PRND432 all lit up part 2
01-03-2004, 12:44 AM
#25
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an explanation
emergency mode can be triggered by a lot of things - not just by a solenoid failure. there are 2 types of emergency mode:
1) mechanical ie the tcm is operatonal, and
2) electrical ie the tcm is non-operational.
when in emergency running mode (erm)
1) the tranny shifts mechanically
2) no tcc locakup is possible
3) no solenoid valves are used
4) full hydralic prssure is maintained
some events which fit your description are:
1) the failure of either the input or output rpm sensor will trigger emergency mode, but will have no major effect on transmission operation as it is mainly used to smooth the operation of the gearshifts.
2) failure of the link to the abs/asr module will have the same effect, and is used for the same outcome.
it is true that a solenoid failure will result in the erm condition, but not with the symptoms that you describe.
there are actually only 3 solenoids, and their function is to interface the electronics (the tcm) to the hydraulics (ie the clutches or brakes). they operate either on or off - no inbetween.
one solenoid is only used for neutral (n90) - the others are used in multiple gear streams.
with your symptoms, i am puzzled by the assertion that a bad solenoid is the cause, as this would mean that you would have significant loss of drive.
keep us posted, i'd love to know the error codes...
1) mechanical ie the tcm is operatonal, and
2) electrical ie the tcm is non-operational.
when in emergency running mode (erm)
1) the tranny shifts mechanically
2) no tcc locakup is possible
3) no solenoid valves are used
4) full hydralic prssure is maintained
some events which fit your description are:
1) the failure of either the input or output rpm sensor will trigger emergency mode, but will have no major effect on transmission operation as it is mainly used to smooth the operation of the gearshifts.
2) failure of the link to the abs/asr module will have the same effect, and is used for the same outcome.
it is true that a solenoid failure will result in the erm condition, but not with the symptoms that you describe.
there are actually only 3 solenoids, and their function is to interface the electronics (the tcm) to the hydraulics (ie the clutches or brakes). they operate either on or off - no inbetween.
one solenoid is only used for neutral (n90) - the others are used in multiple gear streams.
with your symptoms, i am puzzled by the assertion that a bad solenoid is the cause, as this would mean that you would have significant loss of drive.
keep us posted, i'd love to know the error codes...
01-03-2004, 08:32 AM
#27
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Dave, questions, your points reinforce one of my suspicions.
I have noteed the following. Apples to apples, this is noted post warm-up:
1. The annoying, inadvertant torque reduction that exists in second gear with the A6 4.2 is less prevalent in wet weather or snow. If it occurs, it occurs at a higher RPM.
2. The tranny shifts quicker and more aggressive in wet weather or snow. In fact, it shifts exactly the way I want it to. I found this interesting, if Bosch/Audi were truly concerned about safety in bad weather I would have expected them to engineer the opposite.
Given that there is always some level of tire slippage, I suspect that 1 and 2 are a result of the TCM reading of variance in the input and output reading. Stated another way, I believe my second gear torque reduction is triggered consistently on dry pavement because I am loading up high torque at low RPM and there is internal slippage.
In addition, I believe my subjective assessment that the S8 has "superior software coding" is a result of the 3.73 gears freeing up the system.
My questions, to get your thoughts on the above. I'm intentionally being general:
1. If one wishes to pay their money and takes their chances (not saying who that may be), the following can be tested to confirm my suspicions:
"... the failure of either the input or output rpm sensor will trigger emergency mode, but will have no major effect on transmission operation as it is mainly used to smooth the operation of the gearshifts."
2. In general, do you believe I am chasing the subjective on what I have noted?
3. Do you have reference in any of your ZF info on the Porsche or AMG ZF codings, and the Audi 4HP24? I'm looking to find a link to someone that has actually pulled and provided the software coding.
1. The annoying, inadvertant torque reduction that exists in second gear with the A6 4.2 is less prevalent in wet weather or snow. If it occurs, it occurs at a higher RPM.
2. The tranny shifts quicker and more aggressive in wet weather or snow. In fact, it shifts exactly the way I want it to. I found this interesting, if Bosch/Audi were truly concerned about safety in bad weather I would have expected them to engineer the opposite.
Given that there is always some level of tire slippage, I suspect that 1 and 2 are a result of the TCM reading of variance in the input and output reading. Stated another way, I believe my second gear torque reduction is triggered consistently on dry pavement because I am loading up high torque at low RPM and there is internal slippage.
In addition, I believe my subjective assessment that the S8 has "superior software coding" is a result of the 3.73 gears freeing up the system.
My questions, to get your thoughts on the above. I'm intentionally being general:
1. If one wishes to pay their money and takes their chances (not saying who that may be), the following can be tested to confirm my suspicions:
"... the failure of either the input or output rpm sensor will trigger emergency mode, but will have no major effect on transmission operation as it is mainly used to smooth the operation of the gearshifts."
2. In general, do you believe I am chasing the subjective on what I have noted?
3. Do you have reference in any of your ZF info on the Porsche or AMG ZF codings, and the Audi 4HP24? I'm looking to find a link to someone that has actually pulled and provided the software coding.
01-03-2004, 08:36 AM
#28
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And some informal stuff ...
I had a chance to check out the "Holden GTO" at the Pontiac dealership yesterday. I am very impressed with the ANZ execution on that vehicle, especially at the price point.
01-03-2004, 08:52 AM
#29
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Got the fault code
Dave
The fault code that the dealer has given me is
18238 p1830 035 pressure control valve-4-for auto.transmission-n218-short circuit to b+
But I think you might be onto something with the ABS, Dave. When I put it in for the service, I asked to garage to look at the ABS/traction control sensor, as the warning light for both had been popping on and off for the first 10-20 of every drive for about three weeks. Quite odd, as when the sensor has gone before, the lights come on and stay on. This time they were on for 15-20 secs, then off, until they eventually stayed off.
The dealer on that occasion allocated a fault to the ABS sensor and loom, and replaced them. Three days later up pops this problem. The only other non-standard thing done on the service was replacing the air mass meter.
I gave it a relatively hard run up & down some hills today after reading your post. Couldn't notice any extra roughness in the upshifts, even when driving hard at the top end of the rev counter.
Interested to see if you've got any further thoughts.
Cheers
Greg
The fault code that the dealer has given me is
18238 p1830 035 pressure control valve-4-for auto.transmission-n218-short circuit to b+
But I think you might be onto something with the ABS, Dave. When I put it in for the service, I asked to garage to look at the ABS/traction control sensor, as the warning light for both had been popping on and off for the first 10-20 of every drive for about three weeks. Quite odd, as when the sensor has gone before, the lights come on and stay on. This time they were on for 15-20 secs, then off, until they eventually stayed off.
The dealer on that occasion allocated a fault to the ABS sensor and loom, and replaced them. Three days later up pops this problem. The only other non-standard thing done on the service was replacing the air mass meter.
I gave it a relatively hard run up & down some hills today after reading your post. Couldn't notice any extra roughness in the upshifts, even when driving hard at the top end of the rev counter.
Interested to see if you've got any further thoughts.
Cheers
Greg
01-03-2004, 11:05 AM
#30
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ok, some more thoughts
a pressure control valve is different animal to a solenoid (although in the same family tree). as the name suggests the pcv's are used to control the hydraulic pressure to the clutches & brakes. they take a current from the tcm (actually as a duty cycle) as so, unlike a solenoid, the pcv can be anywhere between open and closed.
n218 is used for the tcc lockup, as well as during the engangement of gears 2 to 5.
display group 7/2 will display the current (amps) going to n218 - and should be anywhere between 0 to 2amps. you will need to monitor this with the vehicle on the move.
the code (short to positive - too much current) has been logged and so should be investigated. nonetheless, the fact that you state that work has been done on the abs make electrical connectors a useful 1st step in diagnosis - anything to avoid cracking the tranny as this will be expensive. actually replacing n218 isn't hard to do as it simply screws into the valve body, and so can be done in situ.
keep us posted.
n218 is used for the tcc lockup, as well as during the engangement of gears 2 to 5.
display group 7/2 will display the current (amps) going to n218 - and should be anywhere between 0 to 2amps. you will need to monitor this with the vehicle on the move.
the code (short to positive - too much current) has been logged and so should be investigated. nonetheless, the fact that you state that work has been done on the abs make electrical connectors a useful 1st step in diagnosis - anything to avoid cracking the tranny as this will be expensive. actually replacing n218 isn't hard to do as it simply screws into the valve body, and so can be done in situ.
keep us posted.