View Full Version : P0715 Fault Code, Transmission Control Module?

06-06-2015, 11:08 PM
Hi all. I haven't been on the forum for awhile as my 2005 Sprinter 118 has been relegated to occasional driver use.

I'm planning to take the van on a long road trip in a couple of weeks, so I've been driving it more than usual the past few days. Unfortunately, it threw a few fault codes according to my Scan Gauge II: P0715, P0673, and P0380. I believe the last two are associated with the glow plugs, so I'm not particularly concerned about them. However, the P0715 fault "input shaft speed sensor" seems to be associated with transmission issues, which can be a big deal on the road.

On rare occasions the van has gotten "stuck" in gear, but pulling over, turning the key off, waiting for a few minutes, and re-starting has always solved the problem. Those intermittent problems are described here (http://sprinter-source.com/forum/showthread.php?t=28143) but those issues never resulted in a fault code.

I read some posts about the P0715 fault being generated responsive to low voltage to the transmission, so I started by measuring voltages on the (round) transmission connector plug on the right side of the transmission. All of the pins showed 4-6V, which didn't seem good.

I have read numerous posts about transmission fluid wicking up the transmission connector wires to the Transmission Control Module (TCM), so i suspected the same thing might be happening to my van. After removing the driver's seat and disconnecting the TCM connectors, I didn't see any sign of transmission fluid on the connectors or TCM. Just to be sure, I pried the TCM open and the circuit board appeared to be completely dry.

I measured 12V input to the TCM at pin 29. On the output side, the pins measure 4-6V, which corresponds to the measurements I took at the transmission connector plug.

Does anyone know what the voltage output from the TCM to the transmission should be?

It looks like this question was posed previously here (http://sprinter-source.com/forum/showthread.php?t=17365&highlight=P0715)but not answered.

keywords: TCM, TCU, transmission control module, transmission control unit

06-07-2015, 12:52 AM
Additional info. . .

I thought it might be useful to provide specific voltage readings on the various connector pins. All measurements taken with key ON unless otherwise indicated.

TCM Input Connector
01 ==> 0V
29 ==> 12.1V
30 ==> 0.2ohms to GND key OFF, 1ohm to GND key ON then blue relay clicks and 0.2ohm to GND

TCM Output
12 ==> 6.0V
13 ==> 6.1V
14 ==> 4V
15 ==> 4V
16 ==> 4V
17 ==> 3.6V
33 ==> 12ohms to GND key ON, 0.2ohm to GND key OFF
34 ==> 5V
35 ==> 6V
36 ==> 4V
37 ==> 4V
38 ==> 3.8V
L ==> 2.6V
H ==> 3.1V

I also cleaned the GND point contacts at the bottom of the seat base and added a serrated washer.

I'll probably order a new blue relay (A 002 542 25 19, Mopar 05103551AA) as some clicking noises seem to indicate it might be a little flaky and it's probably a $10-20 part.

Any thoughts are appreciated.

06-08-2015, 12:43 AM
Update. . . .

I decided to perform Doktor A's procedure for cleaning the (2) circuit board mounted speed sensors as described here (http://sprinter-source.com/forum/showthread.php?t=2476).

My speed sensors (and the entire transmission interior for that matter) were very clean, so it seems unlikely that the speed sensors are the root cause of my P0715 fault code. I feel better having checked that, but wiggling around under my Sprinter isn't my preferred way to spend a Sunday afternoon.

I did not replace the transmission electrical outlet but will do that this week. The old one doesn't appear to be leaking, but it's an inexpensive part.

I re-installed the transmission control module and driver's seat and will drive it around the neighborhood a bit so I can check the transmission fluid level.

Any thoughts are appreciated. . . . .

06-08-2015, 02:06 AM
Sigh. Test drives around the block did not go well.

On initial startup, my ScanGauge-II indicated fault codes U0101 and P0000. Searching the forum archives, U0101 translates to "lost communication with TCM" and P000 translates to the mysterious "no diagnostic code available".

I cleared the fault codes and shifted into Drive. Shifting was very clunky. The van wouldn't upshift out of 2nd and no tiptronic. It shifted into Park, Neutral, and Reverse fine though.

I stopped, turned off the engine, waited a minute, and restarted. This generated fault code P0702, which translates into "faulty TCM; TCM harness open/shorted; TCM poor connection". The brake pad wear light also flashed on briefly.

I cleared the fault code and took another drive around the block but experienced the same stuck in 2nd issue. I stopped a few times, turned the engine off, and re-started but no change.

I'm assuming the engine is stuck in a permanent limp home mode (LHM) now that will take one of the fancy professional readers to reset. Hopefully that will provide a more specific picture as to the root cause of this problem.

06-08-2015, 05:06 AM
I went out to dinner to take a break from the Sprinter for an hour or so. When I came back I made some quick checks/observations.

First, the blue relay (located under the driver's seat) feeding the transmission control module seems to be running hotter than the surrounding yellow relays. I have no idea whether that's normal.

Second, I removed the electrical connector plug from the transmission and measured voltages on the pins. This was easier to do than removing the driver's seat to access the transmission control module connectors. The transmission connector pins showed 4-6V (I think there might have been on 0V pin which was probably GND), which is what I noted in my original post. So probably no change there.

It seems kind of odd that nobody has posted anything in this thread.......

Aqua Puttana
06-08-2015, 11:11 AM

It seems kind of odd that nobody has posted anything in this thread.......
You've been doing fine by yourself.

It sounds like maybe the TCM electrical connector didn't get seated well enough when re-installed. That can cause the symptoms you describe on your test drive.

If you are stuck in 2nd gear/reverse only LHM then to restore normal operation you will need a fancy scan tool to communicate with the TCM.

Have you checked the TCM connector under the driver seat for transmission fluid contamination?


06-08-2015, 04:01 PM
It sounds like maybe the TCM electrical connector didn't get seated well enough when re-installed. That can cause the symptoms you describe on your test drive.

If you are stuck in 2nd gear/reverse only LHM then to restore normal operation you will need a fancy scan tool to communicate with the TCM.

Have you checked the TCM connector under the driver seat for transmission fluid contamination?

Thanks Vic. I was feeling lonely :laughing:

I'll double check that the TCM connectors on the TCM module are fully seated. The voltage readings I took at the transmission seem to indicate that the connectors are okay, but removing the driver's seat only takes a few minutes.

Transmission fluid contamination of the TCM connector/module was the first thing I suspected, but everything was dry and clean. I even pulled pulled the module apart to verify that the circuit board was dry.

I measured 12V input to the TCM at pin 29, but TCM output is no more than 6V. Is this normal? I read a few posts indicating that TCM output voltage should be 12V.

06-09-2015, 12:35 AM
Update. . . .

I have an appointment at Rob's Transmission Shop in Issaquah, WA for Wednesday morning. I'll probably just use my AAA tow coverage to have it dropped off there. They have Sprinter experience and have the required fancy diagnostic computer.

06-11-2015, 01:58 AM
Update. . .

Rob at Rob's Transmission cleared the codes and the van re-set to normal operation. It was a little low on transmission fluid, which wasn't unexpected given I drained the fluid. He topped it up, drove it a bit, and everything seems to be working fine with no fault codes. I'll make it my primary vehicle for the next few days to see if it throws any fault codes again.

Apparently Rob has done a fair bit of Sprinter transmission work, so I asked him what types of failure modes he's seen. He said he's *never* seen the TCM wiring harness wicking problem, but was aware of it and it's something he checks for. He's replaced several of the connector boards and indicated that he has seen a few solenoid problems. He indicated that failure of heavy mechanical transmission bits (gears, bearings, etc.) is rare. He doesn't like how picky the transmission is about fluid level and how difficult it is to check that, and thinks that's a major design flaw - - - which I'm sure most of us would agree with.

06-12-2015, 02:09 PM
I drove the van about 20 miles yesterday. A couple of blocks away from home going up a small hill, I noticed that it seemed like the transmission hadn't downshifted. I tried changing gears in tiptronic mode, but it remained in Drive. The check engine light (CEL) wasn't triggered.

This has happened a few times randomly over my 80k miles of ownership. So as in the past, I pulled over, turned off the engine for a minute, re-started, and the truck shifted normally.

I'll continue to drive it over the weekend in hopes of generating sufficient fault codes to isolate the problem. It seems like the most likely culprits are the transmission control module (TCM) or the connector plate/board inside the transmission.

Aqua Puttana
06-12-2015, 02:34 PM
Is the TCM output pin still 6 volts?

Update. . .

... He doesn't like how picky the transmission is about fluid level and how difficult it is to check that, and thinks that's a major design flaw - - - which I'm sure most of us would agree with.
Not that anyone asked...
If he's referring to transmission temperature information MB claims is necessary, then that is a pain in the a$$, but there is a simple solution.

This may save someone the expense of a dealer visit, or the effort needed to obtain the transmission temperature. It is also posted in my Stoopid Things thread.

”HOT” Check the Transmission Fluid Level without Temperature Readings

Mercedes Benz recommends knowing the transmission temperature reading before checking the fluid level. The transmission temperature information is not readily available to most people. There have been many discussions about how the transmission level should be checked. My opinion is that an "in the range" fluid level reading is safely obtained by getting the engine and transmission "HOT" like most all other vehicle manufacturers specify in their operator manuals.

Background information follows. You may skip down to my procedure below if you don't want to bother with my copied, pasted, and modified ramblings.
Everyone who owned a Detroit iron vehicle has been checking their transmission fluid level using the operator manual instructions since they began to care. Never did you see anything but "Hot" so nobody questioned that there might be an important associated critical level change which required graphing fluid height vs temperature. And there isn't a critical level change when the transmission is "hot".

JD's question about checking the level cold made me more aware of that. The delta T (change in temperature) at ambient can range in my area from -10F to 95F depending upon the season. A normal "hot" Sprinter transmission around the 180F engine temperature mark (which mine hangs around under normal driving conditions) has a much tighter delta T. That, and making certain the transmission fluid is distributed properly in the operating transmission, is why transmission fluid is measured idling "hot" with the transmission typically having first been shifted to reverse, forward and then back into neutral or park.

Discussions on the forum indicate that the Sprinter transmission temperature in typical normal operation runs within 10F range of the engine coolant temperature. Thanks mostly goes to TH43 for that info. As I show below, in the "Hot" range that is a 2.5 mm or less than 1/8" possible dipstick level error.

Here's a chart that Dick Autostaretx was so kind to provide. If you look at the possible measuring error at 176F as opposed to +/- 10F (around 180F) I think you will see that it is a very small potential error. The change from 170F to 190F (a full 20F delta) is around 5 mm (approx. 3/16"). Please look at 3/16" on a ruler scale to help remind you how little distance that is.


I don't recommend "flying blind". I recommend getting the engine temperature up to the 180F range "HOT" and then checking the transmission fluid level per the procedure.

The MB engineers and marketing people are smart. Smart enough to know that specifying a transmission temperature and having an associated graph is good business.

Let's see... If we put out a tight temperature specification (which can only be read by our sophisticated scan tool) for transmission level testing then the customer will need to come into the dealership for that service. Oh wait...:doh: if they have a dipstick then they may just wing it. Call production and have them eliminate all transmission dipsticks. Design some sort of red security tab to seal the tube too. That should scare them away from messing with it. Have Helga submit the U-CAN-HELPII cost reduction saving form for dipstick elimination. Inform the dealerships we found a way to increase repeat business by having them come in for the fluid level checks. :dripsarcasm::dripsarcasm:

If one is concerned about getting the transmission fluid level up to the top of the range then an ambient temperature of 60F to maybe 75F "Hot Test" should be ideal. For those willing to be happy with being somewhere within the range then the ambient becomes less critical. Remember, 20F delta is only 3/16" error.

I can't argue that, if you possess the means, the best way is to access the temperature. That said, a "Hot Test" is better than no test at all.
For those interested more discussion and detail is provided in this thread.

Should you have any discussion or comments about my "Hot Check" please take it over to that thread.


HOT Check Procedure

Take your Sprinter for a drive until the engine temperature has been operating at around 180F for a time. That will assure that the drivetrain is up to a "Hot" operating range. Find a level area to park. You can then follow the MB transmission fluid level test instructions.

This method will also work in lieu of the MB instructions.

After warming as described above, idle your engine for a bit. Don't shutdown the engine. Without actually moving the vehicle shift into reverse for a bit, into drive for a bit and then back to Park. This assures that the fluid is distributed in the various sections and passages. Check your transmission level while the engine is running. If you are within the acceptable 176F Hi/Low (Max/Min) range on the dipstick then replace the dipstick cap (after over 80,000 Sprinter miles I know that the red seal is not necessary) and close the hood. If you think that the level needs to be at exactly the tip top then you should acquire the temperature information. FWIW. vic

DIY dipstick reading tip: A DIY dipstick may not show fluid level as clearly as the OEM $$$ unit. I find that if I wipe the stick well immediately before inserting it into the dipstick tube, carefully draw it out, and then press the end flat against a flat piece of paper towel the fluid is easily read by what wicks onto the paper towel. I also find that after filling the transmission via the dipstick tube it is best to wait for quite some time before doing a level check. Otherwise the fluid hanging in the inside of the tube gets on the DIY dipstick as it is pushed in which makes seeing the level on the stick more difficult.

This is one type factory style dipstick.


If you accept the "Hot Check" theory then it is no different than most other transmissions.


06-12-2015, 11:18 PM
Is the TCM output pin still 6 volts?

See here (http://sprinter-source.com/forum/showthread.php?t=17365)for a discussion of TCM output voltage. I haven't checked my connector, but I'm pretty sure that output voltage doesn't register as 12-volts on a voltmeter.

06-15-2015, 05:11 PM
After driving the van for a few days, I dropped it off at the transmission shop again so they could check the fault codes.

Based on the fault codes (speed sensors), they say the problem could be the connector plate or the transmission control module. And that they can't isolate which one is the problem (even with the fancy diagnostic computer), although based on their experience, they think the connector plate is the most likely culprit.

So I'll be taking a backup vehicle on my roadtrip this week. When I get back I'll order a connector plate, swap that out, and see how things go from there.

07-08-2015, 02:36 AM
Any updates?

07-08-2015, 01:30 PM
Anytime time there is a transmission code or codes that indicate that there is a speed sensor fault and the transmission does not slip the most likely culprit is the conductor plate (connector plate). When looking at the speed sensor values in the SDS you can watch the fault by seeing the speed change to 20000 RPM This is a fault value. The connector at the transmission when sitting with the key on and engine off should read 4-6 volts on the sensor and solenoid pins (mostly all) This is because the temp sensor, speed sensor, range sensor all are sensors and only require 4-6 volts to supply info back to the TCM (EGS). The other set of voltages are for the solenoid supply circuits, which by the way are PWM (pulse width modulated) and low current solenoids. The only way to watch those voltages change would be to drive the van with a Scope on the passenger seat connected inline with the solenoid supply circuits and watch the the changes in the digital patterns. There are resistance checks that can be performed at the trans connector for the solenoids (which at this time I can't remember what the resistance is supposed to be for each one, that info is in the SDS for guided testing). I feel that replacing the conductor plate will in fact rectify the situation.

P.S. Don't take the module apart unless you see the signs of fluid in the module connector, or plan to replace the module. remember that electro-static discharge (ESD) is one of the largest killers of circuitry.


11-12-2015, 02:18 PM
I haven't had any more issues since replacing the connector plate, although I haven't put very many miles on the van since then.