Carpokes Porsche Forum

A bunch of 993s had "biodegradable" engine wiring harnesses that, well, degraded. Except that they degraded much more rapidly than expected and caused all kinds of electrical maladies / batteries not charging / etc.

Porsche had a TSB on this and warrantied this work a long long time ago. Of course Porsche no longer warranties this work. I was reminded of this issue when I ran into someone who recently had a battery drain, replaced the alternator and battery, then STILL had a battery drain ..... and eventually replaced the engine wiring harness to finally solve the issue.

This issue was not exclusive to Porsche --- Mercedes had the same problem on many of its cars from the early 1990s as well.

Here is the TSB:
And here are pictures of the labels attached to my own harness (under the plastic cover on the driver's side of the engine bay.) You can see that the design date my my harness was in 1995, and the production date was in 2012, so luckily it was replaced before my ownership.

Good to know! Thanks much for the tip.

I had a 96 Targa that was covered under this TSB. Dealer replaced the harness free of charge. At the time I also had a 96 Coupe (track car) that had a different harness without the issue. The cars were built one month apart.

At the time I did receive a notice from Porsche to have the dealer inspect the harness.

Only sad point now, is that I have neither car...