Originally posted by Bob Blaylock:
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I guess I should mention that the P0402 code only ever occurred when the car was stationary and idling, while the codes related to the O2 sensor and to the mixture being lean have only occurred while the car is in motion.
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FWIW, this article may shed some light, or further confuse the issue:
EGR system may be cause of engine warning light My question: was the car idling at 2000 RPM when P0402 came on? Mine idles at about 650 RPMs. This article suggests that the fault, if it is EGR related, would have occurred at higher engine speed, 2000 RPMs or above?
