Does your 997.1 TT have a P0021 Code?
So you're driving along happily in your stock, modified 600hp or 700hp 997.1 Turbo one day, and you get the dreaded chime for a check engine light (CEL). You pull over somewhere safe and bust out your OBDII code reader and get the “dreaded” P0021 trouble code. The car seems to be otherwise fine, so you clear the code and continue on your journey. At some point in the next few hours or days of driving the gut- punching CEL pops up again with that same code, only now you might even see the associated P03xx misfire or P0011 camshaft position codes. Obviously clearing the CEL with your OBDII reader won't solve the problem. At this point you might want to pour yourself a stiff one (or turn on some relaxing music to chill out) and settle in for a bit of a bumpy and likely costly but FIXABLE ride.
The Mezger-based engine evolved over many years/iterations with a rich heritage both in racing and street form and in its final swan song as used in the 997.1 Twin Turbo, GT2 and later GT2RS. We know from our first-hand experience what a great platform it has become for enthusiasts looking to push the envelope with high horsepower modifications. It's common knowledge and widely accepted in the tuning community that the bottom end has been and can be reliably pushed to 700hp from bolt-ons alone. As with any of these remarkable hand-built legendary engines, you're still going to come across a handful of issues, some of which are not cheap/easy to fix or easy even to address. The most-widely talked about and known is the coolant pipe issue (affecting all GT1 engine based cars so don't feel picked on), which also requires an engine out. Then you've also got your hydraulic clutch/accumulator issue, your hydraulic wing actuation and so forth (none of which are too worrisome to address). Owning a 997TT these days might seem like it isn't for the faint-hearted (keep in mind they're not new anymore), but dare we say they are quite valuable and venerable machines. If you haven't already taken out the Mezger engine to address the coolant pipe fix (and Shark Werks’ 3 elbows), you're going to want to address that at the same time as the one we're addressing here. On the plus side, you're effectively killing two birds with one albeit expensive stone, and the car should run for a very long time trouble-fee. We recommend an overhaul, including new hose kits for a 6 speed or a Tiptronic (it's also good time to do the coolant expansion tank, water pump and thermostat and install new spark plugs).
So what's this P0021 Thing Anyway?
A quick search engine look-up shows this tasty morsel:
"The P0021 code indicates that the Engine Control Module (ECM) senses that the position of the intake camshaft on the ‘bank two’ side of the engine is more advanced than what the ECM has set it to be." Great but how about something more specific from Porsche?
Inlet camshaft control
This error is entered if the actual value varies from the target value by between 5° und 14° of the camshaft for a duration of 2 to 5 seconds.
D Battery voltage 10 ... 16V
D Time after engine starts > 30 seconds
D Engine and engine oil temperature -9°C ... 106°C
D Engine speed 1160 ... 6000 rpm
D No solenoid hydraulic valve final stage error
D No camshaft sensor or crankshaft sensor error
Possible fault causes
E Mechanical fault in solenoid hydraulic valve (sticks, sluggish, blocked)
E Dirt in the oil circuit
E Sealing strips on VarioCam adjuster faulty (leaky, sluggish)
E Oil pressure too low
E Mechanical fault in VarioCam adjuster
The VarioCam in the 997 TT by design adjusts the variable intake cam timing via oil pressure and utilizes a press-fit sleeve inside the cam. The design (questionable) is such that it can and in the case of a P0021 code, will spin internally and block/impede the oil passage into the variable cam sprocket itself. Don't worry as it's not going to completely prevent the flow of oil, but it will do so just annoyingly enough to sometimes prevent it from reaching the target angle and hence cause a check engine light (there's your P0021). In a nutshell your camshaft has spun internally (you what?!). Your camshaft deviation/activation/timing adjustment is being inhibited and the ECU is getting incorrect readings back. These cam timing adjustments and valve lift are controlled by the ECU, which is looking for targets once solenoids open and have pressurized oil flow downstream. If the sleeve inside has spun and moved this blocks said passage and 'ding' CEL, which is the response to overshoot or undershoot of the target cam angle. This issue and code, first and foremost, isn't common so 997TT owners can relax a little. Unlike the dreaded coolant-pipe issue which affects or will affect just about every single one of these cars at some point, the P0021 bastard hasn't manifested itself in anywhere near the numbers of cars. We have seen and fixed a handful of these 997 TT's both in 6speed or Tiptronic trim in years ranging from 2007-2008. Could it happen to the 997 GT2 and GT2RS in theory yes? Although we haven't seen any (yet). "But my car is stock!" won't get you a pass here either as it happens on modified AND/OR stock cars. There seems to have a manufacturing run/issue with some portion of camshafts which were bored out too bigf or the sleeve itself was made too small. We don't expect to see the failure rate to be as high as the coolant pipe issue but there isn't a good way of finding out if you're affected until you get the CEL code. Although not initially terminal, we've heard of people continuing to drive and reset the code. We do NOT recommend doing so long-term. Get it fixed or else...
Below is a shot of a problem/spun camshaft with the hole passage blocked (can't see the yellow background):
This is how it SHOULD look instead below:
If you're very lucky...
You can attempt to change the two cam timing sensors, which really cause the P0011 codes. They're around $100 a piece and obviously that's an easy change. They are known to fail and should be changed regardless of the extent of work you're doing. Most likely however this will not fix the actual issue, which is a spun camshaft (sounds scary but wait... there's more!). Once the engine has been removed and camshaft cover set aside (after a few long hours it should be said) you'll need to have the camshaft removed and inspected. From the pictures below you can see the culprit clear as day. A proper functioning camshaft will have a hole which you can see right through. If the sleeve has indeed spun/rotated, you won't be able to see clean through (maybe partially) and neither will the oil as it becomes blocked. Sometimes they're not completely blocked and still have a partial pathway left but even this will be enough to cause the nasty code. To fix this we have gone with a fixture/tool to help us align, set and then pin the sleeve into the correct position. As you can see below the pin is installed and the oil passage is now back to fully-open. Only now can you go ahead and reinstall and re-time the camshaft with factory precision tools. It goes without saying you will need to clean all gasket surfaces thoroughly before re-installing. Avoid any leaks by doing so with new gaskets, seals, and hardware of course. Don't get sloppy at this stage or you'll be having cam cover leaks like an air-cooled car and there's no reason to join that club in this manner.
Out comes the engine and the auxillary parts are stripped away:
Cam Cover removed now and here's your camshaft culprits:
And the Camshaft adjusters which you'll be using wrenches on to time the cams later:
Here is the cam timing sensor on one side (replace them of course):
The fix is underway
In our fixture getting pinned:
Have a Pro tackle this
This type of job will require time, patience and time to get scheduled (we've had cars sent to us from various areas to upgrade, fix this issue and do a coolant fix) so plan ahead with whoever is going to be undertaking the job. Unless you're a trained tech, brilliant at reading directions, and good with lego or a masochist do not attempt this as a DIY at home. As we were saying this is going to sound a little scary, irritating and likely make a sizable dent in your ownership plans/budget because the only way to fix this is for your engine to come out and get taken apart to a degree. Not everyone is well versed in performing this procedure so be sure to check/confirm that whoever is doing the job has done this type of work before. It involves having to use some specialized factory tools for the re-timing of the camshafts. After the fix has been performed, the reassembly can take place. We won't get into the methodology here in terms of weld vs pin for the coolant pipes (we do the later) but just get it done at the same time (can't stress this enough) and go on to hopefully have many trouble-free 997TT miles...
Sharkwerks Pinned Camshaft ready to go back into the engine:
And of course before the engine goes back in the coolant pipes are all pinned
Parts We recommend when doing this job
- new cam timing sensors
- perform a coolant fix (and replace the Sharkwerks coolant pipe elbows)
- new factory hose kit, 6speed or Tiptronic
- replace the coolant expansion tank, water pump, thermostat
- good time for an upgraded stage II clutch or OEM if you prefer
- Upgraded new engine mounts (stock may be tired and worn)
- spark plugs (why not)
- oil obviously
- Stress Relief Tea
For Reference and From the Porsche Manual for a 996TT with DME 7.8
Position of Camshaft in Relation to Crankshaft, Bank 2
– Below Limit
• Idle speed
• Reference mark recognized
• Engine speed between 600 rpm and 1200 rpm.
• Engine temperature greater than 40 °C
• No fault in camshaft position sensors
• Reference mark OK
• No fault in camshaft adjustment
• No fault in engine temperature
• No fault in camshaft adjustment output stage Possible fault cause
♦ Allocation of camshaft to inlet camshaft incorrect Affected terminals
This fault is stored if the engine was disassembled and the allocation of the camshaft to the inlet camshaft was incorrectly set.
Work instruction Display OK If not OK
1 Set camshafts ♦ To adjust the camshafts, please refer to the 911 Turbo (996) or 911 Carrera (996)