Experiment w/ OBDII Readiness Indicators (long)
 

About 4 mos ago I disconnected the battery on my ’97 993 for some routine maint. and other work. After reconnecting the battery I decided I wanted to try an un-scientific test of the OBDII Readiness Flags. I decided I would drive the 993 as I normally would for a few months until just before it was time for me to renew the registration which in TN requires an annual emissions test (no sniffer, just pass the OBDII tests). Since in the past I’ve never had any problems using the so called “BMW OBD ii Drive Cycles Procedure” to get my readiness indicators to set I wasn’t too worried about having any issues.

The Code Reader I use is the INNOVA 3100 and I’ve had it for several years, I think I paid less than $100 for it. The only time I’ve had a problem with it was caused by operator error (me) when I failed to disable the Immobilizer and the reader couldn’t communicate with the car. I learned that lesson the hard way.

I don’t know how many miles I put on before I hooked up the tester to check (remember I said un-scientific) but it had to have been in excess of 1500 mi. I drove the 993 as I normally would which includes regular excursions above 5k+ RPM. I did not try to baby the car for the sake of this test.

When I hooked up the OBDII Reader today I was not surprised that only following (3) Monitors (Readiness Indicators) were set:

M - Misfire
F - Fuel System
CC - Comprehensive Component

The following (5) Monitors were in a Non-set (flashing) condition:

C - Catalyst
EV - Evaporative System
2A - Sec. Air System (SAI)
O - Oxygen Sensor
OH – Oxygen Sensor Heater

There are a total of (11) Monitors but as the OBDII Reader’s Manual says “not all vehicles support all 11 monitors”. I deduce the Porsche supports only 8.

After performing the “BMW OBDII Drive Cycle Procedure” the first time on Sat. morning and returning home the status of the monitors had not changed, 3 were still set and 5 were flashing (not set). It should be noted that I left the OBDII Reader connected to the OBDII port the entire time while I was driving, once a minute or so the Reader would “refresh” (ping the 993”s OBDII system) itself. At no time did any of the Readiness Indicators change their status during or after the first run.

After letting the 993 sit (cool) for about 4 hrs. I decided to try the second run (in the past I let the car sit overnight, not this time). I went on a slightly different route but it still allowed me to run the “BMW OBDII Drive Cycle Procedure” in order. All through the drive the Reader was still connected to the car and there was no change to the 3 set/5 flashing status until I got home. I backed into the driveway and pulled the handbrake to complete the final step which is “Idle for apx. 5 min.” (in-gear for auto transmission cars only). After less than 1 ½ min. of idling the 5 remaining Readiness Indicators set (all on solid, none flashing)! Success! In the words of Jackie Gleason “How sweet it is!”

To be clear I was rarely able to complete any individual step of the “BMW OBDII Drive Cycle Procedure” without a break for a stop sign or to go around a corner, I would just return to the speed and RPM I was moving in as soon as possible. I did however extend the drive on that step of the procedure for as long as that section of road allowed (without getting ridiculous). However it is critical that you not exceed 3K RPM or 60 MPH for the duration of the test. I did however, on 2 occasions exceed the 3K/60 MPH limit but not by much and it was for a very brief period of time so I don’t think that is a “hard and fast” rule, just try your best to avoid it.

I have photos of the Reader connected and the display that I will upload tonight.

Someone (I don’t remember who) wrote out the “BMW OBDII Drive Cycle Procedure” so we didn’t have to use the PDF file, hopefully they won’t mind if I copy it and put it in this thread. Save me some more typing.

Hope this helps.

You cannot see that in the first photo the monitors C, EV, 2A, O and OH are flashing but they are. You'll also notice "DONE" in the second photo, this did not happen until the last 5 monitors had set.

This thread is an oldie but a goodie as I had basically this exact experience last night.

After cleaning out my SAI ports and clearing all related codes, I needed to get the monitors reset in preparation for getting my NJ inspection sticker (OBD2 port read only).

For reference, the "BMW Drive Cycle" is:
1. Start engine, let idle for approx. 2 min, 10 secs.
2. Accelerate to 20-30 MPH, Maintain steady speed for approx 3 min, 15 secs.
3. Accelerate to 40-60 MPH, Maintain steady speed for approx 15 mins.
4. Idle in Neutral for 5 mins. (manual trans.)
(Note: must remain below 3000rpm and 60mph during the duration of the test)

I mapped out a route that entailed about 10 min of 25mph driving, well above the 3m recommended by the cycle for step #2. That would bring me to a network of long, straight stretches of 45-50mph roads for step #3. Then back the way I came and finishing step #4 by idling in the driveway.

Like 993BillW, after my first run on Sunday night, there was no change in any of the monitors. I re-ran the cycle again last night, and with the increased traffic on a weeknight adding some interruptions, and with once or twice where I got a hair over 3000rpm, I figured this test was a no-go. Much to my delight when I hooked up my scanner while idling in the driveway for step #4, it showed all monitors as "ok". As Edd China would say, "result!"

My interpretation of this is that the drive cycle is not as exact as it would initially seem. I never had 15 uninterrupted minutes of 45-50mph driving, so there's definitely tolerance for a stoplight or two. I think the objective is to get enough data in total for each of the steps, and keep things smooth and steady throughout. This is definitely "grandma driving"; the fun driving can come later.

That's because there is no correspondence between engine load (which the Porsche drive cycle is based on) and road speed, which the BMW requires.

I know for a fact that you can stop at signs and traffic lights during the drive cycle. I managed to set my readiness codes after a CEL light reset (misfire) in two days and three drives. Basically, I do the entire "BMW drive cycle" but I don't worry about stops.

I did the slow part around my neighborhood, stopping at all stop signs. Then I did the 40-60 part by going back and forth on Foothill Expressway which has a 45mph limit and stop lights spaced about a mile apart. I don't know why it took three drives but I suspect I didn't let the car cool off enough between the first two drives which I did on the same day.

I suspect the stops actually help because the car needs to see varying RPMs and loads during the drive. I upshifted way sooner than I normally do to hit the lower RPMs.

I cringe when I read about guys going 45-55 in the right lane of their local freeway with cars wizzing by at 70.

Two years in a row I carefully followed the drive cycle and my codes reset before getting to the idling portion.

Engine and road speed are easy. What's the best way to know how much load you're applying/demanding?

Does the 'ms' (milliseconds?) range in the drive cycle procedure pertain to injector duty cycle?

Bosch Hammer or PST2 or PiWiS or Durametric

yes

For more info, read here under "Porsche 993 Cycle Flag Basics: http://www.systemsc.com/codes.htm

1. With access to a Porsche tester, setting the monitors takes about 30 - 45 minutes.
2. Again, '96 vehicles require three trips, i.e. without a tester, 3 cold starts
for the SAI monitor
3. Setting the O2 sensors monitor & the CAT monitor are the most time consuming.

sky: What times/day were you on Foothill? Y&ou are correct about RH lane, even after midnight on a Sunday nite.

Downtown Porsche Los Angeles charged me $150 to get the OBD II to ready mode. Worth every penny!