dmwallace

I've been doing these steps for my '97 993. Worked again a few weeks ago after a dead battery for a few months.

1. I let the car idle before driving for about 5-6 minutes with the heat on, after reading through a readiness code document I found on a P-car site (can't remember which one). I kept the heat on low throughout the drive cycle.
2. I drove the low speed part of the drive cycle for about 15 minutes, keeping it < 2000rpm and < 30mph. I did have some stop signs, stop lights, etc. during that period.
3. I drove the high(er) speed part of the drive cycle for about 30-40 minutes, keeping it < 3000rpm and < 60mph. Depending on traffic speed I was either in 4th or 5th gear for most of the trip.

At the end of the drive cycle I let the car idle for a few minutes in the driveway before checking the OBD tester with a successful outcome.

SwayBar

For my 96 C2, I've been doing the drive-cycle for years now, and it always clears on the first attempt.

The key is to find an area where you can drive EXACTLY as the cycle states.

e9stibi

It depends on the ECU. I have a 993 that clears after the first cycle and one that needs two. I have done this 10 times for both cars and I always get the same result. However, the cycle works!

71-3.0-911

First attempt? Wow. My 96 takes 3.

Lorenfb

He didn't indicate whether two of the three trips were completed before he started the third trip, did he?

71-3.0-911

I think he did.

"it always clears on the first attempt."

Lorenfb

He needs to be more explicit, e.g. how he determined that only one trip was necessary, so others on Rennlist can benefit too.
Surely you and others would find that a significant insight, right?

SwayBar

Yes, good point - here's what I do:

After winter, I charge and then reconnect the battery.

I retrieve my drive-cycle instructions from the glove box.

I hook-up my OBD reader to look at the failed readiness codes.

I then drive and follow the drive-cycle exactly to the letter, while the OBD reader is still hooked up.

At the end of the drive-cycle when I pull-in to stop, immediately upon stopping, the OBD reader reports that all readiness codes have cleared. Afterwards, I get the car smogged, and they give me my year-sticker for my plates.

This happens every time without fail, and I've never had to do more than one run in 15+ years.

An Important Note:

For all this to happen, I had to first fix my SAI system, as well as replace two 02 sensors - the OBD reader codes told me exactly which ones needed replacement. Once the hardware was fixed, I've had zero problems resetting the readiness codes.

Lorenfb

Based on what you have just indicated, your DME ECU is NOT a '96 DME ECU, but either from a late '97 or a '98 993.

gmorat

After owning a 96 that always had an issue with it's readiness codes and was a pain to get them set I always dread Smog tests in CA.

I got a notification to go to a Star center for this latest test and the hairs stood up on the back of my neck.

Anyway, hooked up my ODB reader and ensured no codes and readiness flags all good and then went and got a non-recorded pre-test which I passed and immediately afterwards the full test to the same result.

Now I just have to pay the crazy registration fee and not worry about smog testing for another 2 years.

What a relief!

G

71-3.0-911

I decided to be done with setting the flags and just bought one of these. Now when I change the battery every 4 years or so, I don't have to complete the drive cycle again.

Schumacher OBD-L Memory Saver Detector

SwayBar

Interesting - I know that you know your stuff...

Is there a way I can identify which ECU I have? If I remember correctly, my car was built May 1996.

Lorenfb

You can use a Porsche tester, e.g. Hammer/PST2/PIWIS, to determine the ECU's part number, or you can attempt to read
the actual part number on the ECU under the driver's seat. The protective cover over the ECU & the immobilizer will
most likely need to be removed.

Robert Collins - 96 993TT

Random OBD II system question guys...we accidentally left one of the O2 sensors (post cat) out and after driving for a bit it triggered the check engine light. All other codes are set and passing except for the Left bank 1-3 O2 sensor.

My question is, will drive cycles like the BMW test allow for this one code to reset and therefore the light goes out, OR do I have to reset all codes and start over? I'm planning to do the drive cycle this weekend with the light still on unless someone here knows that is a complete waste of time.

Thanks in advance!

beagling

This works. I did 6 attempts (3 drive cycle pairs) with the BMW Drive cycle and that never worked.

I used this sequence and it worked. First time!

I did first cycle at 5AM . Parked it for 4-5 hours then did my second cycle. PASSED .

plima007 thank you for this.