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 ˝ 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.
Last edited by 993BillW; 12-24-2014 at 01:38 PM.