Post by
VStar650CL »
https://forums.nicoclub.com/vstar650cl-u299034.html
Sat Jul 16, 2022 9:14 pm
I think you need to take a look at the actual B1S1 voltages instead of what the ECM thinks it's seeing by scanning the alpha. The sudden jump to full rich indicates the sensor is jumping way lean, and that sounds like a wire flexing under engine load when you accelerate. The ECM will only throw a hard code like P014C or P015A if the sensor flatlines or goes non-responsive, but it will pretty much scratch its electronic head over a signal that jumps around without staying flat. I doubt the heater is the problem because it wouldn't cause an instantaneous response, so the Brown wire can be pretty much excluded. The sensor itself is a 2.2V wideband type where lower than 2.2 indicates rich, higher indicates lean. The first thing to exclude (because it's easy) is the sensor ground. Backprobe the White wire on pin 1 (there are two White wires) on the sensor side of the connector with a T-pin or safety pin and jumper it to a good ground, preferably the negative battery post. If the problem goes away, there's high resistance or a break someplace in the circuit between the sensor and ECM pin 15. If that doesn't affect it, you'll need to run a long jumper inside the car so you can watch voltages while causing the problem. Check the White wire on pin 3 first, that's the reference voltage from the ECM and should read 1.8V at all times. If it changes when the problem occurs then there's a problem in that wire between the sensor and ECM pin 66. If that checks out, then there's probably an issue with the Black wire carrying sensor signal to ECM pin 67.