Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC2011SAVANA SPECIAL 4.8 AREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 4 (ENGINE CONTROLS AND FUEL - 6.6L (LGH) - DTC P0016 THROUGH DTC P11DC)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P0400TESTINGCIRCUIT/SYSTEM TESTING
2011 GMC Savana Special 4.8 A
Circuit/System Testing
2011 GMC Savana Special 4.8 ASECTION Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
NOTE:
- Perform the Circuit System Verification before proceeding with Circuit/System Testing.
- Always replace the EGR valve or EGR cooler gaskets when removal or replacement of the components is necessary.
- Recording of Mass Air Flow parameter g/s are valid only if the Reduced Engine Power message is not present.
- Engine running, perform the following:
- Maintain engine speed at idle.
- With a scan tool, command the EGR solenoid to 0 % and record the MAF Sensor g/s parameter.
- Command the EGR solenoid to 40 % with a scan tool while observing the EGR Position Sensor and the MAF Sensor g/s parameters. Record the MAF Sensor parameter. The difference between the MAF Sensor parameter at 0 % EGR solenoid position and 40 % EGR solenoid position should be greater than 15 g/s.
- If the MAF Sensor parameter is not within the specified range, inspect the EGR cooler and the EGR valve passages for a restriction. If a condition is found, repair or replace the affected component as necessary.
- Ignition OFF, inspect for the following:
- The exhaust system for leaks, restrictions, or for modification of the original equipment manufacture (OEM) part
- A restriction in the air cleaner and the air intake ducts
- A restriction in the turbocharger charge air cooler system
- A restriction in the intake manifold
- If a condition is found, repair or replace the affected component as necessary.
- Test the air induction system for air leaks between the MAF sensor and the turbocharger. Perform the Induction System Smoke Test. Refer to Charge Air Cooler Diagnosis (Full System Air Leak Test) , Charge Air Cooler Diagnosis (Induction System Smoke Test) .
- Test the charge air cooler system for leaks. Perform the Full System Air Leak Test. Refer to Charge Air Cooler Diagnosis (Full System Air Leak Test) , Charge Air Cooler Diagnosis (Induction System Smoke Test) .
- If the exhaust, air induction, charge air cooler and mass air flow systems test normal, Test or replace the Q14 EGR Valve.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.