I/M Emission Testing on Dynamometer
Date: May 1998Order No.: S-SI-MBNA-14/12A
Supersedes: S-SI-MBNA-14/12, March 1995
Group: 14
Revision: Updated to include model application guide for I/M 240 dynamometer testing
SUBJECT:
ALL MODELS
I/M 240 EMISSION TESTING ON DYNAMOMETER
The enhanced Inspection/Maintenance emission testing program (I/M 240) is in effect in several States.
Please note, the following vehicles may not be tested on a 2-wheel dynamometer:
^ MB vehicles equipped with ASR, ESP, or ETS traction systems will not function on a 2-wheel dynamometer. When only the rear wheels spin, the logic circuit in the traction control module interprets this as "slippage" (similar to accelerating on ice). The traction control module will reduce throttle position, making testing impossible.
Note:
Under no circumstances is the traction system to be disabled or switched off in order to perform the I/M 240 emission test.
^ MB vehicles equipped with 4MATIC will not function on a 2-wheel dynamometer.
All other vehicles up to Model Year 1992 may be tested on a 2-wheel dynamometer.
All vehicles equipped with a traction system, and any vehicle as of Model Year 1993, must be tested on a 4-wheel dynamometer.
According to EPA procedures, if an emission inspector has difficulty in performing the I/M 240 test on a 2-wheel dynamometer, there are two options which can be considered:
^ Test the vehicle on a 4-wheel dynamometer.
or
^ Perform an optional emission test at idle +2800 rpm.
MODEL APPLICATION CHART: DYNAMOMETER USAGE 240 TESTING