Oxygen sensor alternative
 

Question,has anyone found a cheaper alternative to the NGK 25620 sensor?

there are numerous stories on the forum about non OEM sensors of every type failing to meet expectations. From outright failure up to intermittent issues are associated with using sensors from other manufacturers. The common theme running thru all these stories is that the owners wished they had just paid a few more dollars and bought the OEM Jaguar part.

Z

Generally speaking, you need to make sure you get the right type of sensor first. The upstream sensors are wide-band, whereas the downstream sensors are narrow-band. The control circuit to get a measurement is completely different, so they cannot be used interchangeably. O2 sensors are very heavily monitored by the ECU for obvious emissions purposes, so a bad part should be detected pretty quickly. There are many ways to shop for parts, but I have had good luck with a "web 2.0" approach, i.e getting cheap parts off of eBay, and rely of the feedback mechanism for protection. The idea is that a vendor with 20,000+ feedback, 99+% positive will likely not want to blow their feedback on quick sales of a bunch of junk parts. More to your question, I have had good luck with DENSO O2 sensors. As usual, there are many brands, but likely much fewer actual manufacturers. To my knowledge, sensors are all "the same", except for the electrical connector. Should be around $50 each, give or take.

Best of luck, keep us posted.