Carl_

I will further check it out, probably tomorrow and also with there new and the old TCM.
Your videos has also been a great help, thank you very much.
Regards, Carl

jjrichar

After looking at your symptoms, I'm pretty convinced your distance sensor is faulty.

The TCM will only detect a distance sensor fault giving a code of 1731-1738 if the duty factor response from a channel is outside the range of 10-90%. If it stays inside this, then it assumes the distance sensor is working OK and it gives other errors due to these indications being sensed as another type of fault, in this case as a gear selection fault.

With channel 1 seemingly giving good indications at times, but not always, the incorrect DF seen at times has been perceived as a gear selection fault. There is clearly a problem with the sensor if it's giving a 60% DF return with no magnet near as good sensor will always read 95% with no magnet detected. It will detect an OEM magnet when within about 5cm of the sensor from my experience. If the sensor is removed from the transmission and tested in isolation well away from a magnetic field and you get a 60% return it has failed.

Other types of failures like this have been reported before. For example, a low 5V input supply error would normally be considered a TCU problem, but on most occasions it's actually a distance sensor fault that is dragging down the voltage. People chase their tails trying to rectify the 5V supply, but as soon as they change the distance sensor the problem is immediately eliminated.

Also, can you give me some feedback on the 911 video I recently posted? Your car being a 991 C4 is about as complicated as it gets. Some of the procedures in the video were speculative based on the workshop manual and some educated guess work. You clearly got the rear casing off with the transmission remaining in the car which is great. I'm just interested in how much of the procedure I posted wasn't right on the mark. Thanks

Carl_

Currently I lack the time to investigate the car further. One certainty is that there is 1 sensor stuck at 60% duty-cycle without a magnet nearby and this with both the old and new TCM. Very peculiar that the duty-cycle of this sensor does respond to a magnet and this with values between 10% and 90%.

It would be my pleasure to assist you with additional info regarding the work done on this 991.1 C4 to supplement your manual. Regards, Carl

john007

My Porsche 981 boxster S 2014 has been sitting for about 2 years now with very similar issue like everyone here without any solution so far for me. I just stumble onto this thread and hope someone can get me going again. The vehicle throws out the instrument cluster "start/ stop operation deactivated", "Transm. fault Poss. no R gear Drive on poss.", when i shift to drive the cluster will go directly into gear 2 or sometimes will blink R. I plug in a launcher x431 scanner and the code that comes out is "P0843 Pressure sensor 1 (Clutch 1) Short circuit to B+ No fault symptom available". I used to be able to turn off the car and start it over it may allow me to drive, but after a few miles happens again. I notice that when I clear the code with the scanner I will always get the code P0843 back when the issue shows up, but sometimes I will see both P0843 and P17B1 clutch 1, implausible control pressure no fault symptom available.

I have a new TCM Module from Porsche in hand and the Shingho Auto refurbished solenoid set I purchase. I installed the Solenoid and got a freelancer programmer to come by to program and he said he was unable to do it and suggested a new TCM to be install and he would come out. So I installed it and got him to come out. Well he said he did it, but for some reason I tried to shift gears and no gears will show up on the instrument cluster. I installed the the old TCM and the instrument cluster shows only get R and not the limp to 2. Do you believe that it was program improperly? I then took the old tcm and solenoid and reinstalled it back in and back to square one. Does anyone know if I can program the solenoid or TCM with a luancher x431, autel 906, or a snapon Zeus? I would have to move a few mountains to get them again... Or I would need to get a PIWIS to do it? Regardless, I am going to try this weekend to get the pressure regulator current for 1-6 (mV), pressure sensor 1 and 2 value (bar), and distance sensor value from the vehicle on idle. Can someone please help me with the values at idle or what I should expect to see? I saw one posting for the values but it was the values during vehicle damage and not the values of a healthy vehicle. Also, should I be looking at any particular things? To help further diagnosis the problem. I am planning to track the whole process and solution to hopefully help out on this thread because Porsche want to sell a remanufacture transmission which I do not believe is right.

jjrichar

From what I read this seems to be just an intermittent pressure sensor 1 failure. This is the sensor that measures the pressure going to clutch 1. I don't think either a replacement TCM or solenoid set will do anything for you. It make sense that it would only select 2nd gear from a stop with the failure, as gears 2, 4, and 6 are on clutch 2, which is working fine.

To diagnose correctly, you need a diagnostic tool like PIWIS that will give you live readouts of all the transmission parameters. I use PIWIS 2, but others here may be able to give some guidance on other tools that will do the job. I suspect you are getting the pressure sensor 1 fail as things warm, but a live readout of the parameters when you are driving the car will tell you what is going on. For this type of test, you only need to drive it back and forth using 1st and reverse in your driveway to avoid having the failure a long way from home.

stjoh

You can often determine a faulty pressure sensor with just a ohm-meter. Based on the code and symptoms provided that sounds very likely. There is a post earlier in this tread that shows the typical resistance values. Measure values both when cold and hot. You will likely see it fail when warmed up. Like jrichar said, don't waste money and time on solenoids and TCUs, the symptoms clearly point to a pressure sensor issue (or possibly associated wiring). Feel free to send me a PM for more info.

The good news is that these sensors are readily available and not very expensive. You will have to remove the gearbox and the clutch to access though but that is something any decent shop should be able to do.

PWM1972

Hi All,

What an impressive thread.

Today I had a call from the OPC to tell me they have to replace my 2009 Boxster S PDK. In the UK it's an eye watering £15,912 ($19,094). Needless to say, it came back home with a still broken PDK. This thread was my inspiration to give it a go myself. However, the Error Codes I have are not quite the same as those listed in this thread, so I'm hoping for a point in the right direction before buying a T-Design DS only to find it's something entirely different. The gearbox does not make any sounds when trying to select R, D and the Display shows 1 and the red warning is Emergency Transmission Run. There is no drive at all.

I'm fairly handy with a spanner (wrench), so have no issues making the puller to remove the case etc, just need to know what parts I'm likely to have to replace. I did wonder if this is a valve body issue, however, OPC should be able to replace this part so I'm a bit confused.

My Autel MK908 shows the codes are:

PDK(Tiptronic) ( 5 DTCs )
- P17D1 Gear selection hydraulics fault.No or wrong shift rod moved.
- P177C Reverse gear not disengageable
- U0401 Can fault, engine
- U0418 Can fault, brake
- P0841 Pressure sensor 1 measured value implausible

PDK Selector Lever ( 1 DTC )
- P1802 Shift/keylock solenoid position implausible


Thanks in advance.

ss109

There’s likely a root cause that triggered all these. I would clear the codes, start, and see what happens. My money is on the pressure sensor.

PWM1972

I did delete all the code first. This is what came up when I started the car and selected D.

stjoh

Measure the pressure sensor #1 resistance first. You can do that with a regular ohm meter. Without taking a closer look at the codes my instinct tells me this is a pressure sensor issue. Theses are easily available and fairly easy to replace (will require transmission and clutch removal though).

john007

Do you know where I can purchase a pressure sensor switch for the porsche 981 boxster S PDK 7 speed? I assume replace both pressure sensor because I am in there anyways for future sake. Also, when I replace it do i need to calibrate or what is the procedure after replacement?

john007

So, only 2,5,6 gear will show up and when I reverse it will jolt, but here is the full information I got from the scanner for the transmission health with the P0843 code only now after clearing the DTC:

Pressure Regulator Current 1 Actual Value (mA): 47.8
Pressure Regulator Current 2 Actual Value (mA): 48.2
Pressure Regulator Current 3 Actual Value (mA): 849
Pressure Regulator Current 4 Actual Value (mA): 536.6
Pressure Regulator Current 5 Actual Value (mA): 44.8
Pressure Regulator Current 6 Actual Value (mA): 44.0
Pressure Regulator Current 7 Actual Value (mA): 0.0

Pressure Sensor 1 Actual Value (psi): 12.61
Pressure Sensor 2 Actual Value (psi): 23.96
Pressure Sensor 3 Actual Value (psi): 0.00

Ambient Pressure: 1.0156
Input Shift 1 Speed Actual Value (rpm) 371
Input Shift 2 Speed Actual Value (rpm) 146
Engine RPM Actual Value (RPM) :660
Selector - Lever Position: P Position

Distance Sensor 1 Position Actual Value (mm): -0.132
Distance Sensor 2 Position Actual Value (mm): -0.292
Distance Sensor 3 Position Actual Value (mm): 0.070
Distance Sensor 4 Position Actual Value (mm): 0.492

Activation of shift Lock Solenoid Inactive
High sight Switch 1 Actuator Power Supply Actual Value ((V): 12.78
High sight Switch 2 Actuator Power Supply Actual Value ((V): 12.73
High sight Switch 3 Actuator Power Supply Actual Value ((V):12.75
High sight Switch 4 Actuator Power Supply Actual Value ((V): 12.89

Activation of Terminal 15: On
Activation of Accelerator Pedal Position (%)

I am not sure if the Porsche 981 has a "pressure sensor 3" and a "Pressure regulator current 7"? I am using borrowing a snapon Zeus scanner maybe it is generic info? I read in one of the threads 1270 similar code and 1280 with there vehicle which eventually was a pressure sensor switch there pressure regulator current was 0.0 and pressure switch 1 was 0.0 but they had three pressure sensor switch? Base on the scan information any suggestion what to do next would help alot or any other scan information do you guys need?

glennvdb

Well, finally I got the courage the measure the signals. Results below ...

I observe 2 potential issues:
1) The channel 1 signal quality is not as good as the others. It seems to be less square, suffering a bit of too much capacitive load
2) In R, channel 4 shows 87% duty cycle, and not the expected 75-80%

Any other opinions based on this data?

Thanks in advance!

It appear the probes of my oscilloscope required a tuning of its filters. Going to redo the tests with the probes set correctly and I'll update the graphs asap!


Gear lever in P

Gear lever in R

Gear lever in N

Gear lever in D

PWM1972

Autel can’t display the reading of an individual sensor ( or I can’t find it anyway)

I have PIWIS 3 coming in a few days. I will see what reading I get for the Pressure Sensor and other readings like DS and Valve Body.

Hopefully a full diagnosis will mean i can do a full fix the first time around.

stjoh

That's all good but you should try to disconnect the front connector and measure the resistance on the pressure sensors using a standard ohm-meter. This could tell you if there is an issue with a pressure sensor in many cases. You should see around 8 kOhm, please post your measurements.

pressure sensor 1 (B30 to B3)
pressure sensor 2 (B31 to B3)