B8 S4 MAP Sensor Code (P012B 00) - can't find the problem

[Salvage_B8_S4]

Hello,

My 2012 Audi S4 is throwing a P012B 00 (Turbocharger/supercharger inlet pressure sensor - implausible signal) and running like shit after a cold startup. It throws a CEL and the idle surges, throttle response is terrible, the exhaust note is very different, its down on power, and car runs insanely rich causing the exhaust manifolds to get very hot, and the MPG is atrocious. Shut off car, wait all of 30 seconds, and re-start the car, and it runs fine (CEL is still on but status switches to intermittent). This all started happening after I cleaned my 034 Intake filter for the first time. (I am on a Stage 1 Tune, for 93 octane, with an 034 cold air intake). I have VCDS as well. This is the only code the car has thrown.

I pulled all 3 MAP sensors (one at back of supercharger, after throttle body, and then one on each the left and right bank of the supercharger) and cleaned them with MAF cleaner. They were a little dirty and kind of oily. I thought I might've over-oiled my air filter so I re-washed it with warm soapy water, let it dry out thoroughly, and am currently running it dry (no oil on the filter). I also cleaned intake tube and throttle body. Put the MAPs back in and the problem seemed to go away for maybe 2-3 days. It came back under the same circumstances, cold start on a warm & humid day (75°F)

Replaced all 3 map sensors with Bosch replacements and ran into the same issue after 2-3 days of normal driving. Need to get to the bottom of this because the exhaust manifolds and cats will eventually get so hot that something will get damaged.

Does anyone else have experience with this code, and what fixed it? Am I getting excess oil in my intake which is fouling up the sensors? Perhaps PCV failure (I replaced it 15k miles ago)? Is it a wiring issue? I'm at a loss right now.

[Smac770]

P012B
Turbocharger / Supercharger Inlet Pressure Sensor "A" Circuit Range / Performance

Charger inlet pressure rationality check
• pressure difference in cross check between boost pressure sensor 1/2; IM pressure, ambient press sensor > 7 kPa
• pressure difference in cross check between boost pressure sensor 1/2 and charger inlet pressure (1) > 12 - 27 kPa

Check the Intake Manifold Sensor -GX9- .

Thanks Audi, clear as mud. "charger inlet" is pointing to the sensor in the back, as the other two sensors are on the charger outlets to bank 1 and bank 2. Why it's saying to check the charger outlet bank 1 sensor, no idea.

But the code seems to trigger based on some kind of relational issue between the three pressure sensor values. So probably best to do some logging of those and try and assess if they seem to become out of spec at some point. Maybe some issue with the air pressure value compared to the ambient value it presumes when the engine is idling.

The pressure value and the temp value from those sensors appear to be pretty basic voltage signals. 5V and ground supply to the sensor, then a 0.4-4.7v output for pressure (0.40v at 20 kPa, 4.65v at 250 kPa).

"for this reason, all senders are validated after the ignition is turned on", so looks like it tests the readings between the sensors on ignition on. But the P code is a "something is wrong involving these things", not a direct pointer to the problem. Are the temp readings rational, just the pressure readings are mismatched? Maybe wiring issues.

[BrokeBichB8]

Whats the full code on VCDS? There are parameters associated that can usually help direct.

[Salvage_B8_S4]

Whats the full code on VCDS? There are parameters associated that can usually help direct.

Here is the freeze frame data for the P012B00 Code. I don't have the full auto scan, as I'm just rewriting from a picture on my phone.

Turbocharger/Supercharger Inlet Pressure Sensor
P012B 00 [172] - Implausible Signal
MIL ON - Intermittent - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 3
Mileage: 128430 km
Date: 2024.06.13
Time: 19:12:31
Engine RPM: 2033.00 /min
Normed load value: 26.7 %
Vehicle speed: 43 km/h
Coolant temperature: 88 °C
Intake air temperature: 34 °C
Ambient air pressure: 1000 mbar
Voltage terminal 30: 13.507 V
Unlearning counter according OBD: 40
Engine speed: actual: 1792 /min
MAP 1_ENVD: 562.50391 hPa
MAP_2_ENVD: 562.50391 hPa
PDT_ENVD: 413.91797 hPa
AMP_ENVD: 1002.9551 hPa
RFP_AV_ ENVD: 71.1024

So I Take it MAP 1 & 2_ENVD are the charge pressure sensors on the supercharger, PDT_ENVD is the Supercharger inlet pressure sensor, and AMP_ENVD is the ambient pressure sensor (1000 hPa is atmospheric/ambient pressure) ?

If that's the case, and we look at what Smac770 shared:

Charger inlet pressure rationality check
• pressure difference in cross check between boost pressure sensor 1/2; IM pressure, ambient press sensor > 7 kPa
• pressure difference in cross check between boost pressure sensor 1/2 and charger inlet pressure (1) > 12 - 27 kPa

The difference in pressure between MAP 1/2_ENVD and AMP_ENVD is 149 hPa, or 14.9 KPa, which appears to be in the appropriate range for the cross check between the sensors. Unless I have something wrong.

[Smac770]

My complaint at the moment would be the apparent complete lack of understanding of the ENVD variables. They do not appear to be the live measured values. Are they diagnostics test result variables? Are they key on measured values recorded for comparisons? There's no ENVD in the Bosch MED variables, and almost none in the Simos 16 of the B9 CYMC. But that could be due to one complaint I have with VCDS labels, they remove the software variable name when they put in a wordy text label. Makes it hard to relate measuring values to variables in proper technical documentation. But it doesn't seem anyone has any proper technical documentation of Simos 8.4 or 8.5 for the supercharged engines.

ENG101388 Intake manifold pressure: absolute 322.05 297.18 hPa

ENG101499 map 330.84 303.31 hPa
ENG103166 MAP_ENVD 0.0000 0.0000 hPa

ENG102680 MAP_1_MES 328.85 305.97 hPa
ENG99737 MAP_1_MES_BAS 321.14 307.62 hPa
ENG102949 MAP_1_ENVD 557.19727 557.19727 hPa

ENG102281 MAP_2_MES 325.95 313.43 hPa
ENG104243 MAP_2_MES_BAS 320.31 305.39 hPa
ENG102960 MAP_2_ENVD 551.89063 551.89063 hPa

ENG99319 Ambient pressure 976.69 975.61 hPa
ENG101830 AMP_ENVD 976.4219 976.4219 hPa

ENG101106 PDT_ENVD 557.19727 557.19727 hPa

ENG99738 RFP_AV 63.96 59.14 °
ENG103313 RFP_AV_ENVD 64.4882 64.4882
ENG101571 RFP_SP 63.42 59.47 °
ENG102212 RFP_SP_ENVD 64.4882 64.4882

Above are some samples of data from maps with the engine idling, cold start vs warm start I believe (vs cold start then after warmed up). Not my data; I don't have a 3.0T to test.

So what is MES vs MES_BAS vs ENVD? SP = specified; AV = actual? PDT = ? The freeze frame data values listed are the ENVD ones, but we have no assurance they are relevant to the actual math of the P code. And the Audi documentation is, as usually the case, almost useless.

What's curious is the only values around that 55x mark in the blockmap are MAP_1_ENVD, MAP_2_ENVD, and PDT_ENVD.

And then there's a single value for what appears to be some "difference of ambient vs MAP", but why record that?
ENG125298 PRS_DIF_AMP_MAP_DIAGCPS 628.93 669.72 hPa


In your freeze frame values, your two MAP ENVDs are similar, but the PDT one is quite different. The P code is because something was "too different", but specifically what, not sure we can know with only the documentation we have.

(the forum removes all white space formatting for whatever reason, so your stuck having to read the table as the forum engine insists)

[Salvage_B8_S4]

My complaint at the moment would be the apparent complete lack of understanding of the ENVD variables. They do not appear to be the live measured values. Are they diagnostics test result variables? Are they key on measured values recorded for comparisons? There's no ENVD in the Bosch MED variables, and almost none in the Simos 16 of the B9 CYMC. But that could be due to one complaint I have with VCDS labels, they remove the software variable name when they put in a wordy text label. Makes it hard to relate measuring values to variables in proper technical documentation. But it doesn't seem anyone has any proper technical documentation of Simos 8.4 or 8.5 for the supercharged engines.

ENG101388 Intake manifold pressure: absolute 322.05 297.18 hPa

ENG101499 map 330.84 303.31 hPa
ENG103166 MAP_ENVD 0.0000 0.0000 hPa

ENG102680 MAP_1_MES 328.85 305.97 hPa
ENG99737 MAP_1_MES_BAS 321.14 307.62 hPa
ENG102949 MAP_1_ENVD 557.19727 557.19727 hPa

ENG102281 MAP_2_MES 325.95 313.43 hPa
ENG104243 MAP_2_MES_BAS 320.31 305.39 hPa
ENG102960 MAP_2_ENVD 551.89063 551.89063 hPa

ENG99319 Ambient pressure 976.69 975.61 hPa
ENG101830 AMP_ENVD 976.4219 976.4219 hPa

ENG101106 PDT_ENVD 557.19727 557.19727 hPa

ENG99738 RFP_AV 63.96 59.14 °
ENG103313 RFP_AV_ENVD 64.4882 64.4882
ENG101571 RFP_SP 63.42 59.47 °
ENG102212 RFP_SP_ENVD 64.4882 64.4882

Above are some samples of data from maps with the engine idling, cold start vs warm start I believe (vs cold start then after warmed up). Not my data; I don't have a 3.0T to test.

So what is MES vs MES_BAS vs ENVD? SP = specified; AV = actual? PDT = ? The freeze frame data values listed are the ENVD ones, but we have no assurance they are relevant to the actual math of the P code. And the Audi documentation is, as usually the case, almost useless.

What's curious is the only values around that 55x mark in the blockmap are MAP_1_ENVD, MAP_2_ENVD, and PDT_ENVD.

And then there's a single value for what appears to be some "difference of ambient vs MAP", but why record that?
ENG125298 PRS_DIF_AMP_MAP_DIAGCPS 628.93 669.72 hPa


In your freeze frame values, your two MAP ENVDs are similar, but the PDT one is quite different. The P code is because something was "too different", but specifically what, not sure we can know with only the documentation we have.

(the forum removes all white space formatting for whatever reason, so your stuck having to read the table as the forum engine insists)

Yes I agree, the labels and variable names of the VCDS measuring blocks are very annoying, and documentation on the 8.4/8.5 Simos is limited. Perhaps the VCDS wiki has some kind of list that relates their wordy names to the variables listed in Audi's documentation. And you're correct, we have no idea what variables are actually related to the rationality check of the P012B00 code. The fact that the freeze-frame data chooses to show you the ENVD values must mean they're relevant in someway, but we do not know for sure. Maybe I'll post this in the RossTech forums and see if anyone over there as a clue as to the relevancy of the ENVD values. But thank you for the sample data.

I've been able to gather more understanding of these variables from another forum. https://forums.audirevolution.net/t/...logging/6086/5

It appears that your suggestions were correct:
AV - Actual value
SP - Setpoint
ENVD - Environmental data (still a little unsure of what that actually means, and how is it different from AV or MES?)
RFP - Recirculation flap (reported in degrees, I think this is the boost regulating flap at the back of the supercharger, right after the throttle body)

Ones I'm unsure of:
MES = measured value?
BAS = Baseline value (what the ECU is being told to target?)
AMP = ambient pressure?
PDT = no freaking clue? Perhaps "Pressure Difference Target" Just throwing things around here.


Perhaps "MAP" and "MAP_ENVD" are for the supercharger inlet sensor, and MAP 1 & MAP 2 are the charge pressure sensors because there are two of them.

Comparing the sample data to mine, The MAP 1/2 ENVD's are very similar. The AMP_ENVD's are about 25 hPA difference, which is probably attributed to environmental differences, assuming AMP = ambient pressure. Ambient pressure at sea level is 1013 hPa (I'm at sea level), but it's roughly 970 at 1000 ft above sea level (matches sample data). My PDT_ENVD is roughly 144 hPa lower than the sample data (that's a pretty big difference), and my RFP_AV_ENVD is roughly 6 degrees greater.

So, based on my freeze-frame data , I don't see much of a difference between the sample values you provided.

Instead of relying on the freeze from data, perhaps the better approach is to try and log/live-monitor those measuring blocks during cold startup, driving, and warm startup to try and look for differences. Perhaps the signal is dropping out intermittently, but the dropout happens too quickly to be captured by the freeze frame data.

I closely inspected the connectors for all three MAP sensors, and the wires leading up to the sensors, and I didn't notice anything out of the ordinary. No frayed wires, no loose connections to the crimped contacts. However, I did notice that the white rubber seal on the connector for MAP 2 looks a little beat up & torn, and it kind of jams up when plugging the connector into the sensor. Perhaps moisture is getting in there? The humidity in NH has been very very high in the past week or two. Typically 80% or more. Replacing the connector body wouldn't be too hard, and I have the tools to remove the socket contacts from the body.

In other news, the car has been running good and the code hasn't resurfaced in the last two days of commuting. I've done a healthy mix of highway, back-road, and stop-and-go driving. I've driven it quite conservatively for the most part, but also have done some spirited pulls here and there. Both with A/C on an off, in comfort & dynamic, just trying to create different load & rpm situations resulting in large swings of boost/vacuum.

Maybe I'll post some more data later this evening to match the sample data you provided. Thanks for the help and the insight!

[ValidatedS4]

Subbed. Keep us posted. I’m having similar issues and symptoms with my S4 and similarly in NH as well lol. I haven’t had time to inspect the wiring for my MAP sensors. Was thinking about replacing them as next steps.


Sent from my iPhone using Audizine

[Smac770]

PUT = Pressure Upstream Throttle, so PDT is likely Pressure Downstream Throttle?
SP = Set Point, logically synonymous with SPecified

http://nefariousmotorsports.com/foru...=14999.0title=
first link. It's a bedtime read, only 13000 pages.

ENVD = ENVronmental Data, but they are 8-bit values rather than 16-bit values of the live measured data


MAP_1_MES, Measured intake manifold pressure 1
MAP_1_MES_BAS, Measured intake manifold pressure 1 - raw value

PDT_MES, Measured pressure downstream throttle

But we don't find a PDT_MES. This is the major problem with Ross-Tech throwing their labels on there, removing the proper technical designations for the variables. Now when the Continental documentation refers to PDT_MES, we have to guess which IDE or ENG value is that.


At least the necessary documentation is there. And it's in English! The Bosch document for the CAEB I have, it's all in German. Either way, that'll take some time to digest.

[Smac770]

So section 47.42:

For systems equipped with four air pressure sensors (PDT-, AMP-, 2 MAP-sensors) the plausibility diagnosis is done by comparing the measured pressures at stopped engine, when there is ambient pressure everywhere, also at the throttle and in the intake manifold. If three sensors show the same pressure and a fourth differs significantly, the fourth sensor is implausible.

For systems equipped with a PDT sensor and 2 MAP sensors the plausibility diagnosis is done by comparing the measured pressures at part load, pull, idle speed and if no AMP sensor is available at stopped engine, when the pressure downstream throttle and the intake manifold pressure should be close to each other. If two sensors show the same pressure and a third differs significantly, the third sensor is implausible.

As I mentioned, in your case, your PDT is quite different than MAP_1 and MAP_2, by 14.86 kPa. Which is more than the thresholds defined in the P012B specification for the 3.0T. I suspect the two bullet points in the P code spec is for the two scenarios in the Simos documentation. The B8 3.0T does not have an ambient pressure sensor, so the second threshold criteria would apply, not the first. And 14.86 kPa is more than 12 kPa.

Why is your supercharger inlet pressure sensor reading much lower than within spec of the supercharger outlet pressure sensor readings? No idea. You'll probably need to run logging and try and determine under what conditions the gap occurs, then speculate from there. There's also the fact that this P code is a rationality check, not an outright operational error. If you've changed the operating parameters of the physical engine, maybe that level of boost is not unexpected, but the Simos programming is set to flag it as "nope, not supposed to be that way".

I guess the P code itself points to the PDT as the concern: Turbocharger/Supercharger Inlet Pressure Sensor
Engine RPM: 2033.00 /min
Normed load value: 26.7 %


ES = Engine Stopped?
PWL = post operating phase? No idea what that means
PU = PUll = WOT?

So 47.42.2.5 is likely most applicable. But I don't know what the MAP values are for "non-charged" vs. charged. The idle values from the blockmap I sampled were around 300 mbar. Your freeze frame values were 562 mbar, so I assume that means charged, as I believe the system design is to cap at 800 mbar "boost". So 47.42.2.5.2. But that section doesn't seem to have a check of the PDT. It's like 47.42.2.5.1.2 is really where the P-code falls. But how is 562 mbar not part-load charging?

[Salvage_B8_S4]

So section 47.42:



As I mentioned, in your case, your PDT is quite different than MAP_1 and MAP_2, by 14.86 kPa. Which is more than the thresholds defined in the P012B specification for the 3.0T. I suspect the two bullet points in the P code spec is for the two scenarios in the Simos documentation. The B8 3.0T does not have an ambient pressure sensor, so the second threshold criteria would apply, not the first. And 14.86 kPa is more than 12 kPa.

Why is your supercharger inlet pressure sensor reading much lower than within spec of the supercharger outlet pressure sensor readings? No idea. You'll probably need to run logging and try and determine under what conditions the gap occurs, then speculate from there. There's also the fact that this P code is a rationality check, not an outright operational error. If you've changed the operating parameters of the physical engine, maybe that level of boost is not unexpected, but the Simos programming is set to flag it as "nope, not supposed to be that way".

I guess the P code itself points to the PDT as the concern: Turbocharger/Supercharger Inlet Pressure Sensor
Engine RPM: 2033.00 /min
Normed load value: 26.7 %


ES = Engine Stopped?
PWL = post operating phase? No idea what that means
PU = PUll = WOT?

So 47.42.2.5 is likely most applicable. But I don't know what the MAP values are for "non-charged" vs. charged. The idle values from the blockmap I sampled were around 300 mbar. Your freeze frame values were 562 mbar, so I assume that means charged, as I believe the system design is to cap at 800 mbar "boost". So 47.42.2.5.2. But that section doesn't seem to have a check of the PDT. It's like 47.42.2.5.1.2 is really where the P-code falls. But how is 562 mbar not part-load charging?

Sorry for the late response. Had a busy weekend. Thank you so much for the clarification on these parameters. Still trying to digest it all and read that Simos documentation. 13,000 pages is quite the bed time read . I'm also unsure of what the MAP values should be for charged vs uncharged. I would think that in general, pressure from PDT would be a bit lower than the post-supercharger MAP sensor measurement, because one is un-charged air, and one is charged air, but I could be wrong.

So because no AMP is available at stopped engine, the rationality check is done at part load, pull, and idle speed? In my freeze frame, I'm doing 2000 RPM @ 43 kmh (26mph), most likely cruising along at partial throttle in 3rd gear with the AC on, so part load maybe? I wish the throttle body angle was also shown in the freeze frame data...Based on the date, I know this is roughly 2 days after I replaced that PDT sensor. The car should've "learned" and adjusted to the operating parameters of the new sensors at that point. However, I was still running my aftermarket air intake filter "dry" with no oil on it. Perhaps after sitting for a bit, small dust particles and debris was still getting past the filter and fouling up the sensor slightly, causing a rough condition for the rest of that drive cycle, throwing CEL. Then, after a bit of fresh air has cleaned the sensor off, and the car is restarted, it performs the rationality check again and everything is good, car runs great, but CEL is still on because it needs to confirm it for a few more drive cycles. There has been an unusually large amount of pollen in southern NH these last few weeks. And even though my hood is closed, pollen still makes its way ALL over the engine bay.

Although I don't have any saved freeze frame data from back then, I also got this condition when I over-oiled my air intake filter at the end of May, which prompted me to clean all sensors, clean throttle body, and thoroughly wash the air filter. So perhaps any sort of foreign debris on the sensors, oily vapor particles or dirt/debris/dust, can throw off the pressure values. But 14.9 kpa is an awfully large difference, and it seems hard to believe that a bit of debris would throw off the reading by that much. This is all just wild speculation.

Unfortunately, I have not been able to recreate these conditions! I've been monitoring MAP values during startup, idle, and having a passenger watch them during driving, and we saw nothing that jumped out as unusual. Under different loading conditions, the values all seemed to track pretty well with one another. The air filter now has a proper, very thin coating of oil on it, and I've gotten no problems. It's very unfortunate that the problem has seemingly gone away, but I have no definite answer for the root cause of the problem, and I actually don't know what fixed it. Cleaning my sensors, replacing my sensors, inspecting/cleaning the electrical connectors, or re-oiling my air filter? I changed too many variables at once, and have effectively ruined the scientific approach that I should have taken for analyzing and solving the problem.

VCDS logging kind of stinks, so I'm going to use the 034 logging tool and try and capture some logs of startup, idle, normal driving, and WOT so I can try and make sense of the data and understand the relationships between the values. I'll also send my logs to 034 to see if any of their tuners/software guys see something unusual. If I have time, maybe I'll throw all the old MAP sensors back in and re-do the same logs, and we may be able to definitively say that one of the sensors was actually bad. But hopefully everything that we've discussed here will still help someone out to a certain degree, and they'll learn something along the way.

[Smac770]

VCDS logging is great, minus the 12 parameter limit; there's no excuse for that artificial limit in the 2020s. Make sure you're using Group UDS or the sample rate will severely suck. Trying to use VCDS as a substitute for Excel for parsing the log data is a bad idea. I never try to parse logs within VCDS, only in Excel. Does the 034 tool provide you different labels for the PIDs than what you're seeing in VCDS? There is that issue with the labels, now that we have a tech doc with the proper variable names.

Could well be nothing more than a transient issue related to the filter oil. The issue is flagged intermittent, and only had a fault frequency of 3. I don't have a 3.0T, so can't offer any normal values for PDT and MAP_1 and MAP_2 under various conditions. As you say, one would think the PDT value being less would be expected, at least under charging. But idling, it should be within a range of the manifold pressures. That's why the trigger point is at least 120 mbar. And why we don't see a PDT vs MAP rationality check listed under charging, only under part throttle (not charging). Yeah, what constitutes that under/over line in the sand, don't know. Haven't really gotten back to the doc since my prior post.

[Salvage_B8_S4]

Subbed. Keep us posted. I’m having similar issues and symptoms with my S4 and similarly in NH as well lol. I haven’t had time to inspect the wiring for my MAP sensors. Was thinking about replacing them as next steps.


Sent from my iPhone using Audizine

Sorry to hear you're also going through these issues. I would dare say clean/replace your air filter as a first step. And then, pull all 3 map sensors, inspect them, and clean them with CRC Mass-Air-Flow sensor cleaner. The one in the back of the supercharger kinda sucks to get too. Pull the plastic cover with the Audi logo to expose the bank of vacuum solenoids behind the supercharger. Then, unplug those 3 solenoid connectors, the 2 throttle body connectors, and the one for the MAP sensor and pull that whole clump of wires out of the way. Then, you should have access to the two T27 screws on the back of the sensor. There's decent room to back those two screws out, but make damn sure you don't drop them. With screws removed, pull gently and STRAIGHT BACK on the sensor, maybe using a screw-driver/small prybar to ease it out. There's an O-ring in there that holds it pretty tight in the hole. I've heard of people snapping off the stem of the sensor when removing it so be careful.

The 2 MAP's on the sides of the supercharger are very easy to get to and remove. Just some T25's for the plastic trim piece, and T27's for the sensors themselves.

If you do end up just replacing them, here they are.

Here are the two on the sides of the supercharger: https://www.ecstuning.com/b-bosch-pa...YaApmwEALw_wcB
Here is the one on the back of the supercharger: https://www.ecstuning.com/b-bosch-pa...3c906051f~bos/

They look similar but they are indeed different sensors. If you take the Bosch part # right off the pictures, you can order them off amazon too. Autozones and Advanced Auto and Oreillys might also have them in stock, but they'll charge a little bit more for them.

[Salvage_B8_S4]

Bump. Just got the P012B code again. Similar conditions. PDT_ENVD is lower than MAP 1/2_ENVD.