chamilka

I have a 2004 Porsche Cayenne S with over 114,000 miles.
I am getting “PSM Failure - Workshop" message very frequently now. Once the error has been there for few days, the Cayenne would start to move so slowly to a point it is not drivable. When the errors are cleared using Durametric, all problems would disappear and the Porsche will be alive and well for few weeks until the same error comes back. I noticed that the PSM workshop error would appear mostly when cornering, or with sudden acceleration.
The main battery looks pretty good (I think it is the original) and reads 11.8 when tested using a volt meter. I did not test the secondary battery under the rear cover since it is only for start up. the Tire pressure is good.
Per my Rennlist research there is a chance that DME control module replacement may be the answer, but I would like to get your opinion before jumping the gun. Please look at the errors listed below and let me know the order in which I should tackle them and how. As always I appreciate your advice and support.

Following are the set of errors I get regularly when tested through the diagnostics interface each time with “PSM Failure - Workshop" error:

Bosch Digital Motor Electronics 7.1.1
P0011: A Camshaft Position -Timing Over- Advanced or System Performance B1 –
P2186: Throttle/Pedal Pos. Sensor/ Switch ..Voltage Correlation
P2174: Throttle/Pedal Position Sensor/ Switch E Circuit –
907: Load management operat. on vehicle electrical sys./DME control module
1520: Rain sensor/light sensor - Implausible signal
2197 Potentiometer for footwell lights

Porsche Stability Management (PSM/ABS8)
1314: DME control module, Please read out fault memory

Air Conditioning
709: Sun sensor, Open circuit/short circuit to ground
1336: CAN comfort OFF, No signal/communication


Thank you kindly
Chamilka

User 4221

This is going to sound like a broken record but the PSM-Workshop failure (repeatedly) is usually a failing battery.

Pull the batt and have it load tested.

hahnmgh63

Exactly, start with a new battery at the least as a fully charged 12V. battery should be close to 12.8V. If it reads 11.8V after sitting a short while it is shot. Get a new battery, clear the codes and give it a try again.

chamilka

Ok thanks, let me get a new battery and see if that resolves the problem. Just the main battery right?

User 4221

Correct..... Main battery under the driver's seat.

XR4Tim

The load management fault is a sign of a failing battery or charging system.
If you still have problems after replacing the battery, look into the P2174 and P2186 faults. They will cause your PSM light and driveability issues, and will be caused by a faulty gas pedal, throttle body, or wiring.

Slow Guy

+955

And still on the original battery you've gotten your moneys worth out of it. IMHO anything over 5 yrs. on a car battery is gravy.

chamilka

Ok installed a brand new battery, Cleared the codes, took for a test drive (2 miles), stopped the car for about 1 min, started back drove for about one minute and : the PSM error message came up followed by drivability issue (no throttle).
Diagnostics errors we as follows:
In addition to PSM error, I got 2197: Potentiometer for footwell lights and also a faulty sterring sensor error.
I cleared the errors again and drove back home, checked for any errors – none
But I am sure the issue will reappear again tomorrow .
Ok so could you please help me organize my plan of attack to repair?
First of all what is P2197: Potentiometer for footwell lights means? Which part is this?, Do you think this error also relates to P2186 & P2174 errors.
Does anybody have experience replacing whatever is needed for errors: P2186 & P2174?

User 4221

The potentiometer for footlwell lights is the light control panel that resides in the roof console next to the sunroof dial.

It is a fairly common failure item and I think the updated version corrected this issue.

XR4Tim

Right. I've seen very few Cayennes that didn't throw the Potentiometer for Footwell Lights fault.
For the two relevant faults, I would start by looking at the data from both throttle position sensors. They should be the inverse of each other (the voltage of one sensor increases, and the voltage of the other sensor decreases when the gas pedal is moved). You get the voltage correlation fault (P2186) when they don't coincide. You need to determine whether it's the sensor at the throttle body or the sensor at the gas pedal that's not reading properly. The problem could be as simple as a bad connection at the throttle body harness (I had this problem on my X5, and it would randomly throw it into failsafe mode), or it could be a malfunctioning gas pedal or throttle body.

chamilka

Here are the Actual values. I started the car and press the gas pedal several times.

Throttle-valve potentiometer 1 = 15.23%
Throttle-valve potentiometer 2 = 80.85%
Pedal-travel sensor potentiometer 1 = 14.0%
Pedal-travel sensor potentiometer 2 = 7.03%
Potentiometer 1 voltage emergency air = 0.78V
Potentiometer 1 voltage lower stop = 0.52 V
Potentiometer 2 voltage lower stop = 4.4 V
Throttle-valve angle potentiometer 1 = 0%
Throttle-valve angle potentiometer 2 = 0%
Pedal value = 0%
Throttle plate angle load signal = 0%
Throttle angle actual value = 0%
Throttle angle nominal value (adaptation) = 0%

So what do these values mean?

XR4Tim

You'll need readings from several different pedal positions. Focus on Throttle-valve potentiometer 1 and 2, Potentiometer 1 and 2 voltage, Pedal value, and Throttle angle actual value.
See if any of them work with the key on and engine off, so you can get a full sweep up to WOT. You're going to want to see if Pedal value, or one of the Potentiometer voltages is not moving correctly when you press the gas pedal. This will confirm or rule out a faulty gas pedal.
Since it seems to be an intermittent problem, this might take some time.

chamilka

Following are several different values, after cleaning TB and two MAF sensors.

1) With Key on, Engine off, & Gas pedal not pressed:

Throttle-valve potentiometer 1 = 16.01
Throttle-valve potentiometer 2 = 83.59
Potentiometer 1 = 0.59
Potentiometer 2 = 4.56
Pedal value =0
Throttle angle actual value = 0

2) With Key on, Engine off, & Gas pedal pressed 100%:

Throttle-valve potentiometer 1 = 83
Throttle-valve potentiometer 2 = 16
Potentiometer 1 = 0.540V
Potentiometer 2 = 4.56V
Pedal value = 100%
Throttle angle actual value = 100%

3) With Key on, Engine off, & (pedal pressed 1/2 a way):
Throttle-valve potentiometer 1 = 57.42
Throttle-valve potentiometer 2 = 42.18
Potentiometer 1 = 0.540V
Potentiometer 2 = 4.56V
Pedal value = 0% (***** is this a problem?)
Throttle angle actual value = 0% (***** is this a problem?)

4) While engine running (while idling):

Throttle-valve potentiometer 1 = 12.5
Throttle-valve potentiometer 2 = 87.1
Potentiometer 1 = 0.540V
Potentiometer 2 = 4.56V
Pedal value = 0%
Throttle angle actual value = 0%


5)While engine running (while pressing the gas pedal):

Throttle-valve potentiometer 1 = 17.5
Throttle-valve potentiometer 2 = 82.1
Potentiometer 1 = 0.540V
Potentiometer 2 = 4.56V
Pedal value = 0%
Throttle angle actual value = 0%

XR4Tim

Okay, the pedal value and throttle angle actual value at 0% does seem weird to me, but the throttle valve potentiometer values are correct. If you've got two Cayennes, like your signature shows, I would scan the other one, and see if you get similar values or not.

chamilka

Tim – excellent idea!! I don’t know why I didn’t think of comparing values with my other Cayenne given they are identical models. I will do it now and let you know the results.
BTW- Tim got your PM (phone number etc) , Thank you so kindly for all your help.