Hi everyone ! Well, I just replaced the cylinder head on my 95 850 GLT non-turbo wagon. It runs GREAT!! This was my first time diving in, head first, pun intended, to a 5 cyl, DOHC engine! I went to get the car inspected and the NOX level, is .3 over the limit !! Everything else was way below the limits set by the Commonwealth of Massachusetts! I plugged in my OBD II scanner, and got a low voltage message on the bank 1 O2 sensor ?? Both have been replaced! Then I went to the "live data" screen...here's what it said:

fuel sys1 OL, FAULT

fuel sys2 OL, FAULT

What the heck does this mean?? LOL
Thanks in advance for any and all help / suggestions!

Warren

 

Hi Warren,

Glad to hear your 850 is back in business, except the emissions inspections.

Over-limit NOx seems to have been a common problem on 850s. I still don't have a definite solution, but something is allowing the engine to run hotter than it should, or there may be a trivial electronic control input/output that is off the spec.

I have a few questions:

1. When you replaced the O2 sensors, did you replace them with OEM (Bosch)? Many modern cars don't like to be treated with non-OEM parts. In some instances, even Bosch units seem to fail too soon or there have been manufacturing defects (seems to be common on German electronic devices).

2. What brand/model of tester are you using? This is my personal opinion, but either Actron or Snap-on hand-held scanner seems to be the best choice for home mechanics. As to "OL", it probably stands for "Over Load", at least that was the case with Craftsman digital multimeter. But I have no clue as to what those messages refer to.

I'll let other experts help you on this.


JPN

EDIT: Try visiting a local AutoZone or other auto parts shops that provide free OBD-II diagnostic service. Their scanner may be able to give you more accurate definitions.

 

Did you mix the plugs up between o2 sensors.Back is connected to front harness and front is connected to back harness? This would give you your issues. Keep it simple.

 

Hi ! In answer to both replies, first off, yes, they are BOSCH O2 sensors, not the "direct fit", but not the universal cheapies, either! They are 2 different part numbers, specified for the front & rear of my 850. I'll have to look at the scanner to see what brand/model it is. I got it on EBAY! LOL As far as reversing the plugs, unless they were reversed before I bought the car, they are in the same place they were before replacement! Is there a way to tell if they had been reversed? The car runs GREAT! It does have a little "rolling surge" at idle, and the NOX emissions test results were .3 over the allowed limit! I'm running my second large bottle of TECHRON through it now, as per JPN's suggestion on my other post! And I did have the vac lines to the EGR solonoid reversed! The idle smoothed out to just a slight "rolling surge" when I put the lines back where they belonged!
Thanks again, for ALL your help & suggestions!
Warren