Seeking wisdom, 996T limp mode with fault codes

[shantybeater]

I'm hoping someone out there can help. Car had a major service carried out at the local OPC, I then changed the spark plugs, clutch accumulator, clutch bleed, gearbox oil, brake fluid & fuel filter. All was well for a day or two (with a 3 hour drive in the middle). Car appeared to go into limp mode, no engine lights or obvious running symptoms just 0.1 bar of boost pressure. I disconnected the battery for 15mins and all was well for another couple of days. I ordered a PIWIS cable and the following errors have come up:

P2135
Accelerator pedal
Signal implausible

P0121
Factory Fault Code 117 - Throttle value or accelerator pedal potentiometer
Signal implausible

Has anyone seen these codes before? any suggestions on where to start? Have I likely disturbed something on my travels?

Edited by shantybeater on Monday 14th January 20:37

[Magic919]

My wife suggests starting with the accelerator pedal.

I'll add - Look at the procedure for calibrating it after the battery has been disconnected.

[shantybeater]

Hi Magic, I was hoping this was a common issue but google search shows otherwise. Will try the battery d/c recalibration and go from there. The car battery did run flat at one point so fingers crossed that solves the issue.

Edited by shantybeater on Monday 14th January 20:38

[Vixpy1]

TPS sensor on the Pedal

[Rockster]

shantybeater said:

I'm hoping someone out there can help. Car had a major service carried out at the local OPC, I then changed the spark plugs, clutch accumulator, clutch bleed, gearbox oil, brake fluid & fuel filter. All was well for a day or two (with a 3 hour drive in the middle). Car appeared to go into limp mode, no engine lights or obvious running symptoms just 0.1 bar of boost pressure. I disconnected the battery for 15mins and all was well for another couple of days. I ordered a PIWIS cable and the following errors have come up:

P2135
Accelerator pedal
Signal implausible

P0121
Factory Fault Code 117 - Throttle value or accelerator pedal potentiometer
Signal implausible

Has anyone seen these codes before? any suggestions on where to start? Have I likely disturbed something on my travels?

Edited by shantybeater on Monday 14th January 20:37

You did all that after a major service at the OPC? What did the heck major service at the OPC involve?

Anyhow the codes (obviously) point to a problem with the e-Gas pedal so that's where I'd look. Maybe.

Hard to imagine you upsetting that during your servicing of the car.

That the car ran ok afterwards suggests the e-Gas problem is a coincidence or a red herring... More below.

Not much to look at really. You can try disconnecting the battery then re-calibrating the e-Gas.

After connecting the battery turn the ignition key to on and leave it in the on position for 60 seconds. Do not press the gas pedal. Turn the key to the off position. Wait 10 seconds. Then turn the key to on and then to start and start the engine. Done.

My WAG is in changing the plugs -- though you were in the engine compartment big time and you could upset something else too -- you introduced an intake leak. After you do the e-Gas recalibrate thing and it doesn't help look at the last thing you touched.

[Porkupine]

Magic919 said:

My wife suggests starting with the accelerator pedal.

I'll add - Look at the procedure for calibrating it after the battery has been disconnected.

Is your wife a mechanic magic?

[Magic919]

She's an accountant.

[shantybeater]

Thanks for all the replies.

As per Vixpy's response, is there a way of checking actual values through the sensor via Durametric?

Rockster - I know it sounds silly but I want to keep the service book in check for resale, anything over and above I will be doing myself where I can. OPC carried out the normal major service e.g. oil/oil filter/pollen filter/air filter and the usual inspection checks. Anyway thanks for the suggestion, I will try the recalibration. I was thinking the same (but hoping it wouldnt be!) regarding a boost leak, the plug change did involve removing the intercooler hoses on both sides.

Edited by shantybeater on Monday 14th January 21:31

[Rockster]

shantybeater said:

Thanks for all the replies.

As per Vixpy's response, is there a way of checking actual values through the sensor via Durametric?

Rockster - I know it sounds silly but I want to keep the service book in check for resale, anything over and above I will be doing myself where I can. OPC carried out the normal major service e.g. oil/oil filter/pollen filter/air filter and the usual inspection checks. Anyway thanks for the suggestion, I will try the recalibration. I was thinking the same (but hoping it wouldnt be!) regarding a boost leak, the plug change did involve removing the intercooler hoses on both sides.

Edited by shantybeater on Monday 14th January 21:31

All I can tell you is what the techs tell me. That installing the hoses after removing the intercoolers is a pain in the neck in that the edge of the hose can have a loose piece of rubber, a flap of rubber, that gets bent back as the hose is slid over the hose connecter.

While the hose appears to seal tight and may tolerate a test drive it will leak over time. The techs take particular care in lubing the hose diameter that fits onto any hose connection and checking for any loose areas, any flaps of rubber and making sure these go on first to avoid bending back the loose area, the flap, and thus creating a leak.

Of course if the hose is too bad it needs to be replaced. But with care and proper handling they can last a long time. My Turbo has had 3 plug changes now and the original hoses are still in service and still sealing just fine.

[gtphile]

With those fault codes, it appears the throttle potentiometer above the throttle pedal has gone faulty.

If you look under your dash, you will see a cable running from the pedal, up to the potentiometer. That reads throttle inputs.

There are actually two potentiometers in it, one that starts at high voltage, and drops when throttle opened, and vice versa.

You can read those figures on durametrics AFAIK. You certainly can with the Porsche software.

That would be a start point for you.

Rockster, you are quite right though, the intercooler hoses cause a few problems! there is a later o-ring which is much better.

[shantybeater]

gtphile said:

With those fault codes, it appears the throttle potentiometer above the throttle pedal has gone faulty.

If you look under your dash, you will see a cable running from the pedal, up to the potentiometer. That reads throttle inputs.

There are actually two potentiometers in it, one that starts at high voltage, and drops when throttle opened, and vice versa.

You can read those figures on durametrics AFAIK. You certainly can with the Porsche software.

That would be a start point for you.

Rockster, you are quite right though, the intercooler hoses cause a few problems! there is a later o-ring which is much better.

Thanks for the replies. I've had a nosey in the dark but will take a better look this weekend. I disconnected the battey for 15 mins and noticed the codes reappeared once ignition is at 1pm. I cleared the faults several times and it appears the car is aware of the fault before startup - this rules out a boost leak I would think?

Readings at idle:
Throttle position sensor 1 - 0.74v
Throttle position sensor 2 - 4.27v

[Rockster]

shantybeater said:

Thanks for the replies. I've had a nosey in the dark but will take a better look this weekend. I disconnected the battey for 15 mins and noticed the codes reappeared once ignition is at 1pm. I cleared the faults several times and it appears the car is aware of the fault before startup - this rules out a boost leak I would think?

Readings at idle:
Throttle position sensor 1 - 0.74v
Throttle position sensor 2 - 4.27v

After you reconnected the battery did you do an e-Gas calibration? I don't think it matters in this case but you should do it just in case it does.

Barring something related to not doing the calibration that the error codes come right back at engine start is because the fault is present at engine start.

I agree: this rules out (almost certainly) a boost/intake air leak. But at least you now have or should have more confidence you are on the right track.

Not sure what the voltages should be. Maybe you need take this reading from another car with a known good e-Gas?

[shantybeater]

I appreciate the help on this rockstar. I carried out an egas recalibration straight after battery reconnection. As soon as the car was switched to ignition 2 the codes appeared. I turned backed to pos1, cleared codes and tried a second egas recalibration. Codes were present again

[davek_964]

If nobody posts before, I could check what my car shows when I get home this evening.

[shantybeater]

Davey that's very kind of you to offer but someone has already done this over on 911uk. For reference:

http://911uk.com/viewtopic.php?t=79954

Will post up results tonight, thanks for the help!

[shantybeater]

Just to wrap this thread up (for future searches out there) the culprit was the throttle poteniometer:



Worth mentioning this part is shared with the 986 Boxter range.

Thanks for all the help!

[mez3]

Nice one.

It's been bookmarked for ( possible ) future reference.

Cheers