Yet more oddities with battery/power on 2004 Cayenne - please someone help!
08-27-2018, 12:14 PM
#16
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And the importance of having the correct tools comes to the fore here. You've already spent a small fortune on mechanics and new batteries - lets spend a bit on tools so we can help you track down what is actually wrong rather than throwing parts at it.
The triple-square drivers aren't expensive. Here is an Amazon link to the ones most of us use: http://a.co/d/fSDl4cC - since the Cayenne uses the bolts in numerous spots it's worth having a set, and if you have Amazon prime you can have them in your hands in 2 days.
For a multi/voltmeter - the $3.99 ones that Harbor Freight sometimes gives away aren't awful - at least if you don't bang them around a lot, and they're reasonably accurate.
What people are pointing to here - if there is a bad connection on the ground from the battery to the chassis - everything on the vehicle will receive a reduced voltage, even if the battery is fully charged. Starting the truck using the jump start terminals under the hood might bypass this bad connection allowing the vehicle to start.
One place I'd look - the front of the driver's seat pedestal (that the seat sits on and the battery lives in) - the front of it can be simply pulled off. It looks like a continuous base - but the front of it is carpet covered plastic that snaps off quite easily. Reach up under the seat, find the top edge of it and give it a tug toward the pedals. Then look for the little hatch in the carpeting near the seat pedestal. This is where the battery makes it's ground to the chassis. You'll find a big brown wire with an eye connector on it that is bolted to the chassis floor with a stud and acorn nut. Remove the nut - clean the eye lug and the surface that it contacts on the floor, then replace them and tighten (don't overdo it - you could snap the stud off.)
In order to do what v10rick suggests - you have to gain access to the battery compartment. This requires unbolting and tilting the seat back. Take a look in the DIY section, I seem to recall a DIY on replacing the battery that will help you along. You will need the triple-square driver.
Once the battery is exposed do the following:
1. Measure the voltage across the battery terminals
2. Measure the voltage across the jump start terminals under the hood
3. Measure the voltage between the positive jump start terminal and the positive terminal on the battery (you'll probably need a second person to hold one of the meter probes.)
4. Measure the voltage between the negative jump start terminal and the negative terminal on the battery
Let us know the results of these measurements.
The triple-square drivers aren't expensive. Here is an Amazon link to the ones most of us use: http://a.co/d/fSDl4cC - since the Cayenne uses the bolts in numerous spots it's worth having a set, and if you have Amazon prime you can have them in your hands in 2 days.
For a multi/voltmeter - the $3.99 ones that Harbor Freight sometimes gives away aren't awful - at least if you don't bang them around a lot, and they're reasonably accurate.
What people are pointing to here - if there is a bad connection on the ground from the battery to the chassis - everything on the vehicle will receive a reduced voltage, even if the battery is fully charged. Starting the truck using the jump start terminals under the hood might bypass this bad connection allowing the vehicle to start.
One place I'd look - the front of the driver's seat pedestal (that the seat sits on and the battery lives in) - the front of it can be simply pulled off. It looks like a continuous base - but the front of it is carpet covered plastic that snaps off quite easily. Reach up under the seat, find the top edge of it and give it a tug toward the pedals. Then look for the little hatch in the carpeting near the seat pedestal. This is where the battery makes it's ground to the chassis. You'll find a big brown wire with an eye connector on it that is bolted to the chassis floor with a stud and acorn nut. Remove the nut - clean the eye lug and the surface that it contacts on the floor, then replace them and tighten (don't overdo it - you could snap the stud off.)
In order to do what v10rick suggests - you have to gain access to the battery compartment. This requires unbolting and tilting the seat back. Take a look in the DIY section, I seem to recall a DIY on replacing the battery that will help you along. You will need the triple-square driver.
Once the battery is exposed do the following:
1. Measure the voltage across the battery terminals
2. Measure the voltage across the jump start terminals under the hood
3. Measure the voltage between the positive jump start terminal and the positive terminal on the battery (you'll probably need a second person to hold one of the meter probes.)
4. Measure the voltage between the negative jump start terminal and the negative terminal on the battery
Let us know the results of these measurements.
08-27-2018, 12:25 PM
#17
If you have the PCM removed and the fuse removed and there i still a measurable amperage draw on the vehicle when it's asleep with all doors closed, then the PCM is not your problem or there is another issue as well. The PCM is a common issue that causes a draw. Sometimes they get really hot when they fail, can be a good indicator. I would continue with the test I described if it were me. What fault codes do you have? What is the battery state of health. Again, if this were me working in the dealership this is what I would do: Check the fault memory, perform a battery, starter, alternator test (at the battery posts)(assuming all is good), test for parasitic draw, isolate the effected circuit, find the draw. Some other common checks would be: checking if the driver's floor carpet is wet/damp (the main body harness runs along the floor near the door there are 2 small splices and 1 big one when the cowl drains clog water leaks onto the carpet and corrodes these splices, this is fairly common and causes all sorts of weird issues.) I wouldn't worry to much what your battery voltage is right now, because you should have a battery maintainer on the vehicle while performing electrical tests when applicable. Also, you may check the wiring where the after market components were installed. Verify the wiring is sound, there could be a bad splice/repair/loose contact. You may also check the actual values of the doors and see if the vehicle is seeing the doors closed when they are, if not the vehicle will not go to sleep when it should and may cause a draw.
If you are able to do one thing, pull the fault codes and tell us what you have if any.
Hope this helps, let me know.
If you are able to do one thing, pull the fault codes and tell us what you have if any.
Hope this helps, let me know.
Last edited by Ptech; 08-27-2018 at 01:14 PM.
08-27-2018, 12:34 PM
#18
Nordschleife Master
And the importance of having the correct tools comes to the fore here. You've already spent a small fortune on mechanics and new batteries - lets spend a bit on tools so we can help you track down what is actually wrong rather than throwing parts at it.
The triple-square drivers aren't expensive. Here is an Amazon link to the ones most of us use: http://a.co/d/fSDl4cC - since the Cayenne uses the bolts in numerous spots it's worth having a set, and if you have Amazon prime you can have them in your hands in 2 days.
For a multi/voltmeter - the $3.99 ones that Harbor Freight sometimes gives away aren't awful - at least if you don't bang them around a lot, and they're reasonably accurate.
What people are pointing to here - if there is a bad connection on the ground from the battery to the chassis - everything on the vehicle will receive a reduced voltage, even if the battery is fully charged. Starting the truck using the jump start terminals under the hood might bypass this bad connection allowing the vehicle to start.
One place I'd look - the front of the driver's seat pedestal (that the seat sits on and the battery lives in) - the front of it can be simply pulled off. It looks like a continuous base - but the front of it is carpet covered plastic that snaps off quite easily. Reach up under the seat, find the top edge of it and give it a tug toward the pedals. Then look for the little hatch in the carpeting near the seat pedestal. This is where the battery makes it's ground to the chassis. You'll find a big brown wire with an eye connector on it that is bolted to the chassis floor with a stud and acorn nut. Remove the nut - clean the eye lug and the surface that it contacts on the floor, then replace them and tighten (don't overdo it - you could snap the stud off.)
In order to do what v10rick suggests - you have to gain access to the battery compartment. This requires unbolting and tilting the seat back. Take a look in the DIY section, I seem to recall a DIY on replacing the battery that will help you along. You will need the triple-square driver.
Once the battery is exposed do the following:
1. Measure the voltage across the battery terminals
2. Measure the voltage across the jump start terminals under the hood
3. Measure the voltage between the positive jump start terminal and the positive terminal on the battery (you'll probably need a second person to hold one of the meter probes.)
4. Measure the voltage between the negative jump start terminal and the negative terminal on the battery
Let us know the results of these measurements.
The triple-square drivers aren't expensive. Here is an Amazon link to the ones most of us use: http://a.co/d/fSDl4cC - since the Cayenne uses the bolts in numerous spots it's worth having a set, and if you have Amazon prime you can have them in your hands in 2 days.
For a multi/voltmeter - the $3.99 ones that Harbor Freight sometimes gives away aren't awful - at least if you don't bang them around a lot, and they're reasonably accurate.
What people are pointing to here - if there is a bad connection on the ground from the battery to the chassis - everything on the vehicle will receive a reduced voltage, even if the battery is fully charged. Starting the truck using the jump start terminals under the hood might bypass this bad connection allowing the vehicle to start.
One place I'd look - the front of the driver's seat pedestal (that the seat sits on and the battery lives in) - the front of it can be simply pulled off. It looks like a continuous base - but the front of it is carpet covered plastic that snaps off quite easily. Reach up under the seat, find the top edge of it and give it a tug toward the pedals. Then look for the little hatch in the carpeting near the seat pedestal. This is where the battery makes it's ground to the chassis. You'll find a big brown wire with an eye connector on it that is bolted to the chassis floor with a stud and acorn nut. Remove the nut - clean the eye lug and the surface that it contacts on the floor, then replace them and tighten (don't overdo it - you could snap the stud off.)
In order to do what v10rick suggests - you have to gain access to the battery compartment. This requires unbolting and tilting the seat back. Take a look in the DIY section, I seem to recall a DIY on replacing the battery that will help you along. You will need the triple-square driver.
Once the battery is exposed do the following:
1. Measure the voltage across the battery terminals
2. Measure the voltage across the jump start terminals under the hood
3. Measure the voltage between the positive jump start terminal and the positive terminal on the battery (you'll probably need a second person to hold one of the meter probes.)
4. Measure the voltage between the negative jump start terminal and the negative terminal on the battery
Let us know the results of these measurements.
A halfway decent set of triple squares is essential to working on one of these.
But tests 3 & 4 won't show anything. I hope you mean positive jump terminal & negative on battery, and pos on battery and neg under hood.
One more test that is absolutely imperative is to 'load test' it.
What does the battery (measured AT the battery) show when trying to crank it?
What do the jump posts show when trying to crank it?
As was noted, the fact that it will jump start from a totally dead battery, then start just fine a minute or two later is a big clue.
Knowing both battery voltage and 'system' voltage under those two situations will tell you a lot.
I'm going to guess that the ground connection between the battery and the chassis is marginal.
I will guess that the battery voltage is good, and doesn't drop when it's "dead".
This is a widely known problem in the 928 and exhibits the exact same symptoms.
08-27-2018, 01:41 PM
#19
Burning Brakes
If you can have a sub and battery, or a sub and spare, why can't you have all three since the battery fits under the sub to begin with? Did Porsche use a smaller sub when equipped with a spare leaving no room for the battery? I'm looking to add a spare to my Cayenne with sub but no 2nd battery and would hate to find out that I'd also need a smaller sub.
OP...
I have had vehicles with large alternators give enough of a surface charge to start the vehicle again after only a few minutes of run time.
Next time it acts up and you have to jump it, let it run a few minutes. Turn it off and start it again. If it starts, shut it down and turn on all the headlights for about 10 minutes and try restarting. If it starts up again, my guess would be an intermittent ground. In front of the driver's seat is a square patch of carpet you can pull up. Under that is the nut that secures your main ground cable. Make sure it's tight. From there, you'll need to lift the seat to check everything else under there...there's far more than just a battery under the seat. Testing voltage under the hood and jump starting from there is bypassing any weak grounds or positive cable connections to your battery.
If the battery is really dead after leaving the headlights on (and pulling fuses makes no difference in parasitic draw as you mentioned), my next step would be to pull the driver's side carpet and check for the typical corroded wire harness on the floor. It's very likely if you have a sun roof.
OP...
I have had vehicles with large alternators give enough of a surface charge to start the vehicle again after only a few minutes of run time.
Next time it acts up and you have to jump it, let it run a few minutes. Turn it off and start it again. If it starts, shut it down and turn on all the headlights for about 10 minutes and try restarting. If it starts up again, my guess would be an intermittent ground. In front of the driver's seat is a square patch of carpet you can pull up. Under that is the nut that secures your main ground cable. Make sure it's tight. From there, you'll need to lift the seat to check everything else under there...there's far more than just a battery under the seat. Testing voltage under the hood and jump starting from there is bypassing any weak grounds or positive cable connections to your battery.
If the battery is really dead after leaving the headlights on (and pulling fuses makes no difference in parasitic draw as you mentioned), my next step would be to pull the driver's side carpet and check for the typical corroded wire harness on the floor. It's very likely if you have a sun roof.
08-27-2018, 01:55 PM
#20
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Location: Spring Lake, NJ, US of A
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I agree with having an accurate meter, and that the "Free with coupon" H/F one is adequate (I have 5 or 6 of them).
A halfway decent set of triple squares is essential to working on one of these.
But tests 3 & 4 won't show anything. I hope you mean positive jump terminal & negative on battery, and pos on battery and neg under hood.
One more test that is absolutely imperative is to 'load test' it.
What does the battery (measured AT the battery) show when trying to crank it?
What do the jump posts show when trying to crank it?
As was noted, the fact that it will jump start from a totally dead battery, then start just fine a minute or two later is a big clue.
Knowing both battery voltage and 'system' voltage under those two situations will tell you a lot.
I'm going to guess that the ground connection between the battery and the chassis is marginal.
I will guess that the battery voltage is good, and doesn't drop when it's "dead".
This is a widely known problem in the 928 and exhibits the exact same symptoms.
A halfway decent set of triple squares is essential to working on one of these.
But tests 3 & 4 won't show anything. I hope you mean positive jump terminal & negative on battery, and pos on battery and neg under hood.
One more test that is absolutely imperative is to 'load test' it.
What does the battery (measured AT the battery) show when trying to crank it?
What do the jump posts show when trying to crank it?
As was noted, the fact that it will jump start from a totally dead battery, then start just fine a minute or two later is a big clue.
Knowing both battery voltage and 'system' voltage under those two situations will tell you a lot.
I'm going to guess that the ground connection between the battery and the chassis is marginal.
I will guess that the battery voltage is good, and doesn't drop when it's "dead".
This is a widely known problem in the 928 and exhibits the exact same symptoms.
The next step would be if - there is no drop showing between the 3 & 4 tests - repeat the test with the engine cranking. Given the size of the wire - I would expect no more than 0.25V difference. More than that indicates a high resistance connection or wire.
08-27-2018, 02:02 PM
#21
I over looked some information. Porsche does not want you to pull the fuses as it can wake up the vehicle. The proper method is as follows: my pictures did not load. 
They appear to be in my post pictures, not sure. Go to my profile and you can see them.
Beyond a parasitic draw, things I've seen cause interment starting issues like you've described are: bad DME relay, and once a start that didn't have the cable fully tightened caused an issue once the vehicle got hot it wouldn't start.
I think what is important here is to verify the vehicle electrical, charging, and starting systems are all working properly before moving onto diagnosing a parasitic draw. Testing at the battery posts, not the jump posts. Open circuit voltage tests don't really tell us much except the battery needs to be charged. Until this is done I wouldn't really start tearing into a draw issue. Also pull the fault codes.
They appear to be in my post pictures, not sure. Go to my profile and you can see them.Beyond a parasitic draw, things I've seen cause interment starting issues like you've described are: bad DME relay, and once a start that didn't have the cable fully tightened caused an issue once the vehicle got hot it wouldn't start.
I think what is important here is to verify the vehicle electrical, charging, and starting systems are all working properly before moving onto diagnosing a parasitic draw. Testing at the battery posts, not the jump posts. Open circuit voltage tests don't really tell us much except the battery needs to be charged. Until this is done I wouldn't really start tearing into a draw issue. Also pull the fault codes.
Last edited by Ptech; 08-27-2018 at 02:44 PM.
08-27-2018, 02:36 PM
#22
Burning Brakes
If you can have a sub and battery, or a sub and spare, why can't you have all three since the battery fits under the sub to begin with? Did Porsche use a smaller sub when equipped with a spare leaving no room for the battery? I'm looking to add a spare to my Cayenne with sub but no 2nd battery and would hate to find out that I'd also need a smaller sub.
....
....
This excerpt from the service manual for my 2004 has some not-so-clear wording (typical for that document), but the pictures tell the story pretty well. The sub that goes over the second battery takes up almost all the space in there.
08-27-2018, 03:37 PM
#23
Burning Brakes
Yes, the subs are different.
I once pulled the sub to see if a battery was underneath it and didn't think there was a whole lot of space under there.
08-27-2018, 05:13 PM
#24
Nordschleife Master
Test 3 and 4 will show if there is any voltage drop in the circuit between the battery and the engine compartment. You can assume voltage drop by the readings from 1 & 2, but 3 & 4 are really what tell the story. If there is a ~1V drop (or more) between the battery positive and the jumper positive under the hood - something is seriously wrong. Ditto on the negative. Multiple tests like this help to narrow down the scope for the next step in troubleshooting. You mention 2 guesses - these tests will confirm or disprove those guesses with actual data.
The next step would be if - there is no drop showing between the 3 & 4 tests - repeat the test with the engine cranking. Given the size of the wire - I would expect no more than 0.25V difference. More than that indicates a high resistance connection or wire.
The next step would be if - there is no drop showing between the 3 & 4 tests - repeat the test with the engine cranking. Given the size of the wire - I would expect no more than 0.25V difference. More than that indicates a high resistance connection or wire.
Test 3 says to put the probes on both positives.
Test 4 says to put them on both negatives.
Unless I'm really missing something, that would show nothing on the meter.
You'd have to go positive battery to negative jump post and pos post to neg batt to see what you are looking for, wouldn't you?
And I fully agree testing, actual data is far, far superior to guessing.
08-27-2018, 06:29 PM
#25
Ok, I'm either misreading or misunderstanding.
Test 3 says to put the probes on both positives.
Test 4 says to put them on both negatives.
Unless I'm really missing something, that would show nothing on the meter.
You'd have to go positive battery to negative jump post and pos post to neg batt to see what you are looking for, wouldn't you?
And I fully agree testing, actual data is far, far superior to guessing.
Test 3 says to put the probes on both positives.
Test 4 says to put them on both negatives.
Unless I'm really missing something, that would show nothing on the meter.
You'd have to go positive battery to negative jump post and pos post to neg batt to see what you are looking for, wouldn't you?
And I fully agree testing, actual data is far, far superior to guessing.
08-27-2018, 08:17 PM
#27
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EXACTLY.
If there is ANY difference - you know where to start looking. And repeating it with the starter cranking measures any drop UNDER LOAD - which is important. A high resistance flaw may show no drop with no load going through it - but with a load through it (starter current) - the drop will show if it's there.
If there is ANY difference - you know where to start looking. And repeating it with the starter cranking measures any drop UNDER LOAD - which is important. A high resistance flaw may show no drop with no load going through it - but with a load through it (starter current) - the drop will show if it's there.
08-27-2018, 10:52 PM
#28
Yep. You just need to make sure that your multimeter has good enough resolution to reflect the drop in voltage under load if it is not sustained for very long. Many cheap ones don't do so well with transient voltage measurements.
08-27-2018, 10:55 PM
#29
Also, if you follow the directions posted earlier by PTEC and put the MM in series with your battery, make sure you are ONLY measuring the parasitic drain. If you try to activate the starter like this (or maybe even turn on your ignition and the air compressor, blower fan, etc. all activate, you may let the magic smoke out.
08-28-2018, 05:56 AM
#30
Sorry, I didn't get a notification by email as usual about all these replies so I've just seen them now after coming back from the morning run to drop my daughter off.
I will read them all properly and follow the instructions but this is what I did this morning (before seeing the messages).
The battery was flat. It was reading 8.40 or so (sorry, because I'm talking my daughter to her grandparents and she's sat there in the buggy waiting I'm not making 100% accurate notes). That was on the posts. When I read it with the positive terminal and another grounded part of the car it read as 10-something. Then, like yesterday, the battery also read 10-something too...
I jump started it then turned it off. As was suggested, I did try the hatch release button but nothing at all. To be honest, I don't think that works (I didn't even know it was there - but I do remember a few weeks ago pulling a small physical piece out by mistake behind the cd changer, I had no idea what it was - but now I'm wondering if it's to do with the release?). But the button didn't work after driving, or with the engine running in park, or any combination I could think of, so I don't think it does work.
I started the car again (sorry, I literally cannot remember now if it started without another jump or not...)
Then I set off. It's a 25 km (15 mile) round trip, with the car stopped half way for a few minutes. It restarted fine.
When I got back. I turned the engine off and the electrics but left the key in. Waited a bit, then restarted. No problem.
I repeated this 4 or 5 times.
Then I took the key out. Waited a few seconds, put it in and restarted. I repeated this 4 or 5 times taking the key out each time.
Then I took the key out, locked the car, and waited a minute or two. Unlocked the car, and it started fine again.
I turned it off and checked the voltage and it was ready 12.37 on the posts.
Again, I hadn't seen these messages until now, but I will check the ground cable first as a priority (I have to do some work first but I'll go down to the car in an hour or so).
Thanks everyone for the help. It really is appreciated. Really hope we can get to the bottom of this!
I will read them all properly and follow the instructions but this is what I did this morning (before seeing the messages).
The battery was flat. It was reading 8.40 or so (sorry, because I'm talking my daughter to her grandparents and she's sat there in the buggy waiting I'm not making 100% accurate notes). That was on the posts. When I read it with the positive terminal and another grounded part of the car it read as 10-something. Then, like yesterday, the battery also read 10-something too...
I jump started it then turned it off. As was suggested, I did try the hatch release button but nothing at all. To be honest, I don't think that works (I didn't even know it was there - but I do remember a few weeks ago pulling a small physical piece out by mistake behind the cd changer, I had no idea what it was - but now I'm wondering if it's to do with the release?). But the button didn't work after driving, or with the engine running in park, or any combination I could think of, so I don't think it does work.
I started the car again (sorry, I literally cannot remember now if it started without another jump or not...)
Then I set off. It's a 25 km (15 mile) round trip, with the car stopped half way for a few minutes. It restarted fine.
When I got back. I turned the engine off and the electrics but left the key in. Waited a bit, then restarted. No problem.
I repeated this 4 or 5 times.
Then I took the key out. Waited a few seconds, put it in and restarted. I repeated this 4 or 5 times taking the key out each time.
Then I took the key out, locked the car, and waited a minute or two. Unlocked the car, and it started fine again.
I turned it off and checked the voltage and it was ready 12.37 on the posts.
Again, I hadn't seen these messages until now, but I will check the ground cable first as a priority (I have to do some work first but I'll go down to the car in an hour or so).
Thanks everyone for the help. It really is appreciated. Really hope we can get to the bottom of this!