ECU's

Clean your Mass Flow Sensor along with the eletrical connections. Maybe also need o2 sensors?

 

You only need to leave the power off for a minute. The ECU's do not have any sort of battery back up or static ram, etc. Just like when you turn your desktop computer off.. when there is no power, it's done. Turning the power off to the car for even 10 seconds probably clears the ECU's, although I generally do it for 60 seconds, just in case any caps have power in them. No need to leave it for hours on end

Ray

 

Yes this is true for resetting the ecu memory however, when the car is restarted it needs to relearn the warm up parameters of the engine. If the engine is still warm the ecus will not properly see all the temperatures. One of the things the ecu's monitor are the coolant temperatures. The ecu's uses the temp to determine weather or not to open the secondary air injection valves, among other things related to emitions. So when you reset the ecu's you do need to let the engine get cold before you let it go through the warm up/relearn process. Failure to do this can cause rough running of the engine.

 

I'll second that motion.

 

I'll third it, especially for the O2 sensors.

 

Interesting, if you read the 355 manual, it gets a bit confusing on this point.....it seems to imply that the engine needs to be at operating temp BEFORE you click it off and do the relearn process...I don't have the manual in front of me, but that was how I interpeted it.

 

That's a very good point and I believe it may actually explain a recent [strange] problem I had on my car. When I was doing some work recently, I cut power to the car for a bit, then turned it back on. I believe the car may have still been warm, although normally when I cut the power it's been sitting over night, so I never really gave much thought to what you mentioned above (again, a very good point indeed).

Anyway, the other week my car had a strange problem where the exhaust note was changing out of the blue. I wasn't able to isolate the problem for sure, but what I suspected was that the secondary air injection valve was opening at the wrong time for some reason. After reading your comments above, I'm wondering if perhaps I cut the power while the car was still warm and threw off the ECU with regard to when to open those valves. If that was the case, it's possible the valve could have ended up open at the wrong time or stuck or something.

Anyway, good point on taking into consideration the temp.

Ray

 

Whenever the battery is disconnected, or whenever power is disconnected from the ECUs, the ECUs lose all their self-learned operating parameters. The ECUs must re-learn these parameters before the car be used again.

To re-acquire these parameters, leave the engine run for about 10 minutes under the following conditions:

1) Car stationary, engine idling.

2) Engine at normal operating temperature.

3) Al electrical power users (lights, windshield wipers, etc.) switched off.

4) Climate control switched off.

This simple expedient enables the engine ECU to re-acquire the necessary parameters, thus preventing engine problems like stalling when idling, and flooding in nose-to-tail queues, etc..

 

Yes this is true, but the engine runs different when it is stone cold. The secondarys are opened up until the coolant temp comes up. If I'm not mistaken, when the engine is cold the ecu's also control the fuel enrichment. This should be especially true of the OBD2 cars with the pre-cat and post-cat O2 sensors. It is all related to the emissions. They want the cats to get up to proper opperating temperature quickly. But then once up to temp, they don't want the cats to get too hot.

So like I was saying, if the car is already at the proper opperating temperature the ecu's can't see the changes in the temperatures from cold to hot. Hence the term "warm up". You can't get an engine that is already warm.....warm. The engine needs to be cold in order to be warmed up. Plus you have the cold start valves that alter the way the engine runs. If the cold start valves are warm, well, then they have no need to adjust he way the engine is running. So the ecu's will miss all of the stuff that goes on when the engine is being WARMED from cold.

SO if you let the car learn the parameters when it is warm, it will get all the warm parameters, but miss all the cold stuff.

The car should be cold.

Capiche.

 

very informative guys!!!!!! lesson learned if I have this problem

 

That's an understatement. LOL!

The stupid manuals are always confusing. They are soooooooo poorly written, it is really sad. That and they are missing loads of stuff.

 

Glad to hear you got it figured out.

 

When talking about an engine being "cold" to reset the ecu what temp is considered cold?

Russell