I had the other day Navara which came in for engine light on. I have plugin the scanner and got the fault code P1051 A/F Sen1 HTR b2. This fault indicates the heater of the sensor is faulty. Before I decide to buy a new one I have checked the wire integrity. Because if you don’t do that you might end up just as a part changer. Look at the following images – which are screenshots from the scanner.
See the bottom part of the image A/F Sens (B)1 and (B2), (B1) the blue line is going down and up as I was revving the engine (WOT), the yellow line should do the same but was just running a straight line. The top part of the image is graphed about modulation power to the heaters of the two sensors. The top right (B2) is at 100% and the line is straight. The power to (B1) is at 94% and the line is synchronized with the graph just below it for the voltages. This indicates that there is something wrong with the heater of (B2).
Now, look at the next images after I have replaced the sensor.
Look at the graphs at the bottom especially (B2) sensor, the yellow line is now moving up and down as the graph of (B1) sensor 1. See the top of this image and both modulation power is at 100% and the lines correspond with each other. Now, this looks better. I have cleared all codes and took the car for a test drive and the fault does not come back. Hope this helps