OBD II Codes, P01188 & P01189

If you look at the way the O2 sensors and cats are configured, Bank 1 is cylinders 1-3 and Bank 2 is 4-6. On a V6, Bank 1 would normally be cylinders 1, 3, and 5, while Bank 2 would normally be cylinders 2, 4, and 6.

If the O2 sensors are original, I would suspect that for this code the front ones (well, all of them, really) to be out of spec by now. They are supposed to be changed at 100K IIRC. (Our 325i has about 110K and I have reset an O2 sensor-related code once but it's been several months and I don't recall what it was now. I plan to replace them this Spring, as it's a bit chilly in the driveway in March.)

You can check the voltage at each sensor (pre- and post-cat) and check each against its counterpart, or swap them all to see whether the problem moves. I don't recall how the voltage compares to lean or rich and I'm not going to look it up now, but it should be easy to find on the net.

Checking the fuel pressure is also cheap. Injector problems show up as misfire codes in my experience, but YMMV.

There is only one MAF sensor, however. Though of course Banks 1 & 2 can vary from each other a little, causing one to indicate a problem before the other does, I would expect a plausability check instead and (probably) a MAF-related code. But as I've never seen one fail yet, I am guessing.

My '00 323i was a problem child. I wish you better luck with yours. (The '02 325i and '04 330i have both been great!)

HTH,

I don't want to sound like I'm arguing with your answer, but I see not point in checking the post-CAT sensors because they would not know that the out-of-range condition was coming from a particular pre-CAT condition. The post-CAT sensor(s) are looking at an exhaust stream where the out-of-range condition of the pre-CAT components is blended. If the pre-CAT O2 Sensors are saying that they can't get the fuel mixture to within whatever the spec is, the post-CAT sensor (s) would be seeing the blended result, and would not know the problem was from Bank 1 or Bank 2. Does that make sense?

I was thinking of an upstream component that would affect both the Bank 1 and Bank 2 O2 Sensors, since they are both claiming they are not happy with the fuel mixture. The upstream sensor, by my thinking, would be the MAF.

I'm a bit confused by the P1188 and P1189 codes because the O2 Sensor(s) already look at the air/fuel mixture to report out of range lean or rich conditions. I don't quite understand why there is a code Fuel Control when the result of fuel control is rich or lean, and the O2 Sensors already monitor this with other codes. How come BMW has unique codes for this when there is already a common code?

PS I drove the car with the scan tool connected, and the P1188 and P1189 codes came up at the same time.

Argue away! Particularly when I'm wrong (which seems the case here).

I misread the very first line in your post, sorry. I thought it said you had an indication for only one bank, not codes for both. Now I see why you're looking upstream. It could still be that the O2 sensors are end-of-life but it's improbable that they would fail at the same time for both banks.

Note that there are two cats, though, each with pre- and post-cat sensors, one cat per bank.

Also upstream are the intake temperature sensor, fuel pressure, and any vacuum leaks.

No idea.

Are you sure? If the MAF needs cleaning, I'd be expecting the engine to run a little lean on (hard) acceleration and, therefore, hesitate or misfire at some point. This assumes you have a hot wire MAF and it's dirty so not being cooled by the air enough so the ECU thinks there's less air entering than there actually is.

I've not heard from many that cleaning a hot wire MAF is always 100% successful. I replace mine when they play up.

Okay, I follow you. My strategy was to look at something that could confuse two O2 Sensors before I looked at the O2 Sensors themselves. I have two different O2 Sensors reporting, so I was thinking there is a common upstream problem that would affect them both.

Vac leaks are an item I had not considered. I do not know if the Fuel Control problem is rich or lean, and a vac leak would certainly feed a lean condition.

The MAF isn't reporting the error. The error report is that the fuel trim isn't correct.

As the motor runs, the O2 Sensors look at the exhaust stream and the computer adjusts the fuel trim (air/fuel mixture) so that the exhaust stream has the correct ratio of unburned fuel and air. The report is that this ratio is not correct, but does not indicate if the problem is a rich or a lean condition. If the MAF was on the fritz, I've been told that this will cause the computer to put in the fuel in the wrong ratio.

I'm only looking to upstream issues that can cause both O2 Sensors to report a Fuel Control error. If there was only one error, then it would easily be the appropriate O2 Sensor, but since there are two errors and the O2 Sensor is an expensive part, I was thinking that a common upstream problem was causing the errors.

If both the pre-cat and post-cat O2 sensors are giving an error code, be careful as a poor mixture can overheat the catalytic convertor's internals and ruin the cat. Quite expensive.

Best regards

David

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That's not happening.

I am getting a P1188 and P1189. These codes translate to FUEL CONTROL, BANK

1 SENSOR 1 AND FUEL CONTROL BANK 2 SENSOR 1.

I have no reports of fuel problems from the post-CAT sensors.

I like to believe that the pre-CAT O2 Sensors would not both fail at the same time -- although this is theoretically possible -- therefore I need a common cause that is upstream. What I have no information about is whether the Fuel Control is too rich or too lean. Knowing this would help to narrow the search for the trouble.

CRAP!!!!

That should be P1188 and P1189.

NO NEED FOR CAPS....

I was warning that if you continue to run with a poor mixture, you are risking the health of the cat.

David

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Sorry, the ALLCAPS was not denoting an attitude problem on my part, just setting off the code description from the rest of the text.

I also pulled P0130 and P0150 that have to do with FUEL TRIM, and P0170 and P0173 that are the O2 Sensor Error. The P0nnn codes are generic that all OBD II cars can have, and the P1nnn codes are unique BMW codes for the same components. So, I now have the same two components each reporting with three different codes the same conditions.

no problem

You say that you ran with a scan tool connected, did you get to see the fuel trims ?

The pre-cat O2 sensors give the ECU feedback on the mixture exiting the cylinders, and then the Long Term fuel trim and Short Term fuel trim values are used to correct the mixture according to those O2 sensor values. The scan tool should be able to tell you if the Trims are rich or lean. I looked at

for an E46 323, it shows there are two exhaust manifolds (headers) each of three branches, and each having their own pre-cat and post-cat O2 sensors. So the scan tool needs to display whether the Trims for Bank 1 sensor 1, and Bank 2 sensor 1 are Rich or Lean.

I know it sounds obvious, but have you checked the plugs and plug wires (HT leads), and believe it or not , the grounds for the engine and ECU. Vacuum leak sounds plausible, too.

HTH

best wishes

David

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I bought the car yesterday for Cheap, and when I get this sorted out I am confident as one can be with a Used Car that it will be fine for a long time to come. The guy I bought the car from is not mechanically inclined at all, so he makes some of the monthly yacht payments for his mechanic.

I'm going to be looking closely at the car today, Saturday, so I should be able to find something out. I used the scan tool on the car while I was driving, not a really smart thing to do, so I haven't looked closely to see what the trims are. Dodging the oncoming cars and avoiding the Toyotas is difficult when distracted by the scan tool ...

Good Luck, I too bought a car cheap that was not maintained properly. I made an error, hope you fare better.

regards

David

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I wouldn't expect it to if it's just a bit dirty. Also, if it's not reporting an error, why was it your "first instinct"?

In a modern car with multiple feedback systems and sensors, air problems can adversely affect fuelling where the fuelling would otherwise be fine.

If your MAF is dirty, the O2 sensor feedback loop will not stop the engine running lean and misfiring and the exhaust gas ratio then being incorrect. I would expect the O2 to report the incorrect exhaust gas though.

"Lean" means to much air in the air-fuel mix, i.e wrong ratio..doesn't it?

The MAF is common and upstream as can be a split hose (mentioned elsewhere)..

Because as an upstream monitor it can give false information to the Fuel Trim decision-tree in the computer that the O2 Sensor sees as a problem with the fuel control in both O2 Sensors.

Lean means too much air or not enough gas, like a cup of water that's partly filled is half full or half empty. It helps to know which way the condition was going when the error got reported.

I can't see any split hoses.

I spent the day working on this, it's time I pay somebody with better tools than I have. I hate when that happens.