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.
Circuit/System Testing
2009 Chevrolet Tahoe Base, 4.8 CSECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2010 GMC Yukon XL, 2010 GMC Yukon, 2010 Chevrolet Tahoe, 2010 Chevrolet Suburban, and 2010 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
All electrical components and accessories must be turned OFF and allowed to power down.
- Verify the integrity of the air induction system by inspecting for the following conditions:
- Any damaged components
- Loose or improper installation
- Improperly routed vacuum hoses
- Any vacuum leak
- Any type of restriction
- MAP sensor seal that is missing or damaged
- Verify that restrictions do not exist in the MAP sensor vacuum source.
- Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust .
- Ignition OFF, disconnect the MAP harness connector at the MAP sensor.
- Ignition OFF for 90 s, test for less than 5 Ξ© between the low reference circuit terminal A and ground.
- If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal C and ground.
- If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
- If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Verify the scan tool MAP Sensor parameter is less than 12 kPa.
- If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Install a 3 A fused jumper wire between the signal circuit terminal B and the 5 V reference circuit terminal C. Verify the scan tool MAP Sensor parameter is greater than 103 kPa.
- If less than the specified range, test the signal circuit terminal B for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, test or replace the MAP sensor.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.