Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to all 2000 - 2019 models with gasoline engines.

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  All All 2000 - 2019 All All All (Gasoline Engines Only) All

• The SES light is on, and initial diagnosis may show fuel trim and/or O2 sensor related codes such as P0171, P0174, P0420 and P0430.

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  A customer may comment the vehicle has an SES light on. Initial diagnosis may display any of these fuel trim and/or O2 sensor related codes, P0101, P0137, P0138, P0140, P0141,P0157, P0158, P0160, P0161, P0171, P0174, P0420, P0430, P1174, P1175, P2096, P2097, P2098, P2099, P2177, P2178, P2179, P2180, P2187, P2188, P2189, P2190. P2270, P2271, P2272, P2273.

Steps to confirm (in the document’s order)

1. If normal SI diagnostics do not resolve it and an intake vacuum leak or exhaust leak is suspected, the J41413-200 Evaporative System Tester smoke machine, the J-41416 ultrasonic leak tester, or soapy water with low pressure air into the tailpipe may help find the leak.

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   If normal SI diagnostics does not lead to a resolution and an intake vacuum leak or an exhaust leak is suspected, the use of the J41413-200 Evaporative System Tester smoke machine or the J-41416 ultrasonic leak tester, or possibly using soapy water and low pressure air into the tailpipe may be useful to find the leak.

2. For an intake leak, the smoke can be introduced into the brake booster hose or the oil dipstick tube.

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   For an intake leak the smoke can be introduce into the brake booster hose or the oil dipstick tube.

3. Soapy water can be sprayed near the gasket and seams and on all vacuum nipples.

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   Soapy water can be sprayed near the gasket and seams and all vacuum nipples.

4. For an exhaust leak, a hose into the tailpipe carrying smoke or air, sealed with shop towels, is effective.

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   For an exhaust leak the hose into the tailpipe, with smoke or air, sealed with shop towels proves to be effective.

5. Then spray soapy water around the seals, seams and bosses.

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   Then soapy water would be sprayed around seal, seems and bosses.

6. These methods are very good for finding small leaks around the O2 sensor bosses and slight cracks in an intake plenum or gasket.

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   These methods are very good for finding small leaks around the O2 sensor embossments and slight cracks in an intake plenum or gasket.

Caution

• All of these tests are much more effective if the throttle body is covered/sealed.

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  NOTE: All of these tests are much more effective if the throttle body is covered/sealed.