Circuit/System Testing
WARNING: This page is about a different car, the 2007 GMC Sierra, 2007 GMC Cab & Chassis Sierra, 2007 Chevrolet Silverado, and 2007 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
- You must perform the Circuit/System Verification before proceeding with the circuit/system testing.
- You must perform the Repair Verification after completing the Circuit/System Testing.
- Verify the integrity of the entire air induction system by inspecting for the following conditions:
- A loose or disconnected charge air cooler hose or pipe
- A restricted or collapsed air intake duct
- A misaligned or damaged air intake duct
- A dirty or deteriorating air filter element
- Any objects blocking the air inlet probe of the MAF/IAT sensor
- Any contamination or debris on the sensing elements in the probe of the MAF/IAT sensor
- A cracked or damaged MAF sensor housing
- Any water intrusion in the induction system
- Any snow or ice build-up at the air cleaner, MAF or MAP sensors in cold climates
- An intake manifold leak
- A MAP sensor seal that is missing or damaged
- An Intake Manifold Resonator with a leaking seal, or a cracked or broken housing
- Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
- Ignition OFF for 90 seconds, test for less than 5 ohms of resistance between the MAF low reference circuit terminal 2 and ground.
- If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition OFF, test for less than 5 ohms of resistance between the IAT sensor low reference circuit terminal 4 and ground.
- If greater than the specified range, test the IAT sensor low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 3 and ground.
- If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
- Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 1 and ground.
- If less than the specified range, test the MAF signal 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 MAF signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Test the charge air cooler system for leaks. Refer to Charge Air Cooler Diagnosis (Charge Air Cooler Air Leak Test) or Charge Air Cooler Diagnosis (Full System Air Leak Test) .
- Remove the Intake Manifold Tube. Refer to Intake Manifold Tube Replacement .
- Visually inspect the EGR valve and verify the valve is in the closed position.
- If the EGR valve is not in the closed position, replace the EGR valve.
- Ignition OFF, connect the red lead of the J 38522 to the signal circuit terminal A at the MAF/IAT sensor harness connector. Connect the battery voltage supply to B+, and ground the black lead.
- Set the J 38522 signal circuit to 5 volts, the frequency to 5K, and the Duty Cycle to Normal.
- Engine idling, observe the scan tool MAP Sensor parameter. The scan tool MAF Sensor parameter should be between 4.950-5.025 Hz.
- If the MAF Sensor parameter is not within the specified range, replace the ECM.