Hi everyone. So here's a loaded question. Keep getting 1212 and 12111. With a dash of 4122 here and there but never consistently. Idle slightly rises, then settles off and on. After driving it she settles right down and purs at 8-900 rpm at idle. Any thoughts?
What car? 4122 is cats too hot. 1212 and 1211 is lambda, basically ecu is not able to regulate the fuel mixture, could be few things, O2 sensor or thermocouples are easy to replace. After that it could be FPR, injectors or even MAF. Run searches for 1212 and 12111 lots of information.
Thermocouple? I removed the MAFs and cleaned them. Put them back on, cleared codes and it ran great for a few drives. Went to start it this morning and the CEL came back on with the 1212 and 1211.
Do you have an OBD2 reader which looks at fuel trims and O2 readouts? 1212 "Multiplicative value for self-adaptation Lambda regulation" 1211 "Additive value for self-adaptation Lambda regulation" 4122 "Catalyser temperature ECU" 4122 may not be related to the others. I don't think it's an overheat problem. If you're not getting a Slow Down light and a 4121 code, the Motronics ECU may be identifying a fault with one of the thermocouple ECUs (perhaps producing an out-of-range signal... i.e. a temperature which is not physically possible). Regarding 1212 and 1211 Here are some good videos on analysing fuel trims: The videos may help you identify which component is actually faulty instead of replacing random components. Generally: (Found with Google) Additive Fuel Trim "Add" means additive trim, which is addressing an imbalance at idle. When the ECU is using additive trim, it is telling the injectors to stay open a fixed amount longer or shorter. The malfunction (e.g. vacuum leak) becomes less significant as RPM increase. For additive adaptation values, the injection timing is changed by a fixed amount. This value is not dependent on the basic injection timing. This is the boring Bosch definition for Additive Trim. It does however tell us quite a bit about this mixture control strategy. Let’s look at a few things. Additive Fuel Trim is mostly used at idle. It is stored in the DME [ECU] for start up, that makes it a Long Term Fuel Trim. Additive fuel trim has the most influence at idle range loads, but it is also used off idle for minor trimming adjustments. The term additive is used because of the way fuel is added to the mixture. if the base fuel injection time is 3.0 millisecond and a change is needed, it is made by adding a fixed number. For example 0.1ms or -0.1ms. Not a percentage based amount like generic fuel trim. Multiplicative Fuel Trim "Mult" means multiplicative trim, which is addressing an imbalance at all engine speeds. The malfunction (e.g. clogged injector) becomes more severe at increased RPM. For multiplicative adaptation values, there is a percentage change in injection timing. This change is dependent on the basic injection timing. That is once again, Bosch's definition of multiplicative trim. Multiplicative is a percentage based adjustment made at part load engine load ranges. It is also a Long Term Fuel Trim like Additive, and used at start up as well. If Additive and multiplicative are both long term fuel trim, where does the short term, or here and now happen. This can be seen in oxygen sensor feedback. You can use this to view the short term correction in manufacturer specific fuel control when Additive and Multiplicative fuel trim are used. Doesn't the 348 have two CELs? If the fault is only on one bank, then you could try interchanging components.
Wow, great amount of info and thanks for this. Yes the 348 has 2 CEL lights. One for each bank. That's the next step is to start swapping mafs and o2 sensors from side to side i hate the idea of just throwing parts at the car too.
multiplicative often turns out to be a bad MAF and multiplicative happens over time. I assume you get it on one bank only? Try swapping mafs from side to other side.
I'd would new O2 and thermocouples and then swap the MAF's. Those parts are probably due anyhow. I bought them online for like $75 a piece actual Bosch units wit the same plug and all. Your 4122 is possibly thermocouple, cat ecu (probably not) or cat itself.
You have OBD1. The fuel trim live numbers cannot be observed with a OBD2 scanner. The 348 thermal protection ECU does not work the same way as the one on the 355 and can be unplugged for troubleshooting. Codes 1211 and 1212 are often thrown up when the MAFs are at borderline. Some of the swapping suggestions above are where you should start to isolate the issue.
I cleaned the MAFs. Put them back on, went for a drive, all good. Woke up the next day. Codes came back on start up. I'm going to try the battery shut off and on again. Then start swapping stuff side to side.
Yup i did. It is currently sitting with cleared ecu (bank 1-4) and hasn't been started since i cleared them. I"m going to do a battery disconect/reconnect via the cut off switch, then start it to see if the "relearning" process does anything.
I did it. CEL light didn't come on at start up. Waited for the fans to kick in. The idle was going up approx 100rpm, then down, then up and down. Then it just settled at around 900rpm. I'll have to drive it for a bit to see what happens.
FYI, that's what mine did only when starting when cold. It would surge up then drop to like 400 then back up and down and settled at 900 after a few minutes. Exactly like a bad IAC valve. Not saying that your issue just passing it on. Everyone says the cam sensor works or fails instantly it does not go bad. Nope it can go bad bad slowly.
Idle Air Control valve., it control the amount of air flowing into your engine so your vehicle's computer can match it with the correct fuel. You have one on each bank. That can be cleaned out btw.. Google for cleaning video of them it can help as some get gummed up. Image Unavailable, Please Login
