2001 Audi TT 225 hp engine, CEL, ABS, ESP lights all on and a strange sound


Hello again sages of the car talk forum. This question regards my 2001 Audi TT with the 225 hp turbo charged engine rather than a BMW. What can I say, I have a thing for aging German luxury cars.

Anyway, I’ve had three lights on for a little while now. A check engine light, the ABS light, and the Electronic Skid Protection light. I just had the code pulled for the CEL. It’s a P1136. According to AutoZone’s handy little computer it relates to a lean fuel mixture and could be a vacum leak, a bad heated O2 sensor, or a failing fuel pump.

Here’s why I’m curious about your thoughts on a Vacum leak, or maybe this is an separate issue altogether. When accelerating through town at lower speeds and shifting gears I’m noticing an interesting sound. It only occurs under load and I can not simulate the same sound when the car is sitting still. If while accelerating I rev the car up to about 3 revs and then remove my foot from the clutch and ease on the gas while changing gears I get a sucking sound. I’m going to try to record it, but I don’t know if I will be successful. The sound could best be replicated if you took an air hose and quickly pumped the trigger 5 or 6 times. Sus sus sus sus sus sus, like that. Say it out loud fairly quick and I think you’ll get the idea.

So what do you guys think? I’m heading down to work on it right now. I’ll check back in a few, but what are the odds that… wait for it… I have some sort of vacum leak around the brake booster causing the sound, and all three lights? Any chance I can kill 4 birds with one stone?

Additionally, this is my first vehicle with a turbo, so I’m willing to admit that this may simply be a case of a normal turbo sound that I don’t recognize. I do know the whistle sound. Let me know. Meanwhile I’ll be looking for vacum leaks and trying to get a recording.

If your brakes are operating normally, I tend to doubt that you have a vacuum leak in the brake booster or the hose leading to it. It is possible, of course, that there is a vacuum leak in another place.

I would also tend to rule out your fuel pump if you are not having driveability problems.

That brings us down to the other possibility that you mentioned, namely a bad O2 sensor. If I was a betting man (especially if I was able to bet $10k at a time, like Mitt Romney), I would place my bet on a bad O2 sensor.

Additionally, you should be aware that when the car’s OBD system detects a fault, it will frequently disable the Stability Control System, the Traction Control System, and possibly the ABS and the Cruise Control. Because of the interaction of the ECM with these other systems, many faults that are significant enough to turn on the CEL will also turn on those other warning lights, indicating that those systems have been disabled as a result of the fault.

Well, I don’t know 100% yet @VDCdriver, but I did find a bad hose with a vacum leak. So I’m off to the store to get a replacement. I’ll be sure to post back if it resolves the issue. I’m not sure if the brake booster was involved at all, and yes my brakes feel fine. It’s back to an ABS sensor on those if this doesn’t kill my christmas tree dash on it’s own.

A problem with the ABS should not result in the CEL being lit up.
The CEL is, after all, the Check ENGINE light!

Then again, Audis are renowned for all sorts of weird, transitory, hard-to-resolve and even harder-to-fix electronic problems. Overall, my money is still on a bad O2 sensor, but I have been wrong before.

@VDCdriver: I’m thinking more the reverse, the same problem that causes the CEL is causing the ABS/ ESP lights. In any event, I just finished replacing the hose, so I’m giving it a few minutes to sit with the battery disconnected and then I’ll be putting it through a couple start up / shut downs and taking it on a test drive back to autozone to have the codes pulled again, hopefully I won’t see at least the CEL this time and if I’m lucky I might get rid of the other two. In my Googling I have come across a couple situations in which the CEL turns on the other two lights as well. Now, if only that airbag light would turn off. I’ve heard that is damn near impossible to get rid of though.

The Check Engine Light, ABS light, and the ESP light are inter-related. The ESP system utilizes the ABS and the engine management computer to keep the vehicle under control in the event the driver crosses the parameters where control of the vehicle may be lost. For example, if you were to attempt to take a clover leaf ramp on the freeway at 80 MPH, the ESP system would start applying the ABS and reduce power to the engine via the engine management computer to bring the vehicle back under control before you even had a chance to lose control. So when all three warning lights come on all three systems have to be inspected.

It’s sorta like with early ABS. If the primary brake warning light comes on, the ABS warning light automatically comes on because the ABS won’t function if there’s a problem with the primary brake system. But if there’s only a problem with the ABS, the ABS warning light comes on but it doesn’t cause the primary brake warning light to come on.


“Now, if only that airbag light would turn off. I’ve heard that is damn near impossible to get rid of though.”

You hadn’t previously mentioned the SRS light!
Normally, this will only light up if there is a fault in the circuitry or the sensors that would cause the airbags to be non-functional. But…since this is an Audi…the usual causes are not necessarily the problem here.

I know a woman who used to own an Audi TT (vintage 2002, I think), and, from the time that it was new, the only way that she could get the windshield wipers to work was to hit a specific place on the dashboard VERY hard. How did she know that? Because the technicians at the Audi dealership advised her to do this after they ran out of other possibilities for resolving her wiper issues. So–even the “factory-trained technicians” couldn’t figure out her Audi’s electronic woes, and they told her that they had figured out this “fix” for the other TT owners who had the same problem.

As I said previously, Audis are renowned for all sorts of weird, transitory, hard-to-resolve and even harder-to-fix electronic problems. After a couple of years of worsening electronic problems, she dumped the car on someone else who professed to “love Audis”. She was very glad to be rid of the car.

THAT noise is most likely your Blow off valve…might be having issues as the OEM is designed to be quiet…tuners like to use the noisy ones…so you hear a Tsssssst between shifts…kinda sounds cool with the turbo spool sound preceeding. But yeah you have some valving in your intake/pressure side to the Throttle body…look round there for it…if not there its SOMEWHERE On the pressure side methinks.

The ABS light will go on foyou between 70-90K…JUST for kicks… You need to invest in a VAG Com to read interpret and reset your codes properly…simple OBDII handhelds don’t do much for VW/Audi products.


@Tester: It had been my hope that this would be a one fix all lights out solution. It didn’t work out that way though.

I can say that I think I’ve successfully cleared the check engine light. Now that I’ve replaced that vacum hose and it seems to be taken care of it’s down to the ABS and ESP lights. So I think I’m back to testing ABS sensors. Unfortunately, I can’t find a OBD to USB connector anywhere locally, so my Vag Com is useless, so it’s down to checking each one individually, UGH!

@VDCdriver: I did not mention the airbag light because at least in this case it isn’t pertinent. It’s been on since I purchased the car. The reason is simple, the former driver got pissed off in traffic and punched the shit out of the center of the wheel. Or he just got into a tight spot and nailed the horn really hard if you want to give him the benefit of the doubt. Whichever. In any event, that was a pre-existing problem and unless there is a number of on-off cycles to clear the other two lights they don’t seem to be connected to the CEL.

So, I guess the next thing to ask is how would one go about testing an ABS sensor once it has been removed from the car?

Ok, so it doesn’t look like testing the sensors should be all that difficult. I’ll be tackling that task tomorrow. With any luck I should get some results that will tell me if one of the sensors is out. I get to break out my multimeter!

@Blackbird: Oh yeah, I had wondered if that sound was the blow off valve, but it looks like it was the broken vac hose. It no longer makes that sound since the hose replacement.

Ya know what I would do next? Check the wheel speed sensors and the sensor tone rings for excess debris and dust. If enough debris and dust fills in between the teeth that makes up the tone rings, it can mess the signals up to the wheel speed sensors. This is especially true if the brake pads are of a semi-metallic compound.


@Tester: Semi-metallic you say? Uh Oh…

Yeah, I’m going to be testing each of them from the engine compartment tomorrow first thing. Next thing will be to investigate at the wheel if one of them comes up bad. If none come up bad maybe all wheels.

Maybe I should check fuses as well…

Please momentarily excuse my intense excitement…


My Googling has saved the day again. I found a complete Audi Factory Repair Manual section dealing with the ABS system. I have the pin outs to the control module and specified values for each component as well as step by step testing procedures straight from Audi. It has been a good night, and it’s multi-meter time tomorrow. Now where did I put that fancy set of testing leads…

LOL…welcome to a day in the life my man… Tester is correct about those rings…ARE you trying to clear the ABS light? YOU NEED A VAG COM…WHICH IS THE USB TO OBDII CONNECTOR AND SOFTWARE>>>>

That is really the only way, unless someone know enough sw writing and coding AND feels like doing it all over chat…you need the correct device…DO NOT INVENT YOUR OWN…OR DO>…if thats your goal…

What you can do if you are in a hurry is simply go to a VW/Audi forum…and say HEY GUYS…whos got a VAG COM HERE? Are you local? Give you $20 bucks to check me out reset lights…not only do you make a good friend in the proper community, you learn something in the process.

I know that my 2000 Chevy Impala will turn on the ABS and traction control warning light and disable both if the fluid in the brake reservoir gets low. So check brake fluid level first on the outside chance that low fluid could be the cause

@Blackbird: it won’t be as fast as using vag com, but I should at least be able to fix whatever part of the system is broken. Since the light has turned off breifly on occasion I’m under the impression that it may turn off if I fix the fault, but I’ll just have to see.

As for getting Vag com myself, I do have a Windows software package and all I need is the OBD to USB connector. May be an attractive investment.

@americar: I’ll be checking that as well.

For anyone checking my work, here is the plan:

Check fluid resivoir
Check fuses
Remove and controller and check pin outs from sensors

Great joy?

Well… Great joy assuming I find the rotten apple and can take a look at it at the wheel or wherever it is.

Oh yeah, I also forgot to mention that the strange sus sus sus sound I had been hearing is gone as well. It must have been a result of the vacum leak.

Off to do some testing.