It really depends on what's wrong. There is one sensor package that fits into the plumbing off the nearside of the cylinder head, but it contains two separate sensors, one just for the dashboard gauge and the other feeding the ECU and thus all the other onboard systems (climate control etc). The sensor connection has four ways, two for each of the sensors. Basically the dash gauge is analog, reading the change in resistance of the sensor directly, and the ECU feed is digitised either in the sensor or at the ECU.
What it boils down to is that the ECU does not see the same signal that the dashboard gauge sees, so the dial reading is not helpful in this respect. It could be that your ECU sensor is also borked, which will affect the fuelling. I'd expect that to bring up the CEL though.