Went and bought Michells manual for the vehicle so that I could trace the wiring. There are no problems with the wiring. With the engine running the signal wire of the MAS should have between 0.7 and 1.1 volts; it has 0.23 - 0.25 volts. Not sure of what the relationship of voltage to richness of F/M is but the vehicle is running rich by the smell of the exhaust. Because of the low voltage readings I called the MAS defective and am getting another replacement in 3 days. Called a Nissan repair shop and they stated that they have seen this problem with a defective and/or after market MAS. I question the after market part because it sounds like a sales pitch. If a new MAS fails to cure the problem, I will build a consult cable and use Blazt Nissan data scan to further diagnose the problem. I have been manually reseting the computer after each test and manually setting the diagnostic scan from the computer. Even when I disconnect something like the TPS the computer only shows an error code 12. I wonder why? A defective ECM is a possibility, but per the dealer, a rare one.
The problem of building and using a consult cable is that I then will want to tinker with the ECM to change the performance to what I want. Because I am good with both computers and electronics this would not be the best option for me.
When I get the new new MAS, I will get back with you. In the mean time: what is your experience with the failure of ECM's; rare or common? Do you know of a quick test I could perform to determine if the ECM has failed and is pulling the MAS signal voltage down? And finally, in this model/year of car, do you know what the relationship between fuel/air/injector timing is to MAS signal level? The reason for this last question is because I used a battery and potentiometer to apply 1.0 volts to the MAS signal line and the car stalled.
Friday, July 27th, 2007 AT 6:46 PM