I found damage to the wire that goes into the firewall from the single-wire plug of the O2 sensor. I hadn't realized it was coax cable.

The outer copper shield has pulled out of the plug and the inner wire is damaged. Easy enough to reconnect the inner; not sure what to do about the outer - or if I can leave ~ 2" of it unshielded.

(from Wiki) "coaxial cable a good choice for carrying weak signals that cannot tolerate interference from the environment or for higher electrical signals that must not be allowed to radiate or couple into adjacent structures or circuits."

Questions/comments:

1. If shielding from interference is important for the <= 1-volt signal, why is the wire up from the sensor unshielded?

2. Is it coax from the plug in because it needs protection from all the voltage in the harness? If so, I should be able to leave it exposed before it enters the harness.

3. Replacement would require opening and retaping the harness. Or I could find a way to splice back in to the shielded plug.



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240 drivers / parts cars - JH, Ohio

are you sure it's coax? I always thought it was just a heat shield, in which case any connectivity it has (or loses) wouldn't matter.

by Coax I mean "an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield ... typically one to four layers of woven metallic braid " ie. the woven outer braid doesn't have to be used as a conductor to be called coax (I think).

The 240 O2 cable is 4 layers -wire, insulation, woven braid, outer sheath.

Note though that it isn't a heat shield ie. the wire coming up from the exhaust is an insulated single wire, with 2 others in a plastic sheath.

It's the wire from the sensor in through the firewall that's coax. Because it is subject to interference I assume.
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240 drivers / parts cars - JH, Ohio