Any '99 Boxster owners in RI???

I'm pulling this from the original thread in the "parts wanted" board, since it really doesn't belong there.

http://pedrosboard.com/read.php?6,1076,1076#msg-1076

Two mechanics (one at the dealer) have concluded that the DME is faulty. But neither is positive on this... Here's the recap:

I've got 7 codes right now. Since the problem began I've had up to 16 at once. I've replaced the O2 sensors per my mechanic's recommendation but still have short circuit codes for all of them. I have a cylinder 5 misfire code, but have seen codes for all 6 cylinders in the past. (I haven't replaced any coils because of this fact, although the presence of only one misfire code makes me want to replace the coil on 5.)

P0132 Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 - 3) - Short Circuit to B+
P0152 Oxygen Sensor Ahead of Catalytic Converter (Cylinders 4 - 6) - Short Circuit to B+
P0138 Oxygen Sensor After Catalytic Converter (Cylinders 1 - 3) - Short Circuit to B+
P0158 Oxygen Sensor After Catalytic Converter (Cylinders 4 - 61 - Short Circuit to B+
P1128 Oxygen Sensing Adaptation Area 2 (Cylinders 1 - 3) - Rich Threshold
P1124 Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Rich Threshold
P0305 Misfire, Cylinder 5, Damaging to Catalytic Converter

My mechanic and the dealer supposedly checked the wiring for shorts/breaks independently. I've had the CEL on for a year now and haven't been able to get my car inspected as a result... boy would I love to solve this problem!



Edited 1 time(s). Last edit at 03/30/2011 08:26PM by Jayusa123. (view changes)

So, I'm back at it once again. Hoping to FINALLY get this sorted out. I would really prefer to know more about the true cause of the problem before I through more money at it in the form of a new (well, used) DME.

I took the car for a drive and logged information with an OBD II scan tool. I'm hoping someone can help me understand the situation a little better. Before I left for the drive I idled at operating temperature. All four O2 sensors were flat lining at 1.115v and I couldn't seem to make them budge with revving. (makes sense considering the short circuit codes--which I still have.) I took the car around the neighborhood with a max. speed of 33mph. After returning, I reviewed the data, and I was surprised to actually see some activity on one of the O2 sensors (1/1). The other 3 O2 sensors flat lined at what I assume is a maximum value (?) of 1.115v.

Below is a snapshot of the ranges for the drive. Do any look out of sorts? Unfortunately I can't export the values to charts on the computer, I can only access them on the tool, but if you would like to know what all the sensors were reading at a particular point in time, I can provide that info.

Thanks, all!

Jay

Speed: 0 - 33 MPH

Tach: 780 - 4500RPM

O2 1/1: .3v - 1.115v
O2 1/2: 1.115v (flat line)
O2 2/1: 1.115v (flat line)
O2 2/2: 1.115v (flat line)

MAF: .5 - 7.5 LB/M

It sounds to me like you have a pinch/chafe/crush/etc. in your wiring harness. The max output of the O2 sensors is supposed to be 1.0v.

Since the O2 sensors are showing errors, that is a good place to start. Bad O2 sensor readings can cause misfires on random cylinders.

Here is the diagnostic procedure for checking the wires. I would not assume that either mechanic did it right. Also, the problem may be intermittent. When checking the wiring you should jiggle everything with the meter connected. There isn't that much wire between the DME and the sensors.

In any case, I would start with the Porsche-recommended procedure for P0138.

1. Check wiring harness .
Remove all the four oxygen sensor connectors.
Switch ignition on.
Connect voltmeter at sleeve to pins 3 and 4 of oxygen sensor connector 1 behind catalytic converter. Specified Value: approx. 450 mV
Connect voltmeter at sleeve to pin 3 and ground. Specified Value: approx. 720 mV . If the measurement according to items 3 and 4 does not show the specified values, remove ECM connector and check wires for short circuit to plus. If no short circuit to plus can be detected, replace ECM.

2. Check oxygen sensor .
Remove oxygen sensor connector 1 behind catalytic converter.
Connect ohmmeter on pin side to pins 1 and 3 of the oxygen sensor connector. Specified Value: Infinity Ohms .
Connect ohmmeter on pin side to pins 2 and 3 of the oxygen sensor connector. Specified Value: Infinity Ohms .
Connect ohmmeter on pin side to pins 1 and 4 of the oxygen sensor connector. Specified Value: Infinity Ohms .
Connect ohmmeter on pin side to pins 2 and 4 of the oxygen sensor connector. Specified Value: Infinity Ohms. NOTE: This check must be performed on the cold engine.

Quote
Jayusa123
So, I'm back at it once again. Hoping to FINALLY get this sorted out. I would really prefer to know more about the true cause of the problem before I through more money at it in the form of a new (well, used) DME.

I took the car for a drive and logged information with an OBD II scan tool. I'm hoping someone can help me understand the situation a little better. Before I left for the drive I idled at operating temperature. All four O2 sensors were flat lining at 1.115v and I couldn't seem to make them budge with revving. (makes sense considering the short circuit codes--which I still have.) I took the car around the neighborhood with a max. speed of 33mph. After returning, I reviewed the data, and I was surprised to actually see some activity on one of the O2 sensors (1/1). The other 3 O2 sensors flat lined at what I assume is a maximum value (?) of 1.115v.

Below is a snapshot of the ranges for the drive. Do any look out of sorts? Unfortunately I can't export the values to charts on the computer, I can only access them on the tool, but if you would like to know what all the sensors were reading at a particular point in time, I can provide that info.

Thanks, all!

Jay

Speed: 0 - 33 MPH

Tach: 780 - 4500RPM

O2 1/1: .3v - 1.115v
O2 1/2: 1.115v (flat line)
O2 2/1: 1.115v (flat line)
O2 2/2: 1.115v (flat line)

MAF: .5 - 7.5 LB/M

The tip of the sensor are covered with metal electrodes that react to create voltage ony if the ambient air has a higher oxygen content than the exhaust and the tip is at 575F.

When they are not yet up to temperature they emit a voltage of 0.45v.

If the exhaust has very little to no oxygen the sensor should emit a voltage very close to 1v.

If the exhaust has a lot of oxygen very close to ambient air the sensor should emit a voltage very close to 0v.

Normally the sensors have a voltage swing of between 0.1 volts to 0.7 volts. The swing arises from the Ecu constantly varies the amount of fuel it injects first injecting a bit (and I mean a bit, a tiny bit) too much then another tiny bit too little.

If the engine is running lean the exhaust gas has about the same amount of oxygen as ambient air so the sensor would generate very little to no voltage, though generally (under normal conditions) around 0.1v

If the engine were running rich the oxygen content of the exhaust would be much lower than ambient air and the sensor voltage would be larger, though generally no more than 0.7 to 0.8 volts (under normal conditions).

Or to put it another way, with an air:fuel ratio of 11.78:1 (very rich) the voltage level would approach 1v. With an air:fuel ratio of 17.66:1 (very lean) the voltage approaches 0 volts.

If a properly heated sensor were operated in ambient air it would generate a voltage of about 1 volt. 'about 1 volt' is close (?) to 1.115v. This might suggest the sensors were exposed to a big exhaust gas leak letting in prodigous amounts of ambient air. I would think an exhaust leak of this size though would be obvious.

Another source of ambient air could be a secondary air pump that was running and its output was suppling the outside air. But you would I assume hear the pump running.

Otherwise, if there is no ambient air leak then a 1.115v suggests to me there is some kind of wiring short or break and the Ecu is essentially receiving a max. reading on its sensor input or a minimum reading.

IMPORTANT: Please note I typed the stuff in below verbatim but note the differences of the test steps. Read the steps through several times and note/highlight the differences. Since I typed it in as it was printed, that tech service note about doing the checks with the engine cold is at the very end of this email cause that was where the tech. service note was located at the end of all the tests.


Let's see...

P0132 - oxygen sensor ahead of converter (bank #1 - cyls 1-3) shorted to positive.

The error code is stored when the sensor voltage is above 1 volt for more then 30 seconds without interruption.

Note in case of a short circuit to positive at one oxygen sensor, all 4 sensors will be stored. Also the fault may cause misfires.

Wiring harness test:

Remove [sic] [disconnect?] all 4 sensor connectors.

Turn the ignition to on.

Connect a digital volt meter to pin 3 and 4 of the sensor connector 1 ahead of the converter. Read approx. 450mV.

Connect a digital volt meter to pin 3 and 4 of the sensor connector 1 ahead of the converter. Read approx. 720mV.

Please note the above step differs from as near as I can tell the same test performed for P0152. I do not know if the tests really are different or there is a misprint in my reference. I suspect there is a misprint. But you are on your own.

Note: Do not use ECM (DME) ground to avoid possibly damaging the ECM or other components.

If no short is detected the ECM may need replacing.

Sensor test:

Remove [disconnect?] bank #1 sensor connector ahead of converter.

Connect digital ohmmeter to pin 1 and 3 of the sensor connector. Read infinity.

Connect a digital ohmmeter to pin 3 and 2 of the sensor connector. Read infinity.

Connect a digital ohmmeter to pin 4 and 1 of the sensor connector. Read infinity.

Connect a digital ohmmeter to pin 4 and 2 of the sensor connector. Read infinity.


For P0152 - oxygen sensor ahead of converter (bank #2 - cyls 4-6) shorted to positive.

The error code is stored when the sensor voltage is above 1 volt for more then 30 seconds without interruption.

Note in case of a short circuit to positive at one oxygen sensor, all 4 sensors will be stored. Also the fault may cause misfires.

Wiring harness test:

Disconnect all 4 sensor connectors.

Turn the ignition to on.

Connect digital volt meter to sleeve pin 3 and 4 of the sensor connector 1 ahead of the converter. Read approx. 450mV.

Connect a digital volt meter to sleeve pin 3 and ground. Read 750mV.

Note: Do not use ECM (DME) ground to avoid possibly damaging the ECM or other components.

If the measurements above do not supply the right values remove the ECM connector and check the wires for a short circuit to positive.

If no short circuit to positive can be detected, the ECM may need replacing.

Sensor test:

Remove [disconnect?] bank #2 sensor connector ahead of converter.

Connect a digital ohmmeter to the pin side of pin 1 and 3 and the sensor connector. Read infinity.

Connect a digital ohmmeter to the pin side of pin 2 and 3 of the sensor connector. Read infinity.

Connect a digital ohmmeter to the pin side of pin 1 and 4 of the sensor connector. Read infinity.

Connect a digital ohmmeter to the pin side of pin 2 and 4 of the sensor connect. Read infinity.

Tech service note: The check must be performed with the engien cold.

If you need more help, if you think I can be of more help PM me and we'll talk by phone.

Added: I see Boxsterra beat me to the punch/post. Admin delete this if you want.

Sincerely,

MarcW.



Edited 1 time(s). Last edit at 03/30/2011 11:12PM by MarcW. (view changes)

Where are you and Stefan getting your info? Alldata?

J

1996 - 2004.

I also have a full set (over 60lbs!) of the Boxster factory manuals but they're buried under my office desk so I tend to use the Engine Guide even though it has some obvious typos. I just don't have room in my office for enough shelf space to have all my references handy.

I also have a set of 996 Turbo OBDII manuals and even a set of Carrera GT OBDII manuals.

Sincerely,

MarcW.

I have the Bentley manual, but that doesn't do much for troubleshooting. I've been thinking of going for Alldata since it has the factory manual stuff without the storage requirement you mentioned!

jay

Their interface is a little difficult to navigate and their information isn't 100% complete but I do find it to be a valuable reference and it is online, which is convenient.

I bought alldata when they offered a "deal". What a crock. Zero info, and hard to navigate. Much looked like (bad) scans of the Bentley. Huge gaps in info.

Yuk.

Grant

Before I bought another DME, I would try to further isolate both the harness and the DME.

Boxsterra clearly knows the proper test procedures. Given enough time and know how, they will certainly work.

I am a little more plebeian... I would remove your DME and insert it in a near identical car. If possible put the known good unit in your car. Either test requires a friend, but the test would take little time and give you a fairly clear answer.

It sounds to me as likely that the harness is bad vs. the DME.

That would be ideal. Although, how would it work with the security system? We'd probably have to swap both the DME and the immobilizer in order to test it under plug-and-play conditions. Otherwise we'd have to get the dealer involved with the swap... we probably want to avoid that trouble!

I've advise against this DME swap.

Even if you are desparate and flush with money (or are the gambling type) I don't think it would work. IIRC (and I don't remember the details) you can't swap one DME for another even if the two are otherwise identical.

Plus there is always the risk of damaging one maybe two good DMEs with static discharge. Or if the car's got a wiring problem that has damaged the DME and this accounts for the problems you are seeing, plugging in a donor DME might have this damaged too.

Sincerely,

MarcW.

If there is some reason the DME won't work in another car -- security or whatever then you are stuck with the testing procedures.

I guess you have to do it right.

I would be less worried about static. just maintain proper protocol. Think like you are changing a board in the computer.



Edited 1 time(s). Last edit at 04/04/2011 09:00AM by JMstamford,ct. (view changes)

DME from an earlier Boxster, the sickness being a memory checksum error IIRC, with the DME replacement cost over $5K (not a typo!) I checked in with the local Porsche dealer parts manager: the price was confirmed; later models have a less expensive DME (<$2K IIRC.

Furthermore, the techs told me what while a donor DME could be used but one has to know the VIN from the car it came from and there's some DME/security setup that has to be done (using PST2 or PIWIS nowadays I guess) in order to the donor DME to work with the car it did not originally come from the factory with. Then of course to revert the sick car back to at least being able to work with its original DME this all has to be undone.

If you want to check with a qualified professional Porsche tech in your area to confirm my memory I have no problem with that. If I'm wrong (or right) feel free to post what you learn. We all benefit.

Sincerely,

MarcW.

You can program the new DME to work with the immobilizer. And you can swap to two DMEs back and forth. There is nothing to do to use the old DME again since it has not been programmed.

Furthermore you can get a DME for under $500 as long as you don't go to a rip off place.

given. I never had any reason to doubt it and certainly not any reason to verify it.

If what you say is correct, then the OP has less in his way if he wants to get a donor DME and see if it cures the original symptoms. As for the price, there may be low-cost DMEs available. I haven't looked for any. I was quoting the price I was quoted at the dealer's parts department.

If a new DME can be had for $500 that's a very reasonable price compared to the $5K price I was quoted for early Boxsters and even the $2K price I was quoted for a 2000 MY and later Boxster.

Sincerely,

MarcW.

Suggest a non-rip-off place for him....

The problems you are experiencing can be diagnosed by a mechanic with electronics knowledge.

If you swap the DME and it works, what does that tell you? (I say, nothing)
If you swap the DME and it doesn't work, what does that tell you? (I say nothing)
As soon as the circuit shorts again, the problem will recur and damage to the new DME will be risked.

hope you figured out what was wrong, I also need a little heelp with my 02 sensors, I replaced all four of them not too long ago because of a CEL.
I still get that same cel telling me the same 02 sensor is bad with a new sensor in there, not that big of a deal right now.
My issue is I bought a set of OBX headers on amazon, they sent me the headers without 02 bungs. I need to get the headers
drilled and have bungs welded on, does anyone know the size of teh threads on the sensors? I went to autozone and they gave me one
that was the size of a scud missle for reference, it just didnt feel like it was the right size.

so I can't dig out an old O2 sensor from my 02 Boxster and measure the thread diameter and pitch.

But if you have an access to a micrometer or a dial/venier caliber (not the most accurate measurement tool) and a metric rule and an old sensor you can measure the threads yourself. You can even buy a thread pitch gage though I have no idea how much these cost nowadays. They weren't too expensive and pretty handy to have around to identify various metric (or inch) threads.

Or take the headers to the shop along with a sensor and tell them to drill the bungs then tap them to fit the sensors after they weld the bungs in.

Sincerely,

MarcW.

the O2 sensor thread size: 18 x 1.5.

Sincerely,

MarcW.

thanks Marc! I would normally have the guy put it on the lift and pop one off but I didnt have the car with me.