Exhaust Odor in Cabin or Engine Compartment

An exhaust odor in the cabin or in the engine compartment may be noticed on some 2020-2021 Silverado and Sierra models and 2021 Tahoe, Suburban, Yukon, and Escalade models, equipped with the 3.0L diesel engine (RPO LM2). The exhaust odor may be caused by an improper weld on the exhaust backpressure valve. (Fig. 21)


Fig. 21


If an exhaust odor is present, test for a leaking exhaust backpressure valve weld joint using the GE-52250 Power Smoke Diagnostic Leak Detector or soapy water. Refer to the latest version of #PIP5684 for more information on using the GE-52250 detector.

The exhaust backpressure valve is located between the downpipe from the Selective Catalyst Reduction (SCR) with filter and the underfloor SCR.

Smoke from the GE-52250 detector may not get through the Diesel Particulate Filter (DPF), so test downstream in the exhaust system by administering the smoke at the fitting on the tailpipe bladder seal. The tailpipe bladder seal does not reach the exhaust cooler, so it will be necessary to wrap duct tape around the tailpipe to seal the cooler holes. Be sure to remove the duct tape from the exhaust cooler after completing testing.

Repair any leaks identified after testing the exhaust system components. An ineffective weld at the flange joint may be a source of a leak. (Fig. 22) If the weld joint is leaking, replace the exhaust backpressure valve.


Fig. 22


– Thanks to Robert Bastien

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