Th Dude

Hi all,
Just received my 03 tt today.

It came with the CEL illuminated. I cleared a misfire code, drove about 20 miles, and took the car to get a California smog inspection.

The car passed all of the emissions and visual checks. However...

"This vehicle failed the MIL/Check Engine Light due to failure to successfully complete all OBD self tests."

The smog tech suggested that the battery may have recently gone dead and caused the computer to require a reboot. He suggested that I drive the car 50 miles or so to allow the system to recalibrate.
I drove about 80 miles. This did not resolve the issue.

Any thoughts?

Thanks in advance,
D

UPDATE: Complete this drive cycle to solve this issue

neanicu

It is very important to find out everything about that misfire code. Just clearing the code won't solve the issue. It will come back most likely. It could be spark plugs,coils etc.
Which code was it?

Th Dude

Thanks for your reply.

The code is P0303

Previous owner claims to have recently changed plugs, cleaned MAF, new 997tt coil packs, new air filter.

"02996ttx50

may not impact your emissions test, though it probably has: "cleaned maf".

replace the maf. 80 bucks on ebay.

neanicu

This is what it means:
P0303

510 Misfire, cylinder 3
Diagnosis conditions
• A cycle of 1,000 crankshaft revolutions is evaluated (for misfire
damaging to the TWC, 200 crankshaft revolutions). The misfire
rates are compared with a threshold value. If the misfire rate is
greater than the threshold value, a fault is recorded in the memory.
• The Check Engine Malfunction Indicator Lamp (MIL) is switched
on and stays on when the misfire rate lies above the threshold
value at which the emission limit values are exceeded during two
consecutive driving cycles (in the case of EOBD 3 driving
cycles).
• If the misfire rate may lead to permanent damage to the TWC,
the Check Engine MIL flashes. If the misfire rate is no longer
reached during the first journey, the MIL goes out. If the rate is
reached during the next journey, the MIL flashes. If this misfire
rate is subsequently no longer reached, the MIL changes to a
continuous light.
♦ When using a block heater (for heating coolant), start and driving
off difficulties or misfiring can occur if the block heater was connected
for less than 4 hours.
♦ When the fuel tank is driven to empty, misfiring can occur. For
this reason the fuel level in the tank is also stored in the memory
when misfiring occurs. If the tank was nearly empty, there was
probably no fault. Erase fault memory and road test vehicle.
♦ In the event of a short circuit to B+ or ground in the oxygen sensors
ahead of the TWC, the mixture becomes too lean or too
rich. This can cause misfiring. If, in addition, an oxygen sensor
signal fault ahead of the TWC is stored in memory, first correct
this fault and then road test the vehicle.
Possible fault cause
♦ Fault in ignition system
♦ Fault in injection system
♦ Flat-base tappets (valve lift fault)
♦ Mixture too rich
♦ Mixture too lean

neanicu

There could be a few reasons this misfire occurred. So before you start doing all the recommended tests,is this the only code that came up?

Th Dude

TY.
While the CEL was on, it was not blinking.

Interestingly, the "misfire" self diagnosis shows as "complete" and no further codes have been logged...as of yet.

Here is the status of the various "readiness indicators":

Misfire - complete
Fuel system - complete
Comprehensive component - complete
Catalyst - not complete
Evaporative system - not complete
Secondary air system - not complete
Oxygen sensor - complete
Oxygen sensor heater - complete

Th Dude

Yes

neanicu

I don't see the mechanical causes(Variocam,valve lifters etc) described here to be the issue in your case,so moving on :

Diagnosis/Troubleshooting
If there is a lot of oil in the engine, check that the oil filler tube and
cap are tight.
Note!
Note!
Work instruction Display OK If not OK
1 Check for air leaks in intake air system ⇒ Step 2. Repair intake air
system
→ End.
2 Carry out pressure loss test ⇒ Step 3. Repair engine
→ End
3 Check spark plugs.
Specified spark plugs:
Electrode gap: 1.6 mm ± 0.2 mm.
Check appearance of spark plugs
⇒ Step 4. Replace faulty spark
plug(s).
→ End
4 Check spark plug connectors Approx. 2 kΩ
⇒ Step 5
Replace faulty spark
plug connectors.
→ End5 Check ignition coil(s) ♦ Measure resistance between Pin
1 and Pin 15
0,3 to 0,7 Ω
(at 20 °C)
⇒ Step 6.
Replace ignition
coil(s)
→ End
6 Check all connectors for secure fastening and corrosion ⇒ Step 7. Clean plug connections
and connect
securely.
→ End
7 Check fuel pressure ♦ Undo and remove the closure
cap of the fuel collection pipe
test connection (A/F 13 mm)
♦ Connect pressure gauge (special
tool P 378a) to connecting
line (special tool 9559) and connect
to test connection.
♦ Actuate fuel pump, either with
the Porsche System Tester or
via a fuel pump relay without
tester
⇒ Step 8.
♦ Nominal test value, stationary
engine
3,8 ± 0.2 bar
♦ Nominal test value, engine idling 3,3 ± 0.2 bar
⇒ Step 9


There're a few more references here,but I don't think they're relevant.
I'm still thinking of a spark plug or a bad coil.
I would try to drive a bit and the monitors might settle eventually.
There's a test to be performed to settle the monitors,I'll check to see if I can find it...

RangerDick

Ran into the same thing with one of my cars. Swapped out my evil, smog producing piggyback chip and cleared any stored codes initially did not pass the OBD self check. When you cleared the CEL and stored codes, it puts the OBDII into an evaluation mode which will not allow for the system to pass smog until a certain number of restarts/miles is put in. Did you tell the tech you cleared your CEL code yourself? I bet he is assuming the battery was disconnected, which has the same effect as clearing your codes.

neanicu

Here's a link to a very good post :

https://rennlist.com/forums/997-foru...nspection.html

There's a test to be performed described in this thread to settle the monitors.
Good luck!

Th Dude

I'm hoping this is the case.
No, I chose not to disclose that I had recently cleared the CEL.

Link not working.

neanicu

Try now!

Th Dude

32krazy!

you need to do a drive cycle. its a common thing. is your car flashed with a tune? its possible the tuner has turned off the rear cats. its something thats done frequently. if it is you need to contact them as you will never pass with the rear O2 sensors off. thats prolly what the catalyst not ready is reading