zooming993

I've noticed if I allow my car (95) to idle for more then 5 minutes my CEL will come on but after I drive her for a mile or so the light goes out, what causes this?

phoneyman

Since the CEL can be anything, probably best to get a code scanner of some sort and find the actual code. Since its a 95 its not one of those SAI problems. Maybe cat efficiency for cooling? Battery/alternator connection issues? Im out of guesses.

Ponchobroke

When my 95 did that, it ended up being a bad O2 sensor... Replaced it no more CEL.

BobbyT

You can read the codes on your 1995 without a code reader.

1. Turn on the ignition, but don't start the engine.
2. Depress the accelerator pedal fully for about 3 seconds.
3. The CEL will illuminate steady, and then begin to flash.
4. Ease off the accelerator pedal, and read the codes.

Each code consists of four digits, such as 1121. Each digit will be a number of flashes followed by a pause. Example: Flash pause flash flash flash flash flash = 1500, which means "no fault found". There may be multiple codes. You should have a single flash then a pause, then a single or a double flash. If the flash is double then the fault is intermittent (loose contact) otherwise the fault is constant. And then the following flashes;

11 Supply voltage
14 Engine temp sensor 2
15 Throttle potentiometer
18 Rpm signal
19 Speed signal <- Speedometer
21 Hot Film Mass Air flow sensor
22 Oxygen Sensor (Signal)
23 Oxygen regulation
24 Oxygen sensor
25 Intake Temperature Sensor
26 Ignition timing change
27 Opening winding of idle stabilizer
28 Closing winding of idle stabilizer
31 Knock sensor 1
32 Knock sensor 2
33 Control unit faulty
34 Hall signal
36 Idle CO potentiometer
41 Control unit faulty
42 Fuel pump relay (DME-relay)
43 Tank ventilation relay
44 Air Pump
45 Check Engine warning lamp
51 Injection valve cylinder 1
52 Injection valve cylinder 6
53 Injection valve cylinder 2
54 Injection valve cylinder 4
55 Injection valve cylinder 3
56 Injection valve cylinder 5
67 Ground and plug connections
69 Ground and plug connections


A MAF failure would look like;

FLASH pause FLASH pause FLASH FLASH pause FLASH

zooming993

Thanks for the replies Guys. I'll try the accelerator pedal method and see what codes come up.

nine9six

...And the CEL codes are? Inquiring minds want to know...

Aaron 993C2

That is such a convenient way to check fault codes, anyone know why Porsche ditched that feature future on the other years?

Mike J

Too many codes in the ODBII standard - besides that, these days basic code readers are really cheap - I keep a small one in my door pocket.

Aaron 993C2

Ah that makes sense, thanks! I had a CEL last year, turned out to just be a misfire, but I was wishing at the time that I could have checked it with the CEL light itself instead of driving to a shop to use a reader.

996scott

I had an intermittent check engine light that would come on and off every now and then. Replace the O2 sensor and cleared it right up. easy diy for about $100

nine9six

96-98 993s have 4 o2 sensors. 2 before the cat and 2 after; @ 100 ea. for a guess at a bad o2 sensor, is an expensive guess.

Just wait till you read the codes.

ard

Resurrecting a very old thread.

Thanks for the detailed instructions BobbyT. FWIW, I had to reverse steps 1 and 2 below in order to obtain a readout; i.e. I had to:

1. Depress the accelerator pedal fully
2. Turn on the ignition, but don't start the engine
3. Wait for the CEL to begin flashing
4. Ease off the accelerator pedal, and read the codes

sacman

I have a 1996 and it was due to the original flywheel at 95Kmiles.

JPS

So given above, flash, pause, flash flash, pause, flash flash, pause, 4 flashes = ?? (1, 2, 2, 4)

JPS

Bump