07 S550. Codes P2237 and P2240
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Junior Member
Joined: Nov 2019
Posts: 19
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From: SC
07 S550, 99 Q45t, 89 Mirage Turbo
07 S550. Codes P2237 and P2240
07 S550, 133k miles. Started the car one morning and it had the CEL on. Figured I would scan it at work. It is seven miles to work, by the time I got there it ran like crap, smoked, smelt horrible and was having trouble with power delivery and idling. Scanned it and got only those two codes for bank 1 and 2 upsteam o2 sensors (P2237 & P2240). So I figure it was running a fail safe fuel map that is quite rich due to not knowing what the A/F's are. My question is, it seems odd that both o2's failed at the same time. The day before it ran fine. I thought I had read that the ECU can fail in a way that can cause such a condition but only found one reference to it. I also don't have access to decent scan tool to see the voltage of the upsteam o2's (I am assuming they are on the CAN-BUS). Has anyone ran into this before? I'm going to go ahead and do both upstream o2's anyway but it's just the fact they both supposedly died at the same time seems quite odd to me.
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Joined: Mar 2019
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E350 4matic
07 S550, 133k miles. Started the car one morning and it had the CEL on. Figured I would scan it at work. It is seven miles to work, by the time I got there it ran like crap, smoked, smelt horrible and was having trouble with power delivery and idling. Scanned it and got only those two codes for bank 1 and 2 upsteam o2 sensors (P2237 & P2240). So I figure it was running a fail safe fuel map that is quite rich due to not knowing what the A/F's are. My question is, it seems odd that both o2's failed at the same time. The day before it ran fine. I thought I had read that the ECU can fail in a way that can cause such a condition but only found one reference to it. I also don't have access to decent scan tool to see the voltage of the upsteam o2's (I am assuming they are on the CAN-BUS). Has anyone ran into this before? I'm going to go ahead and do both upstream o2's anyway but it's just the fact they both supposedly died at the same time seems quite odd to me.
Thread Starter
Junior Member
Joined: Nov 2019
Posts: 19
Likes: 9
From: SC
07 S550, 99 Q45t, 89 Mirage Turbo
So in my case it turned out to be a dead Lin-Bus network with the ECM. Pulled it out and sent it to PresserTech in Atlanta Georgia. They tested it and found the processor had failed and required a full replacement (processor can not be replaced, only the drivers can). They stripped all the info off my old ECM and put it on a refurbished unit at the cost of about $1,000 (plug and play with no programing needed on my end). I then replaced both up stream O2's and all spark plugs as the overly rich running condition had fouled both items. Problem solved.
If you have access to a good scanner, you could check the long and short term fuel trims. See if it is running overly rich. I was at +30%. Or if you have a scope you can disconnect your upstream O2's (remove the questionable items to see if they are dragging down the network) and probe one of the wires for the alternator (I forgot which one) and see if you have a square wave, if not more than likely it is a Lin-Bus issue.
I'm not going to say that is your issue, but it is what needed to be done for myself.
If you have access to a good scanner, you could check the long and short term fuel trims. See if it is running overly rich. I was at +30%. Or if you have a scope you can disconnect your upstream O2's (remove the questionable items to see if they are dragging down the network) and probe one of the wires for the alternator (I forgot which one) and see if you have a square wave, if not more than likely it is a Lin-Bus issue.
I'm not going to say that is your issue, but it is what needed to be done for myself.
