All of the codes could have been set at the same time because they all get their power from the fuel pump relay. The power (12 volts) leaves the fuel pump relay, one branch to a 15 amp fuse, and to the fuel pump, the other branch goes to 4 fuses which feed all the things which have “shorted” codes.
It makes sense that the short happens somewhere between the fuel pump relay and before the first fuse on each of the branches. The short is probably not constant. A bare wire may touch ground (metal) momentarily—just long enough to set the codes. A short after a fuse(s) would blow that/those fuse(s).
You could have an auto parts store scan for codes, and erase any found. Then, you drive until the check engine light comes on, go to the auto parts store and have the scan done, again. This way, you could tell if the codes are getting set all at once, or piecemeal.
The wiring needs to be tested and examined between the fuel pump relay and the first fuses. It would help the repairer to know how the ECM (engine computer) senses the short(s).
OK. so to summarize, I was not ripped off by the replacement of the fuel pump relay.
Now, since the CEL light is back on, my dilemma is whether to go back to the VW dealer since he already performed the initial CEL scan (maybe they won’t charge me for another since I’ve raised such a stink already) and see what happens
OR
start over and take it (along with the codes) to a independent VW guy who may have more expertise and may be less expensive also
An update follows. First a summary. Took my car to the VW dealer for a new tire and also mentioned the CEL was on about a week ago but then went off. They did a scan and came back with 12 fault codes (listed specifically in a previous post) and recommended a new fuel pump relay, which they replaced. A few days later the CEL came back on.
Ok at first I was pretty angry but in the end I decided to take it back to VW (today). They performed another scan and came back with only 2 fault codes this time (woohoo!) so I guess the relay did fix something.
The only previous code that returned was P1136: Long term fuel trim too lean. (the fact that a fuel pump relay wouldn’t fix this fault was predicted by previous posts)
The tech said oxygen was getting into the engine somewhere and recommends replacing some vacuum hoses and tubes. I say SOME but the list he showed me included more hoses and tubes than I knew existed in a car. Total bill: close to $500. Wow.Those are some expensive hoses, I mean not the kind you buy at a hardware store I guess.
The second code that came back was more ominous: catalytic converter. The tech did say however that the extra air getting into the system could be preventing the CC from working correctly, and if the first fault is fixed the second fault may resolve on its own.
What I would do is verify any vacuum leaks by connecting a vacuum gauge. It’s a cheap, easy to use gauge that can reveal many things about an engine.
It takes a whopping 10-15 seconds to connect one up and will reveal instantly if there’s even a vacuum leak involved in this problem. If it appears a vacuum leak is present then it’s a simple matter of gently pinching off vacuum hoses until the leak disappears. That will at least narrow it down to a particular vacuum circuit and it can be repaired rather than using a shotgun approach by replacing everything.
The only down side is that many mechanics do not use a vacuum gauge and I can’t explain that.