I'm currently taking apart an old vehicle which was just lying around. While dismantling the exhaust manifold, I noticed there was a cable that connects to its base, right before the point where it connects to the exhaust pipe. I couldn't find the socket to properly disconnect it at that time so I just snipped the cable.

Please I'd like to know if that cable has any significant purpose. My guess is it's some kind of sensor. If so what sensor is it? And what are the downsides of driving without that sensor?


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  • 1
    That's the Oxygen Sensor signal wire that goes back to the ECU.
    – Moab
    Apr 16, 2020 at 12:17

2 Answers 2


Sounds like the oxygen or lambda sensor.

If fitted then it is needed as part of the fuel injection control circuit to achieve a correct air/fuel ratio.

There is usually a plug and socket to enable replacement of the sensor at some shortish distance from the sensor.

  • Thanks. But how is it going to achieve the correct air/fuel ratio if it's in the exhaust manifold? Shouldn't it be in the intake manifold instead?
    – Caleb
    Apr 13, 2020 at 13:09
  • @DarkNRahlKarl the air/fuel ratio can be determined by the oxygen concentration in the exhaust gases as a check for the readings of temperature, maf etc on the inlet side.
    – Solar Mike
    Apr 13, 2020 at 13:16
  • So what would it mean to have a high oxygen concentration vs having a low oxygen concentration?
    – Caleb
    Apr 13, 2020 at 13:19
  • 1
    @DarkNRahlKarl not part of your original question and this is not a chat.
    – Solar Mike
    Apr 13, 2020 at 13:20
  • 1
    @DarkNRahlKarl - If you'd like to chat, you can in The Pitstop. Apr 14, 2020 at 11:37

When you say "cable" are you indicating a copper core wire sheathed with a high-temp insulator material?

The reason I ask is that some manufacturers would run an auxiliary ground strap from the engine to the frame; often being attached on the engine side using one of the exhaust manifold bolts.

They're usually pretty easy to ID as they are often braided wire and are not insulated, running from the engine to the frame, or sometimes into the ground bundle of the wiring harness.

If that's the case then you'd simply need to replace the aux ground when reassembling. BTW, be sure to leave some slack in the connection to allow for engine flexing against the motor mounts under load.

  • 1
    I always gound those flexible straps connected to a bolt or nut on a cooler part of the engine block - as those straps are relatively soft...
    – Solar Mike
    Apr 14, 2020 at 5:50
  • I've updated my question with an image so please check it out.
    – Caleb
    Apr 16, 2020 at 3:31

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