Circuit/System Testing

NOTE:

All electrical components and accessories must be turned OFF and allowed to power down.

Verify none of the following conditions exist:
- Loose clamps, cracks, or other damage in the air intake duct system
- Splits, kinks or improper connections at the vacuum hoses
- Vacuum leaks at the intake manifold and throttle body
- A dirty, restricted, or deteriorating air filter element
- A leaking, loose, disconnected, or cracked positive crankcase ventilation (PCV) valve, pipe, or seal
- A collapsed, restricted, or collapsed air intake duct
- A misaligned or damaged air intake duct
- 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
- Any intake manifold leak
- A MAP Sensor seal that is leaking, missing, or damaged
- An Intake Manifold Resonator with a leaking seal, or a cracked or broken housing
- Missing, restricted or leaking exhaust components - Refer to Symptoms - Engine Exhaust .
- If a condition exists
  Repair or replace component as appropriate.
- If no condition exists
Ignition OFF, and all vehicle systems OFF. It may take up to 2 min for all vehicle systems to power down. Disconnect the harness connector at the B74 Manifold Absolute Pressure Sensor.
Test for less than 2 Ω between the low reference circuit terminal 2 or C and ground.
- If 2 Ω or greater
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
  - If 2 Ω or greater, repair the open/high resistance in the circuit.
  - If less than 2 Ω, replace the K20 Engine Control Module.
- If less than 2 Ω
Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 1 or A and ground.
- If less than 4.8 V
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
  - If less than infinite resistance, repair the short to ground on the circuit.
  - If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
  - If 2 Ω or greater, repair the open/high resistance in the circuit.
  - If less than 2 Ω, replace the K20 Engine Control Module.
- If greater than 5.2 V
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Ignition ON, test for less than 1 V between the 5 V reference circuit and ground.
  - If 1 V or greater, repair the short to voltage on the circuit.
  - If less than 1 V, replace the K20 Engine Control Module.
- If between 4.8-5.2 V
Ignition ON, verify the scan tool MAP Sensor parameter is less than 0.5 V.
- If 0.5 V or greater
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Ignition ON, test for less than 1 V between the signal circuit terminal 3 or B and ground.
  - If 1 V or greater, repair the short to voltage on the circuit.
  - If less than 1 V, replace the K20 Engine Control Module.
- If less than 0.5 V
Ignition OFF, install a 3 A fused jumper wire between the signal circuit terminal 3 or B and the 5 V reference circuit terminal 1 or A.
Ignition ON, verify the scan tool MAP Sensor voltage parameter is greater than 4.5 V.
- If 4.5 V or less
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Remove the jumper wire, test for infinite resistance between the signal circuit terminal 3 or B and ground.
  - If less than infinite resistance, repair the short to ground on the circuit.
  - If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
  - If 2 Ω or greater, repair the open or high resistance in the circuit.
  - If less than 2 Ω, replace the K20 Engine Control Module.
- If greater than 4.5 V
Test or replace the B74 Manifold Absolute Pressure Sensor.