CE Light & Catalytic Converters

[dbear61]

Here’s a CEL puzzle on my 2001 Boxster S.

Last Summer, I was on a road trip through New England, and the CEL stayed on at start-up. Two stops later, the CEL is off at start-up. Three stops later, the CEL stayed on at start-up.

I continue the drive home with CEL constantly on. Back in WI, my local dealership analyzes the problem, and comes back with both catalytic converters need to be replaced. Pre-cat and post-cat sensors have the same readings. Quote is almost $7,000. That is not happening.

I had both cats replaced with after-market parts in 2016. For both to fail simultaneously? At the time this showed up, it was only six years, and probably about 30,000 miles. That doesn’t make sense to me.

I go back to my independent who did the replacement. “I’ll have to look into it.” A month later, the weather is starting to turn, so I just take the car home and store it for the Winter.

In April, I bring the car out of hibernation, and the CEL turns off after ignition. WTH? I drive about 150 miles around town in 5 or six trips, and it is still off. I stop at the dealer, and they claim it takes a while for the OBD to reset after being in hibernation (never took this long in the prior 10 years).

I go on my Route 66 road trip. Interstate, city, country, start, stop, high revs in each gear, low revs in each gear, low altitude, high altitude. The CEL is off the entire time. Then, 12 days and 3,200 miles into this varied-conditions trip, the CEL comes on at ignition.

Three days and 2,000 miles later, the CEL is still on. My friend has an OBD monitor with him, so he plugs it in, and it returns a code for Bank 1 catalytic converter not performing properly (I wish we had done this at the start of the tip to see if the OBD was active). Only Cat 1. He resets the OBD, and we finish our trip over 400 miles with multiple stops, driving conditions and temperatures. The CEL is still off. I do two local, five-mile drives, and it is still off.

I go to the dealer, and the service manager still thinks both cats are bad, that I haven’t driven enough conditions for the OBD to reset and recognize that both cats are bad.

I just do not think their conclusion is plausible. How do both cats, even if after-market, fail simultaneously after 6 years and only 30,000 miles without any Winter driving? Even if the OBD resets during storage, how do you drive 3,200 miles in multiple conditions before the OBD wakes up and sees something wrong?

I think there’s something wrong with the OBD, but my dealership is adamant that it is working, and I need to replace the cats.

I have since driven it short trips (about 5 miles) six more times, and the CE light still remains off.

What the heck do you think is going on?

DBear

[Homeoboxter]

I think if you are in doubts regarding your mechanics' judgement, you have two choices: you ask for a second opinion, or you do your own diagnostics. Diagnostics can easily be done with a Foxwell or Durametric tool, you can plot the O2 sensor voltage signal of all the four O2 sensors real time. This way you can have a pretty good idea about the efficiency of your cats. Without doing this all you can do is guessing. A Foxwell tool is ~ $150, a Durametric is more expensive, both can do the job. The other thing you need to invest is effort and time, to read some related articles and understand what to look for and how to interpret the results. Luckily, you can find all the help needed on this very forum, to do your own diagnostics. My two cents' worth.

[blue62]

What you need is a shop or person that has the ability to do an actual diagnosis of the issue.

"NOT" a shop that just replaces parts based on OBDII codes and profit margins.

There are numerous issues that can trigger OBDII catalytic converter "fail codes" that have nothing to do with the catalytic converters.

[dbear61]

It was an independent shop that replaced the cats 7 years ago,

It's the local Porsche dealership that is telling me both cats are bad and that the OBD probably went to sleep over the Winter storage, and that it can possibly take thousands of miles for the OBD to reset and start reporting again. I don't know how I could find any shop more qualified that the dealer, but it just doesn't seem logical that both cats would fail at the same time, nor that I could drive under so many different conditions for 3200 miles before the OBD wakes up again.

DBear

[Danimal]

Were the O2 sensors replaced with the cats?

[dbear61]

Originally Posted by Danimal

Were the O2 sensors replaced with the cats?

Only one was replaced. at the time the new converters were installed. The other three were working properly.

DBear

[mikefocke]

A CE is a generic fault. Ask or find out what the specific codes are. And 30kk with "aftermarket" cats and some old O2 sensors could result in cat destruction. Dump too rich stuff into a cat where the system isn't able to adjust the mixture and 30k miles is enough to cause all sorts of problems downstream of the engine.

Look at the exhaust pipe. How black at the tips?

You diagnose by looking at a o'scope and seeing how the voltages vary. Are the front ones varying within spec? Are the rear ones low and flat. How old is the MAF? Cleaned it with MAF cleaner recently? Are the sensors Bosch or Porsche parts (Porsche just labels them, Bosch makes em)?

I replaced O2 sensors in a pair so the freshness of the measurement was equal. Something any muffler shop can do with the right parts in 15 minutes a piece.