Ignore Check Engine Light?

[glenndeweirdt]

The check engine light comes on intermittently in my '99 996 w/25K miles. The light comes on for two or three days and then goes away. No noticeable problems when driving. The first time it happened I took it to my local Bosch service center who found no problems (suspected oxygen sensor). It has happened twice more in the past six months.

The car is my daily driver for a five mile commute and occasional errands(thus the water cooled 996). Recently passed emissions test (light not lit at time) with flying colors.

Any reason why I can't ignore this? Any horror stories?

[aigel]

Generally the "check engine" light is a light that comes on if there is an emissions related problem. Say, your 02 sensor is not working properly, or your EGR flow (not sure if applicable in your particular car) is low. So, generally the car is not going to bow up if you keep driving.

However, the emissions related problem may as well be another technical problem. Here an example: You have a occasional misfire on one cylinder, intermittent. That will get the check engine light to come on. Yes, you won't destroy the car, but you may have a more serious problem on that cylinder than just a bad coil. Coolant or oil in your combustion chamber come to mind.

It is not rocket science to diagnose an OBDII check engine light. Go to your next auto parts store or even WalMart and get a simple OBDII reader. It will return a code when the light is on. Let us know the code and I am sure we can help you from there.

Cheers, George

[glenndeweirdt]

Thanks George. I will get the reader and return to the forum with a code. By the way, how difficult is it to change the O2 sensor on these puppies? It was a snap on my '83.
Glenn

[aigel]

Glenn:

I am sorry I can not be of further help. I would think it is not a big job to change the O2 sensor, as it is a service item that has to be changed on a regular basis. You actually will have more than one 02 sensor. With OBDII equipped cars, there is one sensor before and one after every cat. converter. Expecting that the car has 2 cats, you look at 4 sensors.

George

[Bill Verburg]

CEL can also be set off by something as simple as a loose gas cap.

CELs are going to be an ungoing PIA for '96 up cars

[GarryW]

I had a similar problem with my 99 996 right after I bought it 3 months ago. After taking it to a shop, diagnosing O2 sensor problem, and a porshce dealer, diagnosing mass airflow sensor malfunction (they wanted to change it for $500). I had conversation with a friend at the track with a 996, who had also had the same problem. We put his code reader on it, cleared the CEL, cleaned the MAF (5min) and the light has not come on again after 2,000 miles. I have done a search on the board and was surprised I saw nothing about this problem with an easy fix. Hope this helps.....Garry

[ZX9RCAM]

I can't answer the actual question, but if the CEL is flashing, as
opposed to constant, you are supposed to pull over (per the manual).

- Cam

[TJ78]

I posted a seperate topic about my oil pressure and Check Engine Light. The Oil pressure question got taken care of quickly. The Check Engine Light feedback was to go to an auto parts store and get the code read.

I've done that.

Does anyone know of a website or a document that lists what the codes are?

I forgot the code already (or else I'd post it here), so I'm going to have to go back to the auto parts store.


If anyone can point me to a list of definitions for all possible codes, I'd be forever grateful!


Thanks, TJ

[glenndeweirdt]

Your reader should have the code definition. Did you reset the check engine light? If so, it should come on again in about 40-50 cycles according to OBDII protocols. I have all the proprietary Porsche manufacturer's codes if needed.

[bill3667]

Originally posted by glenndeweirdt
The check engine light comes on intermittently in my '99 996 w/25K miles. The light comes on for two or three days and then goes away. No noticeable problems when driving. The first time it happened I took it to my local Bosch service center who found no problems (suspected oxygen sensor). It has happened twice more in the past six months.

The car is my daily driver for a five mile commute and occasional errands(thus the water cooled 996). Recently passed emissions test (light not lit at time) with flying colors.

Any reason why I can't ignore this? Any horror stories?

While attaching a code reader and finding out the actual cause of the CEL is the best idea it would not supprise me if the cause was due to charcoal canister vapor issues since your commute is so short. I would suspect after you drive the car for a longer distance the vapor issues resolve themselves which is why the light goes out. I had this problem on my '03 Tahoe, took a 100+ mi. trip and it cleared up.

There are many things it COULD be, inc. the gas cap loose, so get the reader and post which error comes up.