For a complete wiring diagram Refer to Section 8WWhen Monitored:With the ignition on.Set Condition:The ECM detects that the (K157) Mass Air Flow Sensor Signal circuit is not within a valid range.Possible CausesINTERMITTENT DTC(K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE(K957) MASS AIR FLOW SENSOR GROUND CIRCUIT SHORTED TO VOLTAGE(F344) FUSED ASD RELAY OUTPUT CIRCUIT OPEN OR HIGH RESISTANCE(K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE(K957) MASS AIR FLOW SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE(K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO GROUND(K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO THE (K957) MASS AIR FLOW SENSOR GROUND CIRCUITMASS AIR FLOW SENSORENGINE CONTROL MODULE (ECM)Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)1. DTC IS ACTIVEIf any Sensor Reference or Sensor Supply voltage DTCs are present, perform the applicable diagnostic procedure before continuing with this test.Ignition on, engine not running.With the scan tool, Clear DTCs in the Engine Control Module (ECM).Start the engine and allow it to reach normal operating temperature.With the scan tool, select View DTCs.Is the status Active for this DTC?YesGo To 2 NoRefer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)2. (K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.Disconnect the Mass Air Flow Sensor harness connector.Turn the ignition on.Measure the voltage of the (K157) Mass Air Flow Sensor Signal circuit in the Mass Air Flow Sensor harness connector.Is there any voltage present?YesRepair the (K157) Mass Air Flow Sensor Signal circuit for a short to voltage. Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo to 33. (K957) MASS AIR FLOW SENSOR GROUND CIRCUIT SHORTED TO VOLTAGE

Measure the voltage of the (K957) Mass Air Flow Sensor Ground circuit in the Mass Air Flow Sensor harness connector.Is there any voltage present?YesRepair the (K957) Mass Air Flow Sensor Ground circuit for a short to voltage. Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo to 44. (F344) FUSED ASD RELAY OUTPUT CIRCUIT OPEN OR HIGH RESISTANCE

Using a 12 volt test light connected to ground, check the (F344) Fused ASD Relay Output circuit in the Mass Air Flow Sensor harness connector.The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.Is the test light illuminated and bright?YesGo to 5NoRepair the (F344) Fused ASD Relay Output circuit for an open circuit or high resistance.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)5. (K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE

Turn the ignition off.Disconnect the ECM harness connector.Measure the resistance of the (K157) Mass Air Flow Sensor Signal circuit between the Mass Air Flow Sensor harness connector and the Engine Control Module (ECM) harness connector.Is the resistance below 10.0 ohms?YesGo to 6NoRepair the (K157) Mass Air Flow Sensor Signal circuit for an open circuit or high resistance.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)6. (K957) MASS AIR FLOW SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (K957) Mass Air Flow Sensor Ground circuit between the Mass Air Flow Sensor harness connector and the Engine Control Module (ECM) harness connector.Is the resistance below 10.0 ohms?YesGo to 7NoRepair the (K957) Mass Air Flow Sensor Ground circuit for an open circuit or high resistance.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)7. (K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO GROUND

Measure the resistance between ground and the (K157) Mass Air Flow Sensor Signal circuit in the Mass Air Flow Sensor harness connector.Is the resistance above 1000 ohms?YesGo to 8NoRepair the (K157) Mass Air Flow Sensor Signal circuit for a short to ground.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)8. (K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO THE (K957) MASS AIR FLOW SENSOR GROUND CIRCUIT

Measure the resistance between the (K157) Mass Air Flow Sensor Signal circuit and the (K957) Mass Air Flow Sensor Ground circuit in the Mass Air Flow Sensor harness connector.Is the resistance above 1000 ohms?YesGo to 9NoRepair the (K157) Mass Air Flow Sensor Signal circuit for a short to the (K957) Mass Air Flow Sensor Ground circuit.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)9. MASS AIR FLOW SENSORConnect the Engine Control Module (ECM) harness connector.Replace the Mass Air Flow Sensor in accordance with the Service Information.Turn the ignition on.With the scan tool, Clear DTCs.Start the engine and allow it to reach normal operating temperature.With the scan tool, select View DTCs.Is the status Active for this DTC?YesGo to 10NoTest Complete.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)10. ENGINE CONTROL MODULE (ECM)Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Mass Air Flow Sensor and the Engine Control Module (ECM).Look for any chafed, pierced, pinched, or partially broken wires.Look for broken, bent, pushed out or corroded terminals.Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.Look for the data to change or for the DTC to reset during the wiggle test.Refer to any Technical Service Bulletins that may apply.Were any problems found?YesRepair as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace the Engine Control Module (ECM) in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)