Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
- Verify the integrity of the entire air induction system and verify that none of the following conditions exist:
- Any damaged components
- An air flow restriction
- Any vacuum leak
- Improperly routed vacuum hoses
- A restriction in the MAP Sensor port or the BARO port
- Proper operation of the Positive Crankcase Ventilation (PCV) system
- In cold climates, inspect for any snow or ice buildup at the BARO port on the ECM
- Missing, restricted or leaking exhaust components. Refer to Symptoms - Engine Exhaust .
- Engine mechanical condition; for example: low compression or incorrect timing chain installation. Refer to Symptoms - Engine Mechanical .
- If a condition is found
If a condition is found, repair or replace the component as appropriate.
- If no condition is found
- Ignition OFF, and all vehicle systems OFF. It may take up to 2min for all vehicle systems to power down. Disconnect the harness connector at the B74 Manifold Absolute Pressure Sensor.
- Test for less than 2Ω between the low reference circuit terminal 2 and ground.
- If 2Ω or greater
- Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
- Test for less than 2Ω in the low reference circuit end to end.
- If 2Ω or greater, repair the open/high resistance in the circuit.
- If less than 2Ω, replace the K20 Engine Control Module.
- If less than 2Ω
- Ignition ON.
- Test for 4.8-5.2V between the 5V reference circuit terminal 1 and ground.
- If less than 4.8V
- Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
- Test for infinite resistance between the 5V reference circuit and ground.
- If less than infinite resistance, repair the short to ground on the circuit.
- If infinite resistance
- Test for less than 2Ω in the 5V reference circuit end to end.
- If 2Ω or greater, repair the open/high resistance in the circuit.
- If less than 2Ω, replace the K20 Engine Control Module.
- If greater than 5.2V
NOTE:If the signal circuit is shorted to a voltage the ECM or the MAP Sensor may be damaged.
- Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
- Ignition ON, test for less than 1V between the 5V reference circuit and ground.
- If 1V or greater, repair the short to voltage on the circuit.
- If less than 1V, replace the K20 Engine Control Module.
- If between 4.8-5.2V
- Ignition ON.
- Verify the scan tool MAP Sensor parameter is less than 0.5V.
- If 0.5V or greater
- Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
- Ignition ON,
- Test for less than 1V between the signal circuit terminal 3 and ground.
- If 1V or greater, repair the short to voltage on the circuit.
- If less than 1V, replace the K20 Engine Control Module.
- If less than 0.5V
- Ignition OFF, install a 3A fused jumper wire between the signal circuit terminal 3 and the 5V reference circuit terminal 1.
- Ignition ON.
- Verify the scan tool MAP Sensor voltage parameter is greater than 4.5V.
- If 4.5V or less
- Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
- Remove the jumper wire,
- Test for infinite resistance between the signal circuit terminal 3 and ground.
- If less than infinite resistance, repair the short to ground on the circuit.
- If infinite resistance
- Test for less than 2Ω in the signal circuit end to end.
- If 2Ω or greater, repair the open or high resistance in the circuit.
- If less than 2Ω, replace the K20 Engine Control Module.
- If greater than 4.5V
- Test or replace the B74 Manifold Absolute Pressure Sensor.