This is from an Audi A6 2001 Quattro 2.7 Turbo.

The automatic transmission went into limp home mode last week, and won't come out. I dropped the pan, changed the filter and fluid, which was dark like lightly used engine oil - mid/dark brown. There was a little sludge, but nothing too terrible and no obvious metal particles. Didn't make any difference though - it's still stuck in limp home mode, even after clearing all the codes.

I’m getting the following codes, which come back as soon as I move after clearing them: -
• 17100 Transmission Input Speed Sensor (G182): Implausible Signal P0716
• 18238 Pressure Contr.Solenoid 4 Short to B+ P1830
• 18237 Pressure Contr.Solenoid 4 Open/Short to Ground P1829
I’ve also checked resistances at the case connector and am getting –
• Pins 8,12 - 30 Ohm (Solenoid 1)
• Pins 9,12 – 30 Ohm (Solenoid 2)
• Pins 4,12 – 30 Ohm (Solenoid 3)
• Pins 2,12 – 6.5 Ohm (Pressure Control Valve 1)
• Pins 3,12 – 6 Ohm (Pressure Control Valve 2)
• Pins 7,12 – 5.8 Ohm (Pressure Control Valve 3)
• Pins 11,12 – 5.8 Ohm (Pressure Control Valve 4)
• Pins 13,14 – 2500 Ohm (Temp - it was Cold)
• Pins 1,10 – 1100 Ohm (Output speed sensor - MUCH too high)
• Pins 5,6 – Open circuit (Turbine Speed sensor - Oops!)

This leads me to think that some or all of the following may be issues: -
1) Faulty Turbine Speed Sensor
2) Faulty Output Speed Sensor
3) Faulty Solenoid 4
4) Faulty wiring loom.

I'm thinking I may as well just replace all four of the above - what do you think????

 

What does "Replace all 4 of the above" mean?

Where did you get those codes? I don't have a VAG so don't know if those can be brought up on a regular code reader.

I never went into "limp mode". I simply lost 4th gear altogether, and the Audi dealer checked my car and said just drive it in 3rd. You won't break anything.

I still think it MAY be electronic, but I am not an Audi dealer who would prefer to sell me a tranny rebuild.

3 speeds makes me get about 3 to 4 MPG less mileage, but it runs better than it did before 4th went out altogether. 2-3, 3-4 shift was shitty before. 2-3 is relatively smooth, power is good, of course, not going from 4-3 on kickdown.

Cheers,

George

 

Check the harness too... I went through hell once replacing a solenoid pack only to have no change.. finally traced it down to a break in the harness.. in a very, very hard place to find, see, and work on..

 

Can anyone confirm that the correct resistance value for a G182 (Turbine Speed Sensor) from a 2001 A6 2.7T should be 230 - 300 Ohms please? Also, any suggestions as to where to get one quickly and cheaply?



So the saga continues. I thought I'd found a really good company who could refurbish my valve pack and all the sensors... Gave them all the info above (actually a cut and paste of my post). Sent them the valve pack as well as the OSS and TSS sensors, and instructions to test and replace everything that was out of spec. Eventually got everything back (although they seemed to "forget" about it, and only send the reconditioned parts back after I rang them several times).

Like a dummy, I didn't check the specs of the components (resistances) until I'd got everything back together and was just about to fill with ATF... good job I did though - the TSS is still reading 14 kOhm instead of 230 to 300 Ohm. Actually, my digital meter shows Open Circuit, my analog one gives the 14kOhm. This was measured with the TSS off the vehicle. Obviously the TSS is faulty. I *suspect* they didn't replace it and probably didn't even test it.

I'm not going to mention the company name *yet* - I'll see what they say when I talk to them on Monday first!!!!

 

It looks like the company I used actually knows it's stuff a lot better than all the other sources I found for information!

I got another TSS, and that one read 13kOhm, so apparently everything I've found on the internet (and in AllData) could be wrong, and 13~14kOhm for the TSS is correct. I rebuilt the transmission back up again (getting good at it - I can go from valve body out to transmission filled in about 90 minutes now!)

I *still* had 18238 and/or 18237 coming up and the transmission going into limp mode. Thinking it might clear if I drove the car a bit, to give the ATF time to get into all the nooks and crannies, TCU time to think etc (I was getting desperate!) I took the car for a gentle drive. Sure enough, after about ten minutes, all the faults cleared! Woo Hoo!

The following morning, I took the car into work. Same thing - faults when I started off, which clear after about 10 minutes. Perhaps it's temperature related? When I drove back home, the fault didn't clear :-( Instead, the second timede I stopped the car to read codes and turn/off on the ignition to see if the transmission is going to stop sulking, the battery was dead. Faint whir from the starter motor, but that's about it. Darling wifey came out with jumper cables, and we jump started the car from her ever so boring but ever so reliable Honda. Car starts fine, but ... what's this? ... the transmission fault clears. Hmmm...

So I put the car on a battery charger overnight, and this morning, from cold, everything is good - no transmission fault! It looks like the latest transmission problems were being caused (or at least triggered) by low voltage. The earlier problems where definitely mechanical in origin though - the ATF and valve body were in very bad condition, and I'd had the car on a batter charger whilst I was working on it.

I'm not certain about the current (deliberate pun) problem being voltage related yet, and I've got another N218 on it's way, but it's looking promising...

Anyway, after that short story, a couple of questions..
1) Has anyone ever had anything like that before?
2) Measured from the battery with a voltmeter, I see about 12.3v engine off, 13v engine on. Using VAGCOM and looking at the reported voltage from the TCU, it gives me 11.97v engine off, 13.31v engine on. Do these seem reasonable - they feel a little low to me.
3) Assuming I've got a current drain when the car is off, any suggestions on the best methodology to track down the culprit.


I notice there seem to have been a lot of transmission related posts recently - you might want to put your car on a charger overnight and see if it helps!

 

Those are slightly low.. should be 12-12.5v OFF, 14-14.5v Running.

 

Hi Grahamwatson,

After reading you post and hearing of the low voltage issue your experiencing, I thought to ask if you have ever had your battery and/or alternator tested to ensure that your ECU's are getting the proper power or voltage needed. Its odd to hear that you are constantly having to jump start the car. I thought maybe the erratic error codes are merely caused by insufficient electrical power.

 

Both alternator and battery were tested at Schucks - the battery in particular had a deep cycle test which took over an hour off the car. I'm suspecting either a bad connection or something sucking down the juice when the car is off... I'm sure I'll work it out this weekend. :-)

 

You may get a ZF manual from www.atsg.com

 

HI i realise this is an old subject but might help someone! I have had similar problems that drove me mad with other VAG vehicles until i figured out running a earth lead from the chassis to the transmission has "fixed" many issues with various VAG vehicles, who knew!