So your old one wont work with the new one. Its a cluster eff but a good transmission repairman can sort it out.

Your transmission control unit is in failure mode - hence limp home.

remove the access cover for the control units in the engine room and remove the transmission control unit plugs, check if there is oil in there, if you find oil then remove the unit, unclip the board and wash it in circuit board cleaner and let it dry for atleast 4 hours, clean the wiring and replace the adapter socket on the transmission too where the wiring connects to, Only use a genuine updated mercedes benz part for it - it wont leak. - BE VERY CAREFUL WHEN TIGHTENING THAT SMALL SCREW, If you strip the threads you have to buy a new electrics plate.

check fluid with genuine measuring tool when hot only.

reset the TCU and test again.

btw did you replace the transmission from an exact same model?

If you still do not see any shift but you need to run a live test and see what input torque is measured at idle and if the selector position is registering. However if you are seeing the error of target gear not achieved and you mention that the valve body was serviced (which is not actually required in most cases) then its possible the valve body is a bit iffy (most probably a sticky piston or sometimes a bad solenoid too). MB sells a rebuilt valve body or you can shop around for a refurb kit and refresh it yourself. It might also be a failed TCU, I have come across one where a capacitor on it leaked and destroyed the board. It happened due to oil flooding.

The 722.6xx is a fantastic transmission - it is also used in the SLR mercedes - (its that strong)

Checked the control units. They all are dry.
Yes the transmission is from the exact same model. While we were waiting the transmission to arrive, tried some other model transmission but it did not work properly.
Fluid level has also been checked with the tool and it is ok. Fluid was changed after the transmission was changed.

There was no spillage on the selector lever area. I drive the car myself all the time and it has been completely dry.

The car ECU will be checked tommorrow. Today the diagnostic kept getting stuck and unable to get a reading. Earlier I got the computer diagnostics from another workshop who claimed that the ECU is a non genuine one....Do not know how much that is true? as I bought the car used and the ECU looks genuine to me at least.
at the moment the scanning is not possible and error occurs of link to car computer. I donot remember the exact wording. Plan is to check the ECU in detail tommorrow and swap another ECU to see any effect on transmission. The ECU has once been repaired by the previous owner few years back.

[SKY_ZeD]

Hi

My mercedes e230 (w210) transmission (722.6) is stuck in 2nd gear.

I got it diagnosed on computer and the error was with the circuit plate. The transmission was opened and the sensor on the circuit plate was cracked. The plate was changed but the gears continue to behave abnormally, sometimes shifting and sometimes car remained in neutral / stuck in 2nd gear. The computer was giving error "Target gear not achieved". Valve body was also serviced many times but it did not help.

After many failed attempts for about one month, the whole transmission was changed. The car shifted gears ok for the 1st day and then problems came back. First the gear lever for 4,3,2,1 stopped working. Car shifted properly in D but the gear limitation in 4,3,2,1 did not work. Car behaved as though it was still in D. Now today morning the car is back again in limp mode and would not shift out of 2nd gear.

I am very frustrated now. Any help would be appreciated.

See Naeem at INH merchanics near Airport..... His contact no 03228855225.

if this does'nt help you ,get a Bimmer :)..

INH MERCANICS Car Repair & Services

[Xulfiqar]

if your diag tool cannot see the TCM on the bus then all bets are off. The only way you can get it to respond is to read/write to it? btw when you say you cannot link to it how did you extract the target gear not achieved error?

Once you get it to connect I would first verify that the selector positions register on the tool, if not then remove the console and check the wiring too. All diag steps come after that.

[oklodhi]

if your diag tool cannot see the TCM on the bus then all bets are off. The only way you can get it to respond is to read/write to it? btw when you say you cannot link to it how did you extract the target gear not achieved error?

Once you get it to connect I would first verify that the selector positions register on the tool, if not then remove the console and check the wiring too. All diag steps come after that.

Earlier the diagnostic tool was able to give the readings. The reading of "target gear not achieved" was obtained earlier. Now the diagnostic tool is unable to read the computer. The diagnostic tool is Auto Boss.

Tried disconnecting the battery and ECU to reset it however nothing happened.

[oklodhi]

In the start the computer was giving error of circuit plate sensor. When the transmission was opened, the sensor on the circuit plate was found to be cracked.
After the circuit plate was replaced, the transmission never became ok.

[oklodhi]

Below is stepwise

1. Car stuck in 2nd gear. diagnostic giving "circuit plate sensor" error
2. Circuit plate, oil, filter etc changed. (sensor on circuit plate found cracked and filter deformed). Car ok for short while
3. Car again stuck in 2nd gear. Diagnostic giving error "target gear not achieved".
4. Valve body serviced completely. same error "target gear not achieved" and car in neutral when in D and sometimes gear is engaged but still stuck in 2nd gear.
5. Diagnostic tool stopped communication with the car
6. Transmission changed. Gear working fine for one day...selector lever not changing the gears manually, car behaves in D when lever in 4,3,2,1
7. Car stuck in 2nd gear. Diagnostic tool not communicating with the car

[Xulfiqar]

the tool should always see the TCU, if it stops communication then most likely the problem is damaged wiring somewhere. Also make sure the K40 module is perfectly OK. It can also cause stupid issues like this.

when the TCU gets no power - the transmission by default design always gets stuck in 2nd gear.

[oklodhi]

The grip of the TCU was faulty and is replaced. Transmission has now started working properly with proper gear shifts.

However, the diagnostic tool is still not connecting with the ECU.

[Xulfiqar]

what tool are you using? I believe the Autoboss can interrogate the EGS module.

The major cause of wiring failure at that area is oil creeping up from the wiring harness. I always recommend to replace (not refresh) that wiring plug adapter on every ATF change. I also make a habit of checking the EGS (TCM) connectors for any trace of oil anytime the engine oil is changed or the engine is looked on.

If you still cannot read from the EGS module then check the cable of the tool where it connects to the car.

[oklodhi]

what tool are you using? I believe the Autoboss can interrogate the EGS module.

The major cause of wiring failure at that area is oil creeping up from the wiring harness. I always recommend to replace (not refresh) that wiring plug adapter on every ATF change. I also make a habit of checking the EGS (TCM) connectors for any trace of oil anytime the engine oil is changed or the engine is looked on.

If you still cannot read from the EGS module then check the cable of the tool where it connects to the car.

When you say Autoboss can interrogate the EGS module, does it mean it can damage it?

[Xulfiqar]

no not damage, interrogation means it can read and write to the EGS module (aka TCU), That is the only way you can get it to reset if your EGS goes to electric failure limp mode (2nd gear only with full line pressure). Interrogation means - the unit handshakes with the EGS and then asks to report the fault log, just like it does to the ME.

Does the autoboss see other modules like BAS, HVAC etc? Im thinking that the 38 pin connector is either dirty or damaged if you say it could see it once but not after. Even a bad EGS module responds unless you see the board burnt out. The pin no.10 is the EGS module line.

I suggest you find someone with an SDS - its a real nice tool and shows live input, actual and used up torque in the transmission and can also log its activity. Its pretty pricey though.

[oklodhi]

The software was connected through a star computer (laptop) and as per the mechanic the software has been updated. All modules like hvac etc are accessible via the diagnostic tool.

However, the gear shifting problem is still there. Now the gear shifts properly but while running the gear goes into neutral on its own. The star computer is giving error "target gear not achieved".

[Xulfiqar]

if you get the target gear not achieved error then it must also be logging the run report, you can also test the shift parameters from star - see what amount of torque the gearbox is handling.

btw - how smooth are the gearshifts - the car should accelerate like a passenger aircraft ready to take-off, meaning the shifts should be seamless and very strong. I beleive you need to check the valve body and replace the overlap valves, 2-3 pressure spring and test the solenoids (they are ratcheting type) - and btw what ATF are you using?