When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Whilst you mention you measured the freq output from the sensor, did you measure the duty factor, as this is what the TCU is using for the distance? It does seem very strange that the distances are all offset like you say. It's an easy conversion algorithm for the diagnostic tool, as 50% DF will equal zero distance.
Here's what I would do.
Measure the sensor outputs at the TCU while it's in gear. First I'd measure with the engine off, as 1st will be selected on channel 3, and all the others shouldn't be engaged. Then I'd start the car and measure in neutral (all should have a DF of close to 50%), and also in D and R. D will select 1st and 2nd, and R will only select R. This can all be done with the car on the ground and not moving. You will get changes in DF for sensor channels 3 and 4. Channel 3 for 1st, and Channel 4 for 2nd and R. You should see around 22% or 78% DF with a gear selected.
I'd also be checking at the TCU the 5V and 8.5V supplies. If these aren't close to what they should be, disconnect the rear plug on the transmission (the one for the distance sensor and speed sensor) and then check again. You will get a bunch of codes but you can clear these once the plug is back on. This can be done with the engine off.
I'm assuming you have wiring diagrams and know the method to check all of these. If not ask and I'll post some stuff to help.
This is all great advice. One caution though, through my own experience I've found that a lot of multi-meters that claim to measure duty cycle doesn't or give a faulty reading. You can measure dc voltage too and calculate the percentage of the supply voltage. That's your duty cycle. Given the impact on multiple sensors I'd be suspecting the supply voltage. If that is normal, the TCU would be next on my list.
I'm reasonably new to the P-community and was astonished by how much insights and helpful info / advice is available here!
I recently bought a 981 GTS PDK and in the past 2 weeks, I started to notice that:
1. when the car starts cold, Clutch-1 bites really hard - once I let go the brake, the car launches pretty hard even I'm not stepping on the gas pedal
2. however, when the car is warmed up, the opposite happens - Clutch-1 is vague, and I often have to step hard on the gas pedal to get it launched / reversed
Yesterday on my way home, an error "Gearbox Fault, No R Gear" appeared and the car went into limp mode with only Clutch-2 (i.e. gear 2,4,6) left for use. I managed to drive it home and after a couple of hours of cool-down, the car restarted without warning sign. I could still drive it but with the "cold / warm" behaviour mentioned above.
I live in Asia where there are much fewer workshops that specialise in P-cars. Would you very kindly shed some lights on what likely has gone wrong, or point me to the right investigation / repair direction so I can work with local workshops here please?
Would really appreciate you very kind help!! Thanks so much.
I live in Asia where there are much fewer workshops that specialise in P-cars.
To diagnose correctly, you will need someone with a PIWIS, or minimum Foxwell (or similar) to interrogate for actual system codes.
There are some decent third party repair shops on the island, and if you want to venture over to the dark side, Gemballa in Kwun Tong road can likely help with at least the diagnosis...
You can too perhaps, if you're confident with OBD readers?
I'm reasonably new to the P-community and was astonished by how much insights and helpful info / advice is available here!
I recently bought a 981 GTS PDK and in the past 2 weeks, I started to notice that:
1. when the car starts cold, Clutch-1 bites really hard - once I let go the brake, the car launches pretty hard even I'm not stepping on the gas pedal
2. however, when the car is warmed up, the opposite happens - Clutch-1 is vague, and I often have to step hard on the gas pedal to get it launched / reversed
Yesterday on my way home, an error "Gearbox Fault, No R Gear" appeared and the car went into limp mode with only Clutch-2 (i.e. gear 2,4,6) left for use. I managed to drive it home and after a couple of hours of cool-down, the car restarted without warning sign. I could still drive it but with the "cold / warm" behaviour mentioned above.
I live in Asia where there are much fewer workshops that specialise in P-cars. Would you very kindly shed some lights on what likely has gone wrong, or point me to the right investigation / repair direction so I can work with local workshops here please?
Would really appreciate you very kind help!! Thanks so much.
At least read the code with an OBD reader see what it is. But it does sound like distance sensor problem - if the code reads p1731/2/3/4 then it would confirm that.
Whilst you mention you measured the freq output from the sensor, did you measure the duty factor, as this is what the TCU is using for the distance? It does seem very strange that the distances are all offset like you say. It's an easy conversion algorithm for the diagnostic tool, as 50% DF will equal zero distance.
Here's what I would do.
Measure the sensor outputs at the TCU while it's in gear. First I'd measure with the engine off, as 1st will be selected on channel 3, and all the others shouldn't be engaged. Then I'd start the car and measure in neutral (all should have a DF of close to 50%), and also in D and R. D will select 1st and 2nd, and R will only select R. This can all be done with the car on the ground and not moving. You will get changes in DF for sensor channels 3 and 4. Channel 3 for 1st, and Channel 4 for 2nd and R. You should see around 22% or 78% DF with a gear selected.
I'd also be checking at the TCU the 5V and 8.5V supplies. If these aren't close to what they should be, disconnect the rear plug on the transmission (the one for the distance sensor and speed sensor) and then check again. You will get a bunch of codes but you can clear these once the plug is back on. This can be done with the engine off.
I'm assuming you have wiring diagrams and know the method to check all of these. If not ask and I'll post some stuff to help.
That's indeed what I'm planning on doing. Now I know that the cabling is not a likely suspect, the position sensor and transmission ECU are next on the list. Measuring the actual PWM duty cycle and the power supply voltages is what I will probably do next weekend. Since I don't need a car lift for now, I can also do those investigations right here at home.
I have indeed found your other threads on this and other forums to enable me to executes these measurements quite easily. It goes without saying it is amazing what amount of knowledge and insights is present in this and other threads. A huge thanks for that already!
Originally Posted by stjoh
This is all great advice. One caution though, through my own experience I've found that a lot of multi-meters that claim to measure duty cycle doesn't or give a faulty reading. You can measure dc voltage too and calculate the percentage of the supply voltage. That's your duty cycle. Given the impact on multiple sensors I'd be suspecting the supply voltage. If that is normal, the TCU would be next on my list.
I've got access to some nice oscilloscopes, so I don't have to rely on a multimeter reading. You're probably right about a DC voltage measurement permitting to determine the duty cycle, though.
I've got the car which loses clutch #1 (after 15-20mins drive) inspected. Error codes P1781, P0841 and P181A were found. Clutch #1 oil pressure recorded >80psi (vs clutch #2 @24psi). Pressure regulator #1 has no current passing thru with 0mA. Any insights are greatly appreciated! Thanks!
I've got the car which loses clutch #1 (after 15-20mins drive) inspected. Error codes P1781, P0841 and P181A were found. Clutch #1 oil pressure recorded >80psi (vs clutch #2 @24psi). Pressure regulator #1 has no current passing thru with 0mA. Any insights are greatly appreciated! Thanks!
I had nearly the same issue. Turned out to be a faulty clutch pressure sensor. I documented it all in this thread.
I am having intermittent PDK problems and looking for guidance diagnosing the source of the problem. 2010 Cayman S, 987.2, stock 3.4L, 57,000 miles.
The previous owner tracked the car and replaced the PDK twice. I don’t know what failed with the first and second PDK I just know both trans were replaced and not repaired due to the car not engaging into gear.
I am the third owner. I also track the car. The suspension has been modified. I have the service records from the previous owner as follows.
Mods:
March 2014: Paddle Shift Steering Wheel
Jan. 2015: TPC Racing DSC/Tractive electronic coil overs with DDA Valves and Swift 400/500 Springs
DSC Controller
DSC Wiring Harness
Tractive front & rear camber plates
TPC Pro Race sway bars & race links
TPC Pro Race adjustable rear toe links
Guard LSD
Tires: Slicks
Service records:
Oct. 2016, 45,914 miles, repair power steering, PS leaks at pump & lines, replaced pump & pressure lines, repaired coolant leak, replaced heater control valve
Sept. 2017, 47,208 miles, replaced PDK
Performed PDK & DME software updates
Calibrated PDK & verified no more faults
Performed PDK differential service
March 2019, 47,820 miles
Reverse not engaging
Cleared fault & reverse functioned
Recommended & replaced PDK ECM
Recommended dealer install latest software
April 2019, 48,155 miles
Dealer programmed PDK CU, tried calibrating but failed due to faults
All wiring & signals OK
Forward gears working, reverse intermittent
Advised to replace PDK
Aug. 2019, 48,167 miles
Replaced PDK (under warranty)
Oct. 2023, 56,311 miles
Power steering fluid leak. Replaced high pressure power steering line
Installed Bilt Racing Service (LN Engineering) Power Steering Cooler Kit, PDK Cooler Side Mount Kit & PDK/Gear Oil Cooler Kit
Nov. 2023, 56,684 miles
Car would not engage into gear. Put trans in Drive. Dashboard gear indicator flashes “1,2,1,2,1,2”. No forward, no reverse.
Dashboard gear indicator is dark except for when in Drive. N, R, P indicator is dark.
Dashboard Message: “Transmission emergency run”
Turned off car. Restarted car. Car engages into gear.
Reputable Porsche indy shop reads fault codes.
P0700 Transmission fault (signal plausible)
P1691 Communication trans control (no signal)
U0101 CAN timeout engine (no fault systems available)
Removed & replaced ignition coils & spark plugs for testing purposes (no charge)
Found trans fluid flow low
Performed PDK Service & PDK Differential Service
Programmed/calibrated PDK & DME as needed
Installed LN Engineering PDK sump pan (customer request)
Did extensive road test
Found P081A still present
PDK Control Unit would not hold factory values
Recommended & replaced PDK CU
Programmed & calibrated PDK CU. No fault codes. No dashboard messages.
Performed extensive road test
Stopped car, started car. Dashboard message reads: “ Transmission emergency run”
Dashboard gear indicator flashes “1,2,1,2,1,2”. No forward, no reverse.
Dashboard gear indicator is dark except for when in Drive. N, R, P indicator is dark.
Scan for faults: Inactive. Not present. Stored.
DME (DFI) 987S 3.4L:
P1691 Communication trans control unit (no signal)
P169A Communication trans control unit (below limit value)
P1628 CAN interface, sgs no communication (no signal)
PDK:
U0100 CAN timeout engine (no signal)
PSM:
4444 Steering-angle sensor not initialized (no fault system available)
5400 Sport mode fault (no system available)
PAS:
8002 Terminal 15 (exceeds limit value)
C151 Communication Tiptronic control unit (drive)(exceeds limit value)
Instrument cluster:
C151 Control unit communication, automatic trans (drive) (no signal)
Gateway:
C151 Communication Tiptronic control unit (drive)(no signal)
Rear:
C151 Communication Tiptronic control unit (drive)(no signal)
Driver’s door:
C151 Communication Tiptronic control unit (drive)(no signal)
Passenger’s door:
C151 Communication Tiptronic control unit (drive)(no signal)
I understand controlling heat is critical and tracking with slicks and a LSD can generate more heat which is why I recently installed the Power Steering cooler, PDK Cooler and PDK/Gear Oil Cooler.
The two power steering related failures occurred prior to installing the PS cooler and were likely heat related. Hopefully with the new PS cooler it won’t occur again.
The PDK issue is intermittent. There are currently no fault codes pointing us toward replacing the valve body, valve body solenoids, distance/position sensor, temp sensor.
I assume the issue is not heat related because the message “Transmission emergency run”, the flashing “1,2,1,2,1,2”, the dark gear indicator and not engaging into gear occurred prior to installing the PDK cooler & PDK/Gear Oil cooler as well as after installing the coolers. There does not appear to be a wiring fault.
The same error message along with the previously stated symptoms that first occurred in early Nov. 2023 cleared after doing the PDK Service, PDK/Gear Oil Service and replacing & reprogramming the PDK CU but then returned after driving about 100 miles.
I am not sure which direction to go at this point. I am reaching out to the community for guidance. Thank you! Much appreciated!
I assume the issue is not heat related because the message “Transmission emergency run”, the flashing “1,2,1,2,1,2”, the dark gear indicator and not engaging into gear occurred prior to installing the PDK cooler & PDK/Gear Oil cooler as well as after installing the coolers. There does not appear to be a wiring fault.
The same error message along with the previously stated symptoms that first occurred in early Nov. 2023 cleared after doing the PDK Service, PDK/Gear Oil Service and replacing & reprogramming the PDK CU but then returned after driving about 100 miles.
This sounds like typical distance sensor failure, I had similar symptoms when my went out - trans emergency run, the flashing gear display, can't reverse, or missing some forward gears etc. And at the beginning it would work again if I give it a re-calibration but error would eventually return. What is strange though is none of the code you had was directly pointing to distance sensor (P1731/2/3/4)... Did you read the codes when the error was active?
I just talked to the tech working on my car. We are both trying to think outside the box because, as byroncheung and t-design said, the codes are not pointing to a faulty Distance sensor or the PDK CU which was just replaced. Today the tech was looking into the Terminal 15 faults that appeared with yesterday's scan. Terminal 15 is one of the main power sources switched by the ignition key. He measured the values on the Front CU. It was getting 14.9 volts which is too much load on the Front CU circuit and may be due to the alternator overcharging. We will look into the alternator output. The Front CU controls terminal 15 which goes to the instrument panel among other things. Perhaps that is the reason why the dash gear indicator went black. More digging is necessary.
It looks like we found the source of the PDK dash error messages and the Terminal 15 fault codes. They were two were separate issues. When I had "Shop A" install a LN Engineering power steering cooler, PDK cooler and PDK/Gear oil cooler the tech failed to secure the shifter cable to the shifter cable clip in the engine bay when re-assembling the car. As a result the shifter cable was loose. When I tried to shift from Park to Drive the trans shifter lever would not fully engage in gear, the dash gear indicator would flash "1,2,1,2,1,2", the other gears (N, R, P) went dark and the message "Transmission emergency run" appeared on the dash. The "Shop B" tech found the issue and installed the $3.83 clip and secured the cable. No more PDK issues. The Terminal 15 fault codes coming from the Front Control Unit were a result of the wrong spec'd battery having been installed under previous ownership. We replaced it with the proper spec'd battery and there were no more Terminal 15 faults.
Very interesting. Glad you found the culprits and how everything has put back in place properly and spec’d appropriately when any service is performed.
It looks like we found the source of the PDK dash error messages and the Terminal 15 fault codes. They were two were separate issues. When I had "Shop A" install a LN Engineering power steering cooler, PDK cooler and PDK/Gear oil cooler the tech failed to secure the shifter cable to the shifter cable clip in the engine bay when re-assembling the car. As a result the shifter cable was loose. When I tried to shift from Park to Drive the trans shifter lever would not fully engage in gear, the dash gear indicator would flash "1,2,1,2,1,2", the other gears (N, R, P) went dark and the message "Transmission emergency run" appeared on the dash. The "Shop B" tech found the issue and installed the $3.83 clip and secured the cable. No more PDK issues. The Terminal 15 fault codes coming from the Front Control Unit were a result of the wrong spec'd battery having been installed under previous ownership. We replaced it with the proper spec'd battery and there were no more Terminal 15 faults.
What battery is the wrong spec that would cause this fault? Just curious.
11-06-2023, 08:26 AM
