I am getting Code P0705

Tiny
JITHIN MATHEW
  • MEMBER
  • 2011 MERCEDES BENZ C300
  • 3.0L
  • V6
  • 4WD
  • AUTOMATIC
  • 77,800 MILES
I am getting this code on my car. The car does not go into limp mode and shifts perfectly fine into all 7 gears without any issue. I scanned the car at Mercedes and they said it needs a new conductor plate and new fluid and filter. I took it to a different authorized German car shop and he said the car doesn’t need that as it shifts fine. He recommended me to change the fluid and filter. What could be the issue? Does this thing have a gear shift module beneath the gear shifter that’s causing the problem?
Tuesday, February 4th, 2020 AT 6:50 PM

18 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,053 POSTS
Hi,

I looked up the code and it is related to the transmission range sensor. Are there any faults you have noticed? The range sensor is what determines the gear selection.

Joe
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Tuesday, February 4th, 2020 AT 8:02 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 64 POSTS
No, I don’t see any faults. The car throws this code and turns the check engine light on. The car confused itself and went into neutral twice.
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Tuesday, February 4th, 2020 AT 8:34 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,053 POSTS
When that happens (neutral) pay attention to see if the gear indicator is showing drive and not neutral. The range sensor can cause this type of issue.

Let me know.
Joe
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Tuesday, February 4th, 2020 AT 8:43 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 64 POSTS
The car shows drive but I know the car is in neutral because I might be going 60 mph and the car would just rev for a second and then go back into gear. This only happens rarely and can’t tell exactly when will it happen again. Do you know where the range sensor is located?
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Tuesday, February 4th, 2020 AT 8:51 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,053 POSTS
This vehicle has a fully integrated transmission control unit. It is in the transmission. It isn't something you want to try and find it isn't the problem. It isn't cheap. I attached a pic of it.
Image (Click to make bigger)
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Wednesday, February 5th, 2020 AT 8:41 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 64 POSTS
I don’t think the conductor plate is defective. I have seen other Mercedes with a conductor plate issue where the car would go into limp mode and won’t go higher than second gear. My car shifts fine into all 7 gears it has and doesn’t go into limp mode. It just throws the code and turns the check engine light on. I’m not sure if a bad trans fluid would cause this issue.
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Wednesday, February 5th, 2020 AT 8:51 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,053 POSTS
The idea that it jumps to neutral is certainly a concern and understand why you want it repaired. I have a feeling it could be related to the sensor I mentioned or even the the control module. Both of these will require extensive diagnostics.

Joe
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Wednesday, February 5th, 2020 AT 9:08 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 64 POSTS
Can a bad fluid and filter cause this code? I haven’t replaced the fluid at all and the car has close to 80,000 miles on it.
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Thursday, February 6th, 2020 AT 5:58 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,053 POSTS
Hi,

The manufacturer recommends 40,000 miles or 4 years for intervals. So, it certainly is past due. It wouldn't hurt to try it since it needs done regardless. Will it fix the issue, if the filter is partially plugged, it could.

Let me know what you decide.

Joe
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Thursday, February 6th, 2020 AT 6:20 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 64 POSTS
I will try to replace the fluid and filter. Today when I started in the evening, the car turned the check engine light off by itself.
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Thursday, February 6th, 2020 AT 7:29 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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I think that is a good idea to service it. Interestingly, for the light to have turned off, it seems to have completed a drive cycle and saw no issues. Try the fluid change and let me know what happens.

Take care,
Joe
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Thursday, February 6th, 2020 AT 7:39 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 64 POSTS
I am currently replacing the transmission fluid and filter. My technician took out the solenoid that the car was saying is defective. He said there is nothing wrong with the solenoid and it’s functioning properly. He’s telling me the conductor plate might be defective but told me to wait before replacing that. I don’t think it’s the TCM as the car never went into limp mode and it shifts into all its gears fine.
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Friday, February 14th, 2020 AT 6:12 PM
Tiny
JACOBANDNICKOLAS
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I agree with you and feel that is a good idea. Let me know the results. Hopefully, that will remedy the issue.

Take care and I'll watch for the results.

Joe
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-3
Friday, February 14th, 2020 AT 7:55 PM
Tiny
DANIEL CHAVEZ
  • MEMBER
  • 4 POSTS
Hy did you fix the code? I'm currently have the same code p0705.
I kind of want to replace the conductor plate
in case you did that, did you have to reprogram it?
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Friday, February 28th, 2025 AT 10:58 AM
Tiny
DANIEL CHAVEZ
  • MEMBER
  • 4 POSTS
Hey did you fix it?
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Friday, February 28th, 2025 AT 11:14 AM
Tiny
JITHIN MATHEW
  • MEMBER
  • 64 POSTS
Hello Daniel,

I fixed the code 30,000 miles ago and the car is going great. The code is set because the speed sensor built into the tcm has failed. Only way to fix it is by replacing the tcm and having it reprogrammed with Mercedes xentry. I gave it to a Mercedes independent shop to do it. After the new one was installed my car wouldn’t accept the new programming, so the independent shop towed my car to a Mercedes dealership, and they figured it out.
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Friday, February 28th, 2025 AT 5:56 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Thank you for the update on the repair. It is appreciated and I'm sure others will benefit from your reply.

Take care,

joe
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Friday, February 28th, 2025 AT 9:25 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 64 POSTS
No problem. Let me know how your repair goes.
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Saturday, March 1st, 2025 AT 1:16 PM

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