Limp mode problems

[Stitcho82]

Hi, I know this has been posted loads but I’ve not managed to find an answer so far. My 2005 C220 Aventgarde is stuck in limp mode with a P0730 error code. Stuck in 2nd and it slams into drive and reverse.

Took it to a gearbox specialist and checked that there were no leaks, etc and everything checked out ok. They got the 730 error but said they had never seen it before so couldn’t help. I know it’s only a generic message though. I’ve got a friend lending me a STAR kit next week to get the detailed error codes but I’m wondering what else it could be.

It first happened when I had my space saver on my rear passenger side (cracked alloy in 3 places that took a while to get repaired) for a while so the gearbox garage said it might be a faulty ABS sensor on that wheel. I’ve now replaced that sensor (that was a pain in itself) and still have the problem.

I’ve got an OBDII reader which when plugged in comes up with the P0730 error which I can clear but as soon as I start the car it comes back again. Someone suggested it’s a short somewhere but I don’t even know where to start looking for that. I’ve got access to multimeter so I can test the electrics but don’t know what to test and where.

I’ve also tried the TCM reset process to no avail. I am also getting an ESP fault on my dash but don’t know if that’s related. The garage said I had a load of other error codes (which they didn’t give me) but they were to do with heater controls and my cruise control. Nothing really related to transmission.

Thanks in advance for any help or suggestions what to attack next.

 

[Tuercas viejas]

Here is some generic info on that problem you are experiencing

0730 code definition
The P0730 code identifies a problem within an automatic transmission. The P0730 code is often associated with the P0729, P0731, P0732, P0733, P0734, P0735, and P0736 trouble codes.

What the P0730 code means​

P0730 is the OBD-II generic code for an incorrect gear ratio detected in an automatic transmission. The ratio of a combination of engine speed and throttle position and the speed of the transmission is used to determine what gear the transmission will use when driving. If there is a problem with any gear within the transmission, then the P0730 code will appear once this ratio is calculated from the sensor data in the transmission.

What causes the P0730 code?​

The incorrect gear ratio code may have several causes:

• Bad or dirty fluid in the transmission
• Low fluid in the transmission
• Broken mechanical components within transmission
• Internal blockage in fluid lines
• Bad transmission control module
• Problem with the torque converter clutch
• Problem with the shift solenoids

What are the symptoms of the P0730 code?​

Eventually, the P0730 code will cause the Check Engine Light to illuminate on the dashboard. Along with this indicator, there may also be slipping within the transmission and poor overall transmission performance. The transmission may stay in a low gear for too long, or stay in a high gear until the engine stalls. Fuel economy may worsen as well.

How does a mechanic diagnose the P0730 code?​

Prior to further diagnostic tests, the fluid in the transmission should be checked for quality, and the level of fluid should be noted. Old or dirty fluid should be replaced.
The P0730 code is diagnosed with an OBD-II scanner in the hands of a qualified technician. This will provide them with the necessary information from the engine that they can view in real-time. The code will be cleared and the mechanic will take the car for a test drive. If the code comes back, then the code was caused by an actual problem in the transmission.
Depending on the severity of the issue, the technician may perform a torque converter stall speed test to determine if the engine stall speed is within factory specifications. The engine speed must match the readings from the transmission sensor.

Always remember the MB transmission system relies on the right rear wheel speed sensor to receive an output speed signal. A road test in live data from a scan tool will usually show up what is wrong.

Common mistakes when diagnosing the P0730 code​

The biggest problem that pops up when diagnosing the P0730 trouble code is that the symptoms may all be stemming from low or dirty transmission fluid. Topping off or replacing this fluid may solve all of the issues in the transmission triggering the trouble code.

How serious is the P0730 code?​

The severity of P0730 code depends mostly on the application. In some cases, minor issues can trigger the code, due to the fact that any abnormality in the transmission speed will trigger it in any gear. It could also be triggered when there is a major problem with the transmission, rendering it unable to change gear, though it would likely be accompanied by other, more specific trouble codes.
When the P0730 code appears it is best to have it diagnose by a qualified technician. In many cases, the problem goes away as soon as the code is reset once, especially in cases where the Check Engine light appeared immediately upon startup.

What repairs can fix the P0730 code?​

The most common repairs to address the P0730 code are as follows:

• Inspect electrical connections and wires connecting sensors to the transmission control module.
• Repair or replace any corroded or damaged wires in and around the transmission control module.
• If the transmission fluid and wiring is all in working condition, then components in the transmission itself may need to be repaired or replaced.
• If there is a problem with the pump, shift solenoids, or torque converter, then the transmission will have to be removed for the repairs to take place.
• Once the necessary repairs are made, the transmission must be replaced and inspected before being tested to ensure that it works without any trouble codes, including the P0730 code.

Additional comments for consideration regarding the P0730 code​

If the Check Engine Light comes on because of the P0730 trouble code right when the vehicle starts, then it can probably be fixed by simply resetting the code. Small problems with the wiring, common in aging vehicles, can easily trigger certain trouble codes without the presence of a serious problem. When the P0730 code appears, it often does so alongside several other error codes.t

​

Tuercas viejas

 

[Stitcho82]

Thanks for all the info Tuercas, probably the most I’ve found in all the months of searching.

So, I’ve been to see my mate today with the proper diagnostic kit and I’ve managed to get the proper codes. He cleared the codes for me and hey presto I’m out of limp mode, but for how long I don’t know. These are the codes I got:

Transmission
P2503
P220A
P2401

Engine
11664
2632
2232

Could anyone possibly shed any light on these codes and what I am looking for. A quick google makes me think it’s the 2232 engine code that’s causing the problem but I may be wrong.

Thanks

 

[Petrol Pete]

Hi Stitch , not sure why today is the first time I have seen your post dated 3rd April, but hey ho TV got there first and he is the man.

No where do you mention giving the transmission a full ATF (including T/C ) and filter change along with a new TCU plug . This has been done ...right ?

 

[Stitcho82]

So I took it into a gearbox specialist garage who did all the checks for fluid levels, leaks, etc but the filter and TCU plug wasn't changed as they said it looks like it had been done recently (I would say at least a year ago as I've only had the car since September).

That being said they proclaim to work on these transmissions all the time but had never seen a P0730 code before, so who knows.

 

[Petrol Pete]

Very odd, this is a common transmission used all over the world in all sorts of cars , trucks etc in one form or another and as a result there is a vast amount of aftermarket parts and knowledge available.

Checking the fluid level is one thing , but understanding what condition it is in is another thing , but if they are specialists they will know that. If it were mine I would change the fluid and the filter and try again. Much cheaper than getting the box replaced

 

[Stitcho82]

Thanks Pete. They initially thought it was the fluid or a leak but they said it all looked in good condition. My friend who had the diagnostic kit has recommended another gearbox specialist in Chester who he uses all the time so I might give them a bell and see if they can do the fluid change (normal garages around here won't touch it).

 

[W1ghty]

Thanks Pete. They initially thought it was the fluid or a leak but they said it all looked in good condition. My friend who had the diagnostic kit has recommended another gearbox specialist in Chester who he uses all the time so I might give them a bell and see if they can do the fluid change (normal garages around here won't touch it).

There must be an MB specialist up your way , member @SmartAmg might be able to recommend one

 

[SmartAmg]

There must be an MB specialist up your way , member @SmartAmg might be able to recommend one

I use SDC Mercedes indie, in St Helens.

 

[W1ghty]

I use SDC Mercedes indie, in St Helens.

It might mean the op travelling to “woolly back” country but might be worth it for the MB specialist to check out his box

 

[Stitcho82]

Thanks for the recommendations, I know there is a specialist in Speke but would rather go to someone recommended.

So bit of an update, I’ve just taken the car out and it was absolutely fine (gear changes were a bit clunky). Drove 10mins down the road to my friends and parked up but didn’t switch the car off. Got out opened the boot to let the dog in and then got back in. In the space of stopping for less than 5mins it had gone back into limp mode again.

 

[Stitcho82]

Now I’m even more baffled. Drove the dog to where we walk him in limp mode and parked up. Got back to the car a while later, pulled off and no limp mode. Got back to my friends, parked up outside (didn’t switch the car off again), let the dog out and what do you know, back into limp. Drove down the road a bit, pulled up, switched the engine off, waited about a minute and started it again, hey presto no limp mode.

I am at a complete loss now. There are loads of speed bumps by my friends so I was wondering whether something is getting knocked when I go over them. Also when I came round the corner to my friends and tried to pull away from a junction there was virtually no power in 1st.

 

[Petrol Pete]

OP , Sometimes switching the car off an back on again will take it out of limp mode for a bit but you obviously have an ongoing fault . what I am struggling to understand is the fact that everyone who has looked at your car so far tell you that it is beyond them to service /diagnose it.

The full service is something members on here have done DIY and many owners worldwide do the same . I do not expect you to DIY it , but the fact that the job can be done on the average driveway with a decent set of tools beg's the question ..who have you been speaking to about the job.

A full service cost between £275 and £350 , depending on where about you are in the UK. I hope the company in Chester comes up with the goods.

keep on here and let us know how you are getting on

 

[Stitcho82]

Thanks Pete. I’m more than happy to do the work on the car myself, I’ve got all the tools I need and I’m no stranger to getting dirty under the hood. Only reason I haven’t done it myself is that I was told that it couldn’t be done at home because it needs to be done electronically (or something along those lines with a computer hooked up). Had an RAC mechanic and the gearbox garage tell me (although they are probably biased).

Im not bothered about getting it done at a garage and I think I was quoted about £250 to do it but if I can do it from home then I’m happy to give that a go.

 

[Tuercas viejas]

Well certainly have a go!
From the fault codes you have posted these might be useful then again not, as MB tends to have slightly different fault codes than the generic used by the mainstream brands !
P2503 Charging system low
P220A Nox supply voltage low
P2401 Emission controls low voltage.
P2623 Injector control pressure voltage low
'P2232 O2 sensor control circuit fault .

On the face of it there seems to be a threshold voltage supply issue in the car that caused it to start shutting down.
Something like the ASD relay or a sudden strong parasitic draw.
The same would start throwing transmissions faults & confusing everyone who looked it and not as a glitch that took place & has been cleared
Hope that helps
Tuercas Viejas

 

[Petrol Pete]

Stitcho A full (febi) kit is available here in the UK from SPRAUTOS.COM around £300 including a new conductor plate . other suppliers are available. Don't buy anything until you are sure you need it TV ^^^^ is giving good advice .

 

[Stitcho82]

Thanks Tuercas and Pete. I’ve had a feeling that it may be electrical related as when I had the OBD hooked up I could clear the P0730 code but as soon as I started the car it would come me back which makes it look like a short or something.

Electrics aren’t really my thing but I’ve got access to a multimeter for testing things if I need to, just don’t know where to start.

 

[Stitcho82]

I’m assuming the ASD relay is one of these in the main fuse box? I can’t find any info on it

 

[Tuercas viejas]

Here's some info

Automatic Shutdown (ASD) Relay - Function - Failure - Testing

The function of the automatic shutdown (ASD) relay, is to shut off power to major systems. When the key is turned off, as a safety feature.

dannysengineportal.com

A suggestion
Shoot me a picture of your fuse box and I will try to identify it .
I have most MB diagrams & schematics for NAS spec models but not your UK /Euro platform.
Tuercas viejas
[email protected]

 

[Stitcho82]

Thanks Tuercas, here’s the fuse box. I visually inspected the relays and they all look ok so no water leaks, etc causing problems.