yelcab

I have a diagnostic question regarding this issue. The basic problem is both the key fobs are not being detected by the car and do not open the car or start the car 90% of the times. According to the post below, the solution is the dealer using some kind of tool to measure the signal strength from the key as seen by the car. The signal was way lower (40-70) than expected (140-190). The solution was replacement of the Amplifier (booster) board, and a coax cable.

2018 Panamera key doesn't work?? - Page 2 - Rennlist - Porsche Discussion Forums

I do not have whatever Porsche tool that is. I only have a X431 Mini Pros tool that does offer some data on Front End Electronics which include some antenna Field Strength.

So my questions are: 1) what kind of tool is being used at the dealer to measure the variable above? 2) what are those units, mA, mV, ? 3) Is it measured while pushing the key fob with engine off, key out?

huskeric

The keyless entry antenna (see below pic) is located in the rear hatch under the carpeted cover. You may want to try removing this carpeted cover/flooring and then trying the remotes. You will have to remove the stainless floor mounting tabs.

A few months ago, I added some dynamat under this cover and inadvertently covered the antenna, rendering the keys inoperable... Took me another day to realize I covered this antenna with dynamat. Initially, I changed the fob battery, tried the other fob, etc... nothing worked. Then, I realized the dynamat covered the antenna - DOH!
Let me know if you need some pics of the location.

sac02

This is a little out of my wheelhouse, but I'll throw out the $0.02 I know. This is for investigating the key fob (transmitter), not the receiver in the car

• Radio transmit output power is measured in Watts, or if you are acting as a receiver, you measure Watts per square meter. (or some variation of that unit, say mW/mm^2) But with a reference signal it can also be scaled to dB.
• If the issue is the key fob, not another piece in the system, you could have issues for two reasons:
  • Signal strength is weak. Could be battery (I assume you put in new coin cell, but try another, from a different brand / package), could be something else.
  • The fob is not (or is intermittently) transmitting on the wrong frequency (say the transmitter module is going bad and cannot reliably maintain a 433MHz modulation, maybe the communication works if the signal varies a few MHz, but not on the days when the chip sends at 415Mhz (I have no clue what the error tolerance of the system is for this, I just know it's a way that RF devices are able to fail)).
• Vehicle remote fobs work on RF, at a predefined frequency, like 315MHz, 433MHz, etc. I don't know what frequency Porsche uses.
• You can buy a tester on amazon for $20 that will tell you which frequency your key uses (but if someone on this board can tell us, you can skip this step).
• The device you'd be looking for have keywords along the lines of field strength tester, RF detector, EMF meter, spectrum analyzer, etc
• A quick Amazon search for the above keywords give cheap ($50) results that just light up a couple LEDs for generic "signal strength", and more expensive devices that appear to give variable data.
  • I would not be interested in the cheaper ones, how do you know what in the world "three bars" means? Give me actual numbers.
• I do not know what the signal strength of a "good" key fob should be, so I'd advise you to test signal strength against a known good key if you were to get one of those doo-dads to play with.

lexhair

FWIW, my 2014 was having significant issues with periodic and seemingly random key fob failures. There was always a 'forgetting of seat settings' associated with it or even the hatch not opening. I thought it was the body control module but before I jumped on that, I switched to the backup key. Haven't experienced issues with the severity or frequency of this behavior. It makes no sense to me that the primary key fob was causing this behavior so I can't explain the backup key approach.

yelcab

I am writing off the key fobs fault. Both fobs do not work, even with new batteries.

yelcab

So I hooked up my Launh X431 Pros Mini scanner and read the Front End Electronics real time data with car on, not running. There are six antennas on the car and the Field Strength of the six Antennas are:

A1 through A6
1D45
1D1D
1BD8
3326
27A3
1D20

It is obvious that these numbers are in Hexa Decimal format and four of them (1, 2, 3, and 6) are much smaller than the two (4 and 5).

The problem for me is I do not know what values I should be seeing with these. So not much can be read into the data.

Does anybody know?

sac02

Values in the 70 would be in the realm of possibilities (scale the values by 0.01). Those other two values, not so much.

Do the live data values change when you press the key fob buttons?

If so which ones? All of them?

Could you have a helper press the key fob while standing to the left/right/front/back of the vehicle while you monitor live data inside, to potentially determine which data stream is which antenna?

yelcab

According to my scanner, the below are the locations of the signals. While sitting in the car, pushing the fob buttons do not change those values. Although, I don't know if the sampling rates of the real data stream is fast enough to catch the milliseconds pulse of the fob being activated.

yelcab

Thank you for the clue "scale by 0.01". The four signals are lower than 90 which indicates they are below acceptable strengths.

Here is the diagnosis on a different Panamera by the Porsche dealer. Note the "bad" value read to be 70-90 and the good value to be "over 140"

Their fix is to replace the "signal booster" (amplifier) and new wiring to rear module. I should go looking for where / what the amplifier board is.

yelcab

So, I replaced one of the amp booster boards on the car and it does not seem to change the field strengths much. There are two other amps and they are not available until end of June. Perhaps they will make a difference.

For future reference, the Amp Booster Units (left and right) are located under the tail gate to the sides left and right. You access them by lifting up the tail gate hatch back, and pull off the forward center plastic cover, and the left and right plastic covers. The boards are visible immediately.

yelcab

I could use some hints as to how to remove the carpet...

yelcab

@sac02, how did you determine the appropriate values to be close to 70 and not close to 140? Is there documentation somewhere?