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GMC Exhaust Systems

What do the GMC exhaust system warning lights mean? Can a GMC exhaust system fault result in reduced vehicle speed? Why is a GMC exhaust turning red hot? How is the system reset after filling GMC exhaust fluid? Diagnosing and fixing GMC exhaust system problems can be complicated. The guidance and insights of Experts will give vehicle owners the information they need to get the right repairs done.

Read below where Experts have answered a variety of questions pertaining to GMC exhaust systems problems.

What is causing the ‘clean GMC exhaust filter’ and ‘engine power’ warning lights are on in a 2500HD Duramax and can it still be driven?

Once the engine power warning appears, it is an indication that the exhaust filter cleaning process is not happening. The vehicle will need to be serviced by a dealer. If the vehicle is driven in its present condition with a clogged GMC exhaust system, the following will occur:
• The Malfunction Indicator Lamp (MIL) will come on and the warning message will continue to be displayed. A chime will also sound.
• DTC (Diagnostic Trouble Code) P2463 will be set due to the soot buildup in the exhaust system.
• The Engine Power is Reduced message will appear and the vehicle will operate only at reduced power.
• At this point no self-cleaning of the exhaust is possible and dealer service becomes essential.
• Damage may occur to the exhaust system.

What causes a ‘poor exhaust quality’ indicator to appear on a 2500 Denali and the speed is limited to 55 MPH?

In many cases this type of message is the result of one of the Nox sensors in the GMC exhaust system failing. Another cause could be a calibration issue with the computer. There were software issues with some earlier models of this vehicle resulting is false messages appearing. A software update was made available to fix this. Since the GMC exhaust fluid level is okay, it is likely to be a computer glitch which means taking the vehicle to a dealer as the software update can only be done using a GM computer. The Nox sensor should also be checked at that time.

What will cause the GMC exhaust pipe of a 2000 Sonoma to be red hot and prevent the vehicle from going over 20 MPH?

This could be from the engine running too lean, or because of a vacuum leak allowing excess air to enter the engine. Checking the fuel/air mixture and doing a smoke test will determine if either of these is the cause. Also check the catalytic converter, if it has become restricted it can overheat and restrict engine power. An exhaust back pressure test will determine if this is the reason for the problem. Any back pressure reading of 1.5 PSI and above indicates exhaust restriction.

What causes the ‘diesel exhaust fluid warning’ light to appear in a 2011 GMC Duramax even though the exhaust fluid was filled?

First, try a Global Rest, which removes any error messages from the system. To do this, disconnect the negative battery cable from the battery and touch it to the positive cable for a few seconds, then reconnect it. If this does not work, drive the vehicle at over 6 MPH for five minutes to release the warning. If the vehicle speed has been reduced because of the warning, and GMC exhaust fluid has been subsequently added, it can take up to 30 seconds after the engine starts for the warning to clear. If the warning disappears while driving, the vehicle must be brought to a complete stop for the speed restriction to be removed.

Will installing a larger GMC exhaust on a 1995 2500HD Suburban increase power?

Fitting a larger exhaust system should result in a marginal increase in engine power. In this case it could be anything up to 10 HP.

Problems with the GMC exhaust system, if not tackled correctly, can lead to serious engine damage and major repair costs. The best way to avoid this is to get the right information on actions the owners should take. The guidance and answers of Experts are a huge help to drivers facing GMC exhaust system problems.
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