Vehicle failed MOT on high emissions (CO off the scale at fast idle..seemingly). Customer changed O2 sensor and asked me to check emissions before he took it for re-test. Emissions now weak at both idle and fast idle. (Readings below at fast idle) CO-0.00 HC- 1ppm CO2 - 12.36 O2 - 4.41 Lambda - 1.25
Using AD I got Fault code P0170 O2 sensor signal low. Confirmed with scope...sensor not switching but stays steady at around 39mv. (engine hot) Will not even switch if I blip throttle. After cat O2 sensor steady at about 214mv
Other readings EGR valve logged as Open EGR feedback - 0.00v EGR position feedback 0%. O2sensor loop open Bank1 sensor 1 - AF ratio = Lean Bank2 sensor 2 - AF ratio = Lean. Short Term Fuel trim = 0%
I thought I would clean/blank off EGR but here is a problem..I can't find one..is it under the Inlet manifold ?.I couldn't look from under the vehicle cos it was standing on wet dolomite but i can't feel one. There is a little device on the side of manifold which i understand is called a Varitract ?.... something I've never noticed before. Exhaust is sound and customer says the car runs well. I can find no air leaks/split pipes. MAF sensor voltage on snap acceleration goes up to about 3.8v.