Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, and all vehicle systems OFF, disconnect the harness connector at the B74 manifold absolute pressure sensor. It may take up to 2 minutes for all vehicle systems to power down.
- Test for less than 2 Ω between the low reference circuit terminal A or 2 and ground.
- If 2 Ω or greater
- Ignition OFF, disconnect the X2 harness connector at the K20 engine control module.
- 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 C or 1 and ground.
- If less than 4.8 V
- Ignition OFF, disconnect the X2 harness connector at the K20 engine control module.
- 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
- 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
NOTE:If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.
- Ignition OFF, disconnect the X2 harness connector at the K20 engine control module, 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
- Verify the scan tool MAP voltage parameter is less than 0.2 V.
- If 0.2 V or greater
- Ignition OFF, disconnect the X2 harness connector at the K20 engine control module, ignition ON.
- Test for less than 1 V between the signal circuit terminal B or 3 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 0.2 V
- Install a 3 A fused jumper wire between the signal circuit terminal B or 3 and the 5 V reference circuit terminal C or 1.
- Verify the scan tool MAP voltage parameter is greater than 4.5 V.
- If 4.5 V or less
- Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the K20 engine control module.
- Test for infinite resistance between the signal circuit terminal B or 3 and ground.
- If less than infinite resistance, repair the short to ground on the circuit.
- If infinite resistance
- 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.