Forgive me for the dumb question, a bit new here. My 1998 993 recently put up the check engine light. I purchased an Ancel AD310 OBD II scanner from Amazon for $20 (note - if anyone has issues with OBD device giving errors like "Failed to Connect", you need to play around with locking and unlocking the car since i think something funky is going on with the immobilizer), and it gave me error code "P0410 - Air System A, Generic".

Can anyone point me in the right direction with regards to:
1. On a scale of 1-10, how bad of a problem is this? I assume i can still drive the car but I should get this fixed
2. On a scale of 1-10, how difficult would this be for me to self-diagnose and repair?
3. What steps / tips should I start to do to diagnose and make this error go away?
4. If i can't DIY fix the issue, how expensive of a repair will this be with a local mechanic?

 

That looks like an invalid fault code, I guess your scanner is not compatible with your car. Only a handful of OBD systems will work properly with the OBD-connected control units in the 993.
-Rennlist Scantool with self-made serial adapter or T-OBD
-Porsche toools as KTS 301, (9288) PST-2 and PIWIS v1/v2
-Durametric
-Jenniskens PDT/UDT999

Here is the list of valid fault codes in the Motronic engine control unit:

11=Power supply, DME, high
14=Engine temperature sensor 2
15=Throttle Potentiometer
16=Throttle Potentiometer
18=RPM Signal
19=Speed signal / Speedometer
21=Hot-wire mass air flow sensor
22=Oxygen sensor (Sensor signal)
23=Oxygen regulation / stop (intake air leak?)
24=Oxygen sensor short to+ or 0 Volts
25=Intake air temperature sensor
26=Ignition timing change
27=IAC opening/closing winding
28=IAC opening/closing winding
31=Knock sensor 1
32=Knock sensor 2
33=Control unit faulty, Knock computer
34=Hall signal
36=Idle CO potentiometer
41=Control unit faulty
42=Fuel pump relay (DME relay)
43=Tank ventilation valve
44=Auxiliary air pump relay
45=Warning lamp Check Engine
51=Injection valve 1
52=Injection valve 2
53=Injection valve 3
54=Injection valve 4
55=Injection valve 5
56=Injection valve 6
67=Ignition final stage
68=Ignition final stage
69=Ignition final stage

Cheers,
Tore

 

Read here; https://rennlist.com/forums/993-foru...ode-po410.html

 

Loren, thanks, so this is a SAI problem. Do modern scanners translate fault codes to a generic format, and/or will US Motronic units report other codes than the normal ones?
Cheers,
Tore

 

Yes, most OBDII scanners can connect to '96-'98 993 DME ECMs, and report readiness states, fault codes and actual values. I have one of these in all my vehicles & in my shop too;
https://www.autel.com/mk1/3239.jhtml

 

I'm confused - is my error code valid / do I need a new OBD scanner? I read that thread from 2003 and didn't come away with any great answer (do I need a top end rebuild? Does this error not matter at all and I should just try "clear" / "reset" it?) but maybe I need my morning coffee first...

 

Had the same issue on a 98 C2S that I owned. Fought it for 6+ years chasing different solutions.....the check valve, replacing weak O2 sensors, etc. I still would get an intermittent 0410 and/or 0411 codes stored. I would just clear the codes and wait till they showed up again since it was just intermittent.

The one that finally worked was something that was posted on Rennlist. I tried a search for it to give you some direction but was unable to find it. Here's what I did and it worked very well. I removed the exhaust headers to expose the ports. I took a short piece of bicycle brake cable and attached one end in my drill. I ran the cable through up through the SAI port and some of the ports were clogged. It's like a roto-rooter. I moved the cable in and out and until there was no resistance felt on the cable. On cyl 3 and 6, the cable doesn't go in as far as on the other cylinders but it does clean them. Once I did that, never had a 0410 or 0411 code show up for the next 3 years when I sold the car. It's not a difficult job. On a scale of 1 to 10....probably a 5.





I believe Andy Hess has a write-up on it but I can't find the link.

Hope this helps...

JC 96 TT

 

Hi Aircool'd,
P0410 = Secondary air injection system, Signal implausible / Implausible Component Section / Malfunction, MIL (check engine light) is on and Freeze Frame is stored in memory
Here is the 993 code list:
https://993servicerepair.blogspot.co...-for-1996.html
Here is how to investigate the issue:
https://993servicerepair.blogspot.co...-diagnose.html
Andy

 

I did the same project last year on my 1998 C2 with about 80,000 miles. I used the bicycle brake cable method enhanced with CRC solvent. i got a long aerosol can straw on Amazon to get reach all the way up the ports and after doing the Roto-Rooter thing I flooded the ports until the solvent ran clear out of the adjacent ports. The hardest part was getting the manifolds lifted up into their places (I ended up using a floor jack to steady them). I had earlier replaced the SAI valve and the vacuum valve above it. So far no more CEL. The forward-most cylinder on the driver side had heavy carbon built up on the exhaust valve, and I am not sure why just one cylinder was affected. The SAI port on this cylinder was also the most fouled with carbon.

 

You don’t need a top end rebuild. And since you live in SC where there are no emissions tests, you’re good to go. Hopefully you can clear the codes and get rid of the light with your scan tool. I used to put electrical tape over my zenith C2S to cover the light. This may be an indication of valve guide wear, but nothing to lose sleep over. The carbon buildup impacts the emissions, but it has no impact on performance whatsoever.

 

When I did the SAI cleanout, the valve was very dirty and causing the code- the channels were clean- didn't need to do any roto-rooting. Getting the valve off is a PIA- worst part of the job. There's a small vacume line right by the valve- make sure to reconnect- I knocked mine loose and it kept throwing the code until I reconnected it- hasn't thrown a CEL for 5 years now.

 

Hi Prswill,
Yes, the check valve on my car didn't cooperate in its removal either.
How to remove a really stubborn valve is discussed at the bottom of this page:
https://993servicerepair.blogspot.co...horror-of.html
I also found that I only needed to replace the valve to resolve the issue.
Andy

 

The very first stickied post on the subforum talks about this. https://rennlist.com/forums/993-foru...i-circuit.html

But the most helpful post I've seen is this one: https://rennlist.com/forums/993-foru...intensive.html

 

Took the car out for a 30 min drive and CEL suddenly went away. Imagine it comes back, don't think I clicked anything on my ancel OBD to clear anything but let's see. Glad this isn't anything like a top end rebuild, got nervous for a second.

 

Drive and enjoy! Just keep an eye on your oil consumption moving forward.