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Cascade Fault Code: •
Affected Models: Mercedes-Benz •
Merc slk 170.449 2.3 petrol
p2036 secondary air inject, malfunction
The secondary air injection pumps air directly into the exhaust in order for the cataltic converter to get upto tempreture more quickly, this works as on cold start there is a rich condition (excess fuel) so therefore adding extra air the catatic coverter gets upto operating tempreture quicker.
On this particlar model for the first approx 110 seconds of cold start the ecu sets the secondary throttle body into closed position (normal tickover warm running it is half open) the ecu sends 12volts to the vacume solinoid valve which in turn opens the breather valve which in turn forces the one way valve open allowing intake air (supplied from the compresser) directly into the exhaust.
on cold start you should see a drop in the pre cat lambda sensor indicating the system is working you can also manually operate the vacume valve and see the drop on the lambda probe
As we can see on the follow two images of the first the o2 sensor voltage is ranging up and down from cold start but what we should see is more like the second picture whereby o2 sensor voltage stays low until the correctamount of time has passed after which we can see lambda control turns on and the valve shuts and the lambda senso strats to control the emmissions
It was found the electric servo valve had power but wasent operating allowing vacume to be transfered to the vacume valve. circuled in red in the below picture
Published • 2021-03-28 10:00:19 • 0 Comments
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