BMW: e36 OBDii/SAI readiness not setting - Resolved
09-23-2011, 09:25 PM
#1
Race Director
Thread Starter
BMW: e36 OBDii/SAI readiness not setting - Resolved
Posted this on a couple of BMW forums but so far only responses are of the basic stuff that I already know. Hopefully someone here has experience with this on BMW e36's.
I'm pretty familiar with the OBDii system and the need to "set" the Readiness Flags before the OBDii system will start it's monitoring. I have both a generic OBDii Tester and the Peake BMW Fault Tester.
Background: My '97 BMW M3 was throwing EVAP errors, I knew what the problem was, the EVAP container above the right rear wheelwell had a leak. After replacing the EVAP container I reset the monitoring system and expected the Readiness Flags to set pretty quickly as they have in the past. Most did (the O2 Sensor heater was the last to set) but the SAI Flag still hasn't set (I've done about 8 drive cycles so it should have set by now).
Last winter the SAI pump was squealing like a banshee (bad bearing), left it alone until this problem popped up so this month I went ahead and replaced the SAI Air Pump (with a rebuilt pump, it is working fine) and a NEW SAI Check Valve. However even after 8+ drive cycles the SAI Readiness Indicator still hasn't set, all the rest of the indicators are set. I can hear/feel the pump working fine, it shuts off (as it should) after apx. 2 min.
The only things I can think of that would cause this problem on this car is a vacuum leak or the solenoid under the intake manifold or the check valve on that vacuum line. Is there something else I should be looking at? I'm due for emissions inspection by the end of the month but know it won't pass with Readiness Indicators not set.
With the Porsche 993's this problem usually indicates clogged SAI ports through the heads but don't think that is a problem on the BMW's.
I'm pretty familiar with the OBDii system and the need to "set" the Readiness Flags before the OBDii system will start it's monitoring. I have both a generic OBDii Tester and the Peake BMW Fault Tester.
Background: My '97 BMW M3 was throwing EVAP errors, I knew what the problem was, the EVAP container above the right rear wheelwell had a leak. After replacing the EVAP container I reset the monitoring system and expected the Readiness Flags to set pretty quickly as they have in the past. Most did (the O2 Sensor heater was the last to set) but the SAI Flag still hasn't set (I've done about 8 drive cycles so it should have set by now).
Last winter the SAI pump was squealing like a banshee (bad bearing), left it alone until this problem popped up so this month I went ahead and replaced the SAI Air Pump (with a rebuilt pump, it is working fine) and a NEW SAI Check Valve. However even after 8+ drive cycles the SAI Readiness Indicator still hasn't set, all the rest of the indicators are set. I can hear/feel the pump working fine, it shuts off (as it should) after apx. 2 min.
The only things I can think of that would cause this problem on this car is a vacuum leak or the solenoid under the intake manifold or the check valve on that vacuum line. Is there something else I should be looking at? I'm due for emissions inspection by the end of the month but know it won't pass with Readiness Indicators not set.
With the Porsche 993's this problem usually indicates clogged SAI ports through the heads but don't think that is a problem on the BMW's.
Last edited by Slow Guy; 09-30-2011 at 11:29 AM.
09-23-2011, 09:31 PM
#2
Instructor
The E36 SAI dumps the air directly into the exahust manifold, not the head. It's a bit more forgiving in that sense when you compare it against our 993s. I bet the 993s would have been better off with a similar SAI dump into the manifold instead of the heads. Note the BMW M5 (E39) has simialr SAI port issues to our cars due to the port being in the head behind the exhaust valve. Gee, is there a theme here? There are issues of this cropping up from time to time on other BMWs, but most of the major culprits have already been addressed by you. Typical problems are the pump going bad (due to excess moisture from a failed valve) or a failed valve. The manifold can also get clogged, but it's a bit easier to clear up when compared to our cylinder heads.
Based on your description, it sounds like everything is working as it should except for the readiness set. Have you done the BMW drive cycle to help set them? That portion is a PITA, just like our cars.
Based on your description, it sounds like everything is working as it should except for the readiness set. Have you done the BMW drive cycle to help set them? That portion is a PITA, just like our cars.
09-23-2011, 09:42 PM
#3
Race Director
Thread Starter
Thanks Dave, yes, I've seen the layout of the plumbing into the exhaust and just don't see that as being a problem. It's a pretty big pipe to get clogged although I may go ahead and pull the SAI valve and runn come compressed air through there just to be sure, but I doubt that is the culprit.
I'm fortunate to live in an area where running the BMW Drive Cycles is REALLY easy. I have 2 routes that I can run it from my house. I've done the full pattern at least 4 times now. But, I don't know the e36 cycle like I know the 993 cycle, but I suspect the SAI flag should set after the first 2 min. of running time, the SAI system doesn't run after that. I really believe that flag should be setting pretty quickly, not having to wait for other systems to set first.
FYI, This is the post I wrote up on the 993 Readiness indicators
I'm fortunate to live in an area where running the BMW Drive Cycles is REALLY easy. I have 2 routes that I can run it from my house. I've done the full pattern at least 4 times now. But, I don't know the e36 cycle like I know the 993 cycle, but I suspect the SAI flag should set after the first 2 min. of running time, the SAI system doesn't run after that. I really believe that flag should be setting pretty quickly, not having to wait for other systems to set first.
FYI, This is the post I wrote up on the 993 Readiness indicators
09-30-2011, 11:37 AM
#4
Race Director
Thread Starter
After doing more research I suspected the most likely cause was the O2 Sensors. Assuming the "upstream/pre-cat" sensors were most likely the ones that detected the additional SAI airflow I replaced those (on the M3 there are 2 exhaust manifolds so 2 sensors on each the pre and post cat).
After doing an oil change (unrelated) and replacing the pre-cat sensors it only took 1 drive cycle to set the SAI RI and complete the OBDii cycle. All 8 sensors are set and tester shows "Done" w/ no errors. And just in time, last day to renew the registration w/out a penalty.
After doing an oil change (unrelated) and replacing the pre-cat sensors it only took 1 drive cycle to set the SAI RI and complete the OBDii cycle. All 8 sensors are set and tester shows "Done" w/ no errors. And just in time, last day to renew the registration w/out a penalty.
