A6 transmission & engine codes
07-19-2006, 11:26 AM
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A6 transmission & engine codes
The mystery continues with eratic downshifting on my A6. Neither my Indie, the Audi dealer nor ZF Tranmissions seem to have run into the specific problem.
Electrical seems to be the guess concensus...harness, speed sensor, MAF sensor, MAP senser, TCU suggested so far.
The Audi dealer offered to replace the harness first for $550 bucks with no guarantee that would solve the problem. Then just poke away until they find it.
Anyway, ZF recommended a code scan. One person has told me codes do not remain resident after 50 engine starts. Another says, unless the gear lights are illuminated on the dash, there are no codes stored. Any of you guys familiar with code scans? Will they be there? Have never had it done.
Further ideas would be appreciated.
Tom G
Electrical seems to be the guess concensus...harness, speed sensor, MAF sensor, MAP senser, TCU suggested so far.
The Audi dealer offered to replace the harness first for $550 bucks with no guarantee that would solve the problem. Then just poke away until they find it.
Anyway, ZF recommended a code scan. One person has told me codes do not remain resident after 50 engine starts. Another says, unless the gear lights are illuminated on the dash, there are no codes stored. Any of you guys familiar with code scans? Will they be there? Have never had it done.
Further ideas would be appreciated.
Tom G
07-19-2006, 03:01 PM
#2
Some thoughts
Why didn't your stealership do a code scan on the trans?
Can the VAG-COM unit do the trans codes?
Sometimes on what appear to be complex driveability issues, especially intermittent ones, you need to diagnose your way around the problem.
In other words, if you can't find out what's causing it, try to find out what's not causing it. Work from the simple to the more complex reason.
If you want to see if the harness is at fault, tie a length of string around the harness, run the string in through the window and go for a drive. Drive at a steady speed and have a helper start pulling on the string. If nothing happens, move the place where the string is tied around and go for another drive. If you get no response, you can probably rule out the harness because while driving normally, the harness isn't going to be moving as much as you just moved it with the string.
I don't know anything about these transmissions, but alot of modern transmissions have electronics living down in the pan and valve body. These connectors live in 200*F trans oil and can fail due to vibration, heat, solder going bad, being poorly manufactured, etc. If this is the case with this ZF tranny, then that's another item you could check by pulling the pan and inspecting with a very powerful magnifier and flashlight.
I'm just thinking out loud here, but that's sort of how I approach stuff. That, and sometimes you have to let the problem get worse, so it's easier to diagnose......like I inadvertently did recently on my 3rd brake light inop threads.
Can the VAG-COM unit do the trans codes?
Sometimes on what appear to be complex driveability issues, especially intermittent ones, you need to diagnose your way around the problem.
In other words, if you can't find out what's causing it, try to find out what's not causing it. Work from the simple to the more complex reason.
If you want to see if the harness is at fault, tie a length of string around the harness, run the string in through the window and go for a drive. Drive at a steady speed and have a helper start pulling on the string. If nothing happens, move the place where the string is tied around and go for another drive. If you get no response, you can probably rule out the harness because while driving normally, the harness isn't going to be moving as much as you just moved it with the string.
I don't know anything about these transmissions, but alot of modern transmissions have electronics living down in the pan and valve body. These connectors live in 200*F trans oil and can fail due to vibration, heat, solder going bad, being poorly manufactured, etc. If this is the case with this ZF tranny, then that's another item you could check by pulling the pan and inspecting with a very powerful magnifier and flashlight.
I'm just thinking out loud here, but that's sort of how I approach stuff. That, and sometimes you have to let the problem get worse, so it's easier to diagnose......like I inadvertently did recently on my 3rd brake light inop threads.
07-19-2006, 03:49 PM
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Re: Some thoughts
Hey Austin, appreciate the thoughts. I have no problem with the stealership pulling codes, if they exist. The ZF guy suggested that as a first step and it makes sense. He was extremely helpful and they should since they build the transmissions for Audi.
In my research I am learning there are a lot of electronics, sensors and logic chips involved with making the A6 shift. The dealer tech told of a fault that could occur in the brake light sensor that would send a false signal to the transmission.
I will try the harness to string idea if I can find out out where the harness is.
Thx, Tom G
In my research I am learning there are a lot of electronics, sensors and logic chips involved with making the A6 shift. The dealer tech told of a fault that could occur in the brake light sensor that would send a false signal to the transmission.
I will try the harness to string idea if I can find out out where the harness is.
Thx, Tom G
07-19-2006, 04:27 PM
#4
Go get some metal ramps
Put the transmission into 1st and carefully drive up onto them. Set the brake, engage park, and then take a trip below decks. You'll see where the connectors are on the transmission.
I've actually seen connectors for the trans (on a different make/model of car) get full of oil from an engine oil leak and this caused all sorts of bad shifting and driveability...to the point that one dealer replaced the trans, to no avail. The solution wound up being: spray out the connector with carb cleaner, blow dry with compressed air, drive car....fixed.
So don't get too wrapped around the axle of logic circuits, computer failures and bad muffler bearings. I could be something very simple.
See if you can't nail down more about "when it does it" and corollate that to something tangible. At least that might get you started in a direction.
I've actually seen connectors for the trans (on a different make/model of car) get full of oil from an engine oil leak and this caused all sorts of bad shifting and driveability...to the point that one dealer replaced the trans, to no avail. The solution wound up being: spray out the connector with carb cleaner, blow dry with compressed air, drive car....fixed.
So don't get too wrapped around the axle of logic circuits, computer failures and bad muffler bearings. I could be something very simple.
See if you can't nail down more about "when it does it" and corollate that to something tangible. At least that might get you started in a direction.
07-20-2006, 02:58 AM
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On top of all that good advice...
There was an Audi tech artical explaning a problem with the harness and how to check it. If the dealer gets his thumb out of his a$$ he'll find it.
Basically it tells you to check the points where the harness is attached to the chassis and look for damage due to it being secured too tight.
Also to do continuity tests between the TCU connector and the connector at the transmission with an ohm meter.
Basically it tells you to check the points where the harness is attached to the chassis and look for damage due to it being secured too tight.
Also to do continuity tests between the TCU connector and the connector at the transmission with an ohm meter.
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