Diagnostic Aids

Perform this test only when directed by QUICK TEST or other test.

This test is intended to diagnose the following components and circuits:

• Mass Airflow (MAF) sensor.
• Harness circuits: MAF, VPWR and MAF REF.

1. 1) DTC P0100: Check MAF Signal TO PCM
   
   DTC P0100 indicates a malfunction in the MAF sensor circuit. Possible causes are as follows:
   • Faulty MAF sensor.
   • Open or short in harness.
   • Poor harness connection.
   • Air intake leak.
   • Faulty PCM.

   Turn ignition off. Check air intake system for leaks. Connect New Generation Star (NGS) tester to DLC. Start engine and let idle (engine warm). Using NGS tester, access MAF PID. If MAF PID reads 1.0-1.7 volts, go to step  30). If MAF PID reads one volt or less, go to step  10). If MAF PID reads greater than 1.7 volts, go to step  20).

   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 1)  to step 10)  . No test procedures have been omitted.
2. 10) Check VPWR At MAF
   
   Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on. Measure voltage between VPWR circuit at MAF sensor harness connector and ground. See Fig 1. If voltage is greater than 10 volts, go to next step. If voltage is not greater than 10 volts, go to TEST B .
   Fig 1: Identifying MAF Sensor Circuit & Harness Connector Terminals

   Courtesy of FORD MOTOR CO.
3. 11) Check MAF Circuit Short To Ground
   
   Turn ignition off. Disconnect PCM harness connector. Measure resistance between MAF, MAF REF and GND circuits at PCM harness connector. See CIRCUIT PIN IDENTIFICATION  table. If resistance readings are greater than 10 k/ohms, go to next step. If any resistance readings are not greater than 10 k/ohms, repair short in affected circuit.
4. 12) Check MAF Sensor Harness
   
   Disconnect MAF sensor connector. Measure resistance of MAF and MAF REF circuits between MAF sensor harness connector and PCM harness connector. If both resistance readings are less than 5 ohms, go to next step. If either resistance reading is not less than 5 ohms, repair open affected circuit(s).
5. 13) Check PCM
   
   Reconnect PCM harness connector. Start and operate engine at idle. Using NGS tester, access MAF PID at idle and at 2000 RPM. If voltage reading is less than one volt, replace PCM. If voltage reading is not less than one volt, replace MAF sensor.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 13)  to step 20)  . No test procedures have been omitted.
6. 20) Check MAF Circuit For Short To Power
   
   Turn ignition off. Disconnect PCM and MAF sensor harness connectors. Measure resistance between MAF, MAF REF and VPWR circuits. See Fig 1. If resistance measurements are greater than 10 k/ohms, replace MAF sensor. If any resistance measurement is not greater than 10 k/ohms, repair short in affected circuit.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step  20) to step  30). No test procedures have been omitted.
7. 30) MAF Sensor Performance Test
   
   Turn ignition off. Using NGS tester, access MAF PID. Start and operate engine to specified speeds. See MAF SENSOR PERFORMANCE  table. If MAF PID values do not agree with values in table, replace MAF sensor. If MAF PID values agree with table, fault may be intermittent. See TEST Z  or TROUBLE SHOOTING - NO CODES - VILLAGER article.