I haven't a clue where it might be on that engine. On the ML, it was in the back of the intake manifold, but it has a V6. I think yours has an L6.

You can also try other national chains like AutoZone. They pulled the codes on my 91.

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Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport