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Here are pics to wire the cap to the passenger side downstream O2 sensor. Note the upstream (before) cat O2 sensor connector with BLUE protective sleeve is below the downstream connector. The two white wires are for the O2 sensor heater. DO NOT touch the white wires.
To experiment what cap value works for your car's cat condition, I recommend using T-taps (look up on internet) to splice into the black and gray wire separately without cutting them to try the different value caps.
I recommend experimenting with TWO sets of 4.7, 47, and 470 uF (commonly avail values). If the caps are polarized, pay attention to the polarity (+/-) when wiring. My car needed the 4.7uF for the passenger cat and 470 uF (100x!) for the driver side. I suspect the driver side cat is worse from the not-so-well designed 1st gen Air-Oil-Separator (AOS) dumping more oil to the driver side bank (bank 2) via the turbo/intercooler hose. The catch can and filters (in pic) are to reduce the oil getting into the intake. I tried replacing the diaphragm only ($35 on line), and it made situ worse as the aftermarket diaphragm is slightly smaller than factory version. I ended up replacing with a genuine Porsche AOS ($170) plus added the catch can/filters to increase protection.
First remove the driver side beauty cover Then remove the firewall beauty cover Here's the passenger (right, bank 1) side downstream O2 sensor connector. Note the 4.7uF is temporarily wired to the signal wire (black) and signal ground wire (gray). Note it is NOT necessary to cut the black or gray wire. The black wire was cut when trying the in-line diode method, which didn't work completely. A closer look at the temp setup. The cap is now soldered to the signal + (black) wire. Note again it is NOT necessary to cut the wire to connect cap. Using a wire-stripper (18 gauge) or a razor blade, carefully pull the vinyl sleeve apart to expose the wire. Wrap the cap wire to the exposed wire, solder, and tape with electrical tape. Connect cap to signal ground (gray) wire using the same method. Add wire loom to protect (and conceal) fix. Plug connector back to car ECU plug. Done!
Here are pics to wire the cap to the passenger side downstream O2 sensor. Note the upstream (before) cat O2 sensor connector with BLUE protective sleeve is below the downstream connector. The two white wires are for the O2 sensor heater. DO NOT touch the white wires.
To experiment what cap value works for your car's cat condition, I recommend using T-taps (look up on internet) to splice into the black and gray wire separately without cutting them to try the different value caps.
I recommend experimenting with TWO sets of 4.7, 47, and 470 uF (commonly avail values). If the caps are polarized, pay attention to the polarity (+/-) when wiring. My car needed the 4.7uF for the passenger cat and 470 uF (100x!) for the driver side. I suspect the driver side cat is worse from the not-so-well designed 1st gen Air-Oil-Separator (AOS) dumping more oil to the driver side bank (bank 2) via the turbo/intercooler hose. The catch can and filters (in pic) are to reduce the oil getting into the intake. I tried replacing the diaphragm only ($35 on line), and it made situ worse as the aftermarket diaphragm is slightly smaller than factory version. I ended up replacing with a genuine Porsche AOS ($170) plus added the catch can/filters to increase protection.
First remove the driver side beauty cover Then remove the firewall beauty cover Here's the passenger (right, bank 1) side downstream O2 sensor connector. Note the 4.7uF is temporarily wired to the signal wire (black) and signal ground wire (gray). Note it is NOT necessary to cut the black or gray wire. The black wire was cut when trying the in-line diode method, which didn't work completely. A closer look at the temp setup. The cap is now soldered to the signal + (black) wire. Note again it is NOT necessary to cut the wire to connect cap. Using a wire-stripper (18 gauge) or a razor blade, carefully pull the vinyl sleeve apart to expose the wire. Wrap the cap wire to the exposed wire, solder, and tape with electrical tape. Connect cap to signal ground (gray) wire using the same method. Add wire loom to protect (and conceal) fix. Plug connector back to car ECU plug. Done!
I just ordered this kit and will try to tackle the passenger side tomorrow
Electrolytic Capacitor 4.7uF 47uF 470uF 10V 16V 25V 50V 63V 100V 160V 200V 250V 400V 450V Capacitors Kit 18Value 270Pcs for Repair Household Appliances Communication Equipment Electronic Toy https://a.co/d/4aCt2VW
The cap voltage rating is less important as we are dealing with less than 5V. The cap temperature rating is more important to withstand under hood temperature. I recommend using caps that are rated >85C (>176F).
The cap voltage rating is less important as we are dealing with less than 5V. The cap temperature rating is more important to withstand under hood temperature. I recommend using caps that are rated >85C (>176F).
Best wishes and may the Force be with you!
how did you test if it worked? Did you drive and see if it came on? Or did te CEL instantly come on if the UF was wrong
Thanks for the very nice solution and presentation!
If the 470 uF worked on one side, shouldn't it also work on the other side, which you used 4.7 on? If so, then you could go straight to that value without needing to test as you did, now that you know the 470 uF is enough but not too much. What do you think?
Will definitely be filing this page away for future reference.
To nail down the correct cap value, you will need a OBD-II reader. A simpler reader ($30 or auto parts rental) will do. Make sure there are no other CEL codes. If there are, should address/fix those error codes first to prevent/eliminate false conclusions.
Here's what I did:
1. Cleared the P0421 and/or P0431 CEL codes using the OBD-II or equivalent reader
2. Wired in the 4.7 uF cap on each side downstream O2 sensor signal and ground wire (i.e., parallel to each O2 sensor)
3. Drove SUV for 30'ish miles to allow partial setting of OBD-II monitoring. (FYI, full OBD-II monitoring requires 75-100 miles.)
4. Checked for PENDING (not stored yet) P0421/0431 (bank 1/2) codes using OBD-II reader.
5a. If there were no pending codes, kept on driving until 75 miles total or more to see if CEL comes on or use OBD-II reader to check for PENDING code.
5b. If pending code(s) appeared, replaced bank 1 (P0421) and/or bank 2 (P0431) cap to next higher (x10) value. As I learned, bank 1 and bank 2 may require different cap values.
As of this writing, I have driven over 420 miles with the 4.7/470 uF (bank 1/2) combo with no CEL or cat efficiency pending codes.
Thanks for the kind words. I just wanted to return the favor in this forum as other postings here had helped me fixed other problems in my Porsches.
To respond to your question, I can't say if one size (470 uF) fits all. In my car's case, I surmised bank 2 (driver side) cat is in worse shape than bank 1 thanks to the subpar AOS design. What I do know is the ECU will throw the CEL if it doesn't see 'expected' activity from an O2 sensor. Learned that when I used the silicone diode when any activity below 0.7V was suppressed/flatlined. I think the error code was O2 sensor heater not functioning, probably triggered from cold start and warm up. (I have come to respect the diabolical geniuses who developed the OBD-II s/w.)
Need more previous diagnostic info about your car. Did both P0421 (bank 1/passenger side) and P0431 were reported by OBD-II BEFORE you put the caps in? (If only the P0431 were the only code, your pass cat is fine.)
While the P0431 caused the CEL with the 4.7 uF caps, does the P0421 code popped up in the PENDING code? (If not, the 4.7 uF cap is likely the right value for the pass cat. Just need to put in more miles (>70) to confirm.
I see two options continuing your experiment: One is to increase the driver side cap value to 47 uF (10x), clear the CEL, and drive for another 30 miles to check BOTH cats. Two is to leave the two 4.7 uF in place and drive till 70-100 miles total to confirm pass cat issue has been resolved, i.e., no P0421. Then increase driver side cap value ONLY and clear the CEL to test again by driving other 30-50 miles.
It will be interesting to see if your driver cat condition is worse than pass cat like mine. My hunch of the cause is due to the subpar AOS feeding more oil vapor to the driver side intake and cat on how the return hoses are plumbed. FYI, it took me a month and >200 miles of testing before finding the right cap values. Patience is of virtue. Best wishes!
Part of this experiment is to determine how good/bad the cats on EACH vehicle. One cat may be in better/worse condition than the other hence requiring diff cap values. Since there is no easy way to quantify each cat health (even if the cat is removed from car), we are dealing with a black box (cat) situation along with complex varying impedance from the ECU and O2 sensor.
My wish is there is a customized (unique) solution set for everyone who is willing to invest test time and miles to avoid spending $3-5K to replace the cats.
Since P0156 means your driver downstream O2 sensor malfunctions (assuming you hadn't seen this code prior to the experiment), you may want to double-check your wiring on that (driver) side to make sure the cap + lead is connected to the BLACK wire and - lead to gray wire, assuming you are using polarized caps.
Since P0156 means your driver downstream O2 sensor malfunctions (assuming you hadn't seen this code prior to the experiment), you may want to double-check your wiring on that (driver) side to make sure the cap + lead is connected to the BLACK wire and - lead to gray wire, assuming you are using polarized caps.
Keep us posted.
ugh I’m an idiot then.
last night I swapped the passenger side to 47uf and swapped the polarity on the passenger side. Whoops.
ill fix it after work then. So negative side to grey on both which is the short side to grey according to my photo.
06-24-2022, 11:22 AM
