Hi, my son has a 1998 Audi A4 with a manual trans. When we got it, there was black tape on the instrument panel covering many idiot lights and the fuel guage and temp guage didn't work. The idiot lights are: air bag, temp, ABS, brake, and low fuel. I put my OBII analyzer on, and only got a P116 code which is or coolant temp. Maybe that's the problem, but what about all the other problems? I doubt they are all real. The main computer has been changed by the previous owner. He said there is another computer under the steering wheel that will probably fix the problems. My question is : Does anyone know what could be causing all the guage and idiot lights problems? Please let me know!!!!!

 

That sucks that you had so many problems with the car, but some may well be ghosts. Some of them probably are very real, as they're common on these cars, but they're easy fixes. Best thing you can do is go to www.ross-tech.com and download the USB 409 version of VagCom (Audi's diagnostic software) onto your laptop. The shareware version is free and does a great job with most of the issues you'll face. Buy an OBD2-to-USB cable on eBay for $20, and you're in business.

First thing is to clear any and all codes in the car - ECU, drivetrain, etc. The ones that come back are what you have to deal with. The ones that don't are likely transient issues that happened once and never again, or that were fixed and the codes weren't cleared.

Now, I don't know of any computer under the steering wheel, and I've torn apart more than my share of A4s in repairs and modifying. Here's my take on your idiot lights:

airbag - likely a real, but intermittent fault. If you scan the airbag codes you're likely to find that it's been triggered by one of the two front seat airbags (they're built into the outer side bolsters). If the seat is put too far back, it strains the connectors and opens them for a split second, which is enough to trip the fault light. Get down in the footwell and look under the front of the seat - you'll see a large connector there, and next to it, a smaller, yellow connector - that yellow one is the airbag connector (by law, airbags must be connected with yellow connectors, and nothing else can be, so that there is no mistaking one). Using small zipties, strap the connector tightly together to hold it so it can't separate, then turn off the bag light with VagCom and you should be good to go.

coolant temp - likely a faulty coolant temp sensor (which is backed up by your stored fault code) - they're notorious on these cars and they can create a ton of issues when they die. They're about $25 and easy to change. I don't know if you have a turbo four or a V6, but either way, if you use the search feature here on the site, you'll find all you need to know about changing the sensor. It'll fix your fault code, and likely your temp gauge as well, since the one sensor is used by the ECU to gauge engine temp, and it then uses that info to drive the temp gauge electronically.

ABS - probably a bad wheel speed sensor - they can get damaged. You'll need VagCom to tell you which one it is, then you can change it. They're plugged into the hubs at each corner.

brake - could be a wear sensor on the pads, although I am pretty sure the A4 didn't get the wear sensors until the mid-99 facelift (which is known as the 99.5 model). You may have a brake light bulb either out (in either taillight or in the third brake light), or a bulb that is incorrect, even if it fits (these cars look for a particular impedance and not all bulbs have it - order bulbs from www.ecstuning.com to get the right ones).

low fuel - the fuel sending units are known to have issues, creating all kinds of random screwy readings on the gauge. On the sending unit, there is a small wire going across the face of the resistor board under the float boom. This wire frays and breaks, creating the irregular readings. It's an easy fix. Go on this forum to the DIY forum and look for the "fixing an erratic fuel gauge" procedure. If you don't find it there, look at www.audidiy.com or at www.audiworld.com (click Resources, then Tech) - it's at one of these sites. It'll walk you through it step by step. It's a very easy fix and even though the DIY says to solder it, you don't have to - I was out of solder so I just used a butt splice connector and reattached the two broken ends. No problems since.

That should get you through the issues you mentioned - if you need more feedback on them, best bet is to post in the A4 forum, B5 subforum (which covers the 96-01 A4). We have a ton of knowledgeable members there and we'll get you taken care of.

Welcome to AF

 

Wow, I never expected such a thorough response! Thank you so much because I'm used to owning Jeeps. I will check out all the suggestions you have made. I tried to replace the cts, but advance and checker and autozone all had the wrong sendors. We ordered from Car Parts Warehouse. I can't tell how much I appreciate your help. I was ready to give up and just sell the car.
THANKS AGAIN, FRANK

 

Anytime For future reference, you're best off getting your parts from the forum sponsors. On the east coast, www.germanautoparts.com in Albany, the Midwest is where ECS Tuning is, and out west is www.purems.com - many of us have dealt with them with great success. They're VW/Audi specialists which can help a lot because there are so many year-to-year changes on these cars. Your CTS for example should be the blue sensor (the early cars used a black one and the later ones use a green sensor - it does make a difference). ECS and PureMS will look up the proper part based on your VIN number to be sure you get the right parts.

When you go to investigate this stuff, if you get stuck on anything, post back up in this thread with what you are wondering. My user preferences are set up to email me anytime someone replies to a thread I've contributed to, and I get my email on the spot on my iPhone so I can get right back to you. I'll walk you through these and we'll get your car straightened out. There may be some tips and tricks I've learned doing these that I can pass along as well.

And before you go out there, go to the B5 subforum and look for the thread called "better than finding a $20 bill" - it's a listing of a bunch of little features and tricks about these cars that aren't readily apparent. There are some cool things you'll probably want to check out.

 

Also, take a minute to go to your User Control Panel (link is up above on the jump bar) and add two things. One is your location - you may find that you have other members local to you who can come by to pitch in with diagnostics and repairs, or even just to have a beer and talk cars. The second is to create a signature including the year, model, engine, and drivetrain of your car (mine is a 99 30-valve V6, with quattro awd and a manual transmission, and I abbreviated it as you see in the sig). That'll help a lot with having others pitch in when you have a question since they'll know at a glance what type of car and configuration you have, and it'll save you having to list it every time.

 

Hey, Thanks for all your help. Let me tell you what is fixed.
1 Airbag light- the car has no side airbags, hence no yellow connector under the seat.
2 Blinking brake light- all bulbs for brake lights top and bottom are good and the same brand from Hungary. So, the brake light is still on.
3 ABS light- went around the car and found a repaired wire for the right rear wheel abs sensor. I found twisted wires, and soldered them, but light is still on.
4 Temp guage- replaced temp sensor. Guage now works. Cool!
5 Fuel guage reads empty- Tomorrow will check sending unit in tank.
I was really surprised that I'm getting used to the German way of car design. It's getting easier to work on this A4.

 

Hey, thanks for the info about how to fix the car. Here is a report.
1 airbag light- the car has no side airbags, hence no yellow connector under the seat.
2 blinking brake light- all bulbs were good and made in Hungary. Even the top set of lights in the back window were good.
3 ABS light- found a repaired wire near a sensor and found twisted wires only. I soldered them, but still ABS light is on. Oh, well.
4 Temp guage not working- replaced coolant temp sensor, and now guage works.
5 Fuel guage is dead- Will look for sensor in tank tomorrow. Hope it works.
If you have any more ideas, please let me know!

 

OK, in order:

1. If there are no side bags, then it must be one of the front bags that's causing the fault. You'll need VagCom to scan the computer and see which one is causing the failure. Download it and get the interface cable on eBay and then we can figure out what to do from there.

2. It's possible that the blinking light is referring to a problem with the ABS controller (which should set a fault code, but may not necessarily) or you could be low on fluid - I'd check out both of those.

3. Replacement is the best idea for this. The ABS sensor is nothing more than an inductive pickup and just twisting the two ends together may not allow the ECU to see what it should. Also, on my car when I replaced the ABS sensor the light extinguished itself, but it's possible that you may have to turn it off manually via VagCom. Or, that may have only been part of the problem. If it is the ABS module, it'll trip the ABS light as well as the brake warning in #2.

4. Good fix - that's usually the problem and when the CTS fails, you won't believe some of the screwy stuff that happens as a result. On top of that, the ECU reads the CTS, and then drives the gauge accordingly, unlike some Japanese cars that have one sensor for the ECU and a second one for the gauge. With our setup, if it was reading low temperature, the computer thinks the car is cold and will fuel it accordingly. In that case, you've been running rich and losing fuel economy and some power, so that should be restored now as a bonus.

5. The sensor is easy to pull - just remove the access cover in the trunk, slide the feed and return hoses off, undo the top electrical connector, then get the locking ring off with a hammer and screwdriver. On the bottom side of the cover that you'll remove, there are two connectors. The black one goes to the sending unit. Follow it down and you'll find it. It has a rectangular vertical shaft that snaps into a receiver on the pump. Just push the "unlock" tab and slide it up and out. If the wire is broken, you'll see it and can repair it. If it's not, use electrical contact cleaner to clean the contact plate and the black connector, and then put it back in. Chances are it'll be a fix.

Sorry it took so long to get back to you on this - been a busy week or two If you need a faster reply, you can always send a Private Message to me by clicking my screenname and selecting that option. I get email notification via my phone instantly, so I'll be able to get back to you faster.