P0170 P0173 Error codes Definitive test on AMM
 

2000 C280 with 63m. I have been getting an intermittent CEL that is now on all the time. Error code is P0170 and P0173. Is no power at 4000RPM and WOT a definitive indication that the AMM is kaput? Power seems fine at 4000 rpm and hard acceleration. Tried a spritz of CRC sensor cleaner but light comes back on within 20 miles. Just had a previous code P0150 and changed left front o2 sensor. Just changed plugs and wires to cure a rough idle. And I am due for a fuel filter change.

glenmore
2000 C280
1991 300CE
1990 LS400

The definitive test would evaluate fuel trims data or viewing calc load on OBDII during the event.

But since I buy them by the bushel I'd just throw one at it and view the results to save a step.

Steve, are you saying to look at the calc load "snapshot" data stored when the code happened? What do you look for?

No, I'm saying to look at the calculated load pid when the engine falls on its face at 4000+rpm full throttle.

Calculated load should be over 80% in such conditions. Calc load is calculated from AMM output. If the output calculates to 40-60% then it obviously is under reporting such a condition.

http://www.picoauto.com/automotive-oscilloscope-guide/lambda-sensors.html

One of my favorite videos... guy is articulate , too.

change your MAF

So far so good. Replaced the AMM insert and no CEL so far. After cleaning and clearing the codes last time, the CEL came back on after a day or so.

Thanks all,

glenmore
2000 C280
1991 300CE
1990 LS400