new540iowner
02-29-2004, 12:04 PM
Well, after one and a half years of owning my 94 540, I finally figured out
why I was getting this code despite changing the old sensors with new
sensors. My symptoms were a rough idle when cold which worked itself out when warmed up. All intake manifold gaskets (front, rear and 4 bottom) were replaced along with a fuel pressure regulator, new fuel injectors, new ignition coils, new motor mounts and a new idle control valve. After all these items were replaced, I was still getting the 1221 code but couldn't figure out why I was getting 18-21 MPG and the rough running in the morning. So I said to myself, "Let's check the 12V signal to the O2 sensors coming from the relay when the car was started." So I pulled out the voltmeter and didn't get any 12V signal from either O2 sensor. Next step was to open up the E-Box and pull the relay. The relay on my car was underneath in the middle and closest to the passenger side wheel. I probed the "hot" 12V terminal on the relay receptacle and I was indeed getting 12V.
I then proceeded to the stealer for the replacement relay ($15) and reinstalled. Reset the battery and started up. DME now returns a series of 1444 codes which means everything is clear. Hope this helps someone else!
why I was getting this code despite changing the old sensors with new
sensors. My symptoms were a rough idle when cold which worked itself out when warmed up. All intake manifold gaskets (front, rear and 4 bottom) were replaced along with a fuel pressure regulator, new fuel injectors, new ignition coils, new motor mounts and a new idle control valve. After all these items were replaced, I was still getting the 1221 code but couldn't figure out why I was getting 18-21 MPG and the rough running in the morning. So I said to myself, "Let's check the 12V signal to the O2 sensors coming from the relay when the car was started." So I pulled out the voltmeter and didn't get any 12V signal from either O2 sensor. Next step was to open up the E-Box and pull the relay. The relay on my car was underneath in the middle and closest to the passenger side wheel. I probed the "hot" 12V terminal on the relay receptacle and I was indeed getting 12V.
I then proceeded to the stealer for the replacement relay ($15) and reinstalled. Reset the battery and started up. DME now returns a series of 1444 codes which means everything is clear. Hope this helps someone else!