Diagnostic Aids

Perform this test only when directed here. This system test is intended to diagnose.

• Intake Air Temperature 2 (IAT2) Sensor
• IAT2 & SIG RTN Harness Circuits
• Powertrain Control Module (PCM)

NOTE: Test procedure begins with step 10). No test procedures have been omitted.
1. 10) DTC P1115: Induce Opposite Signal To PCM
   With IAT2 sensor disconnected, connect jumper wire between IAT2 sensor harness connector terminals. Turn ignition switch to ON position. Using scan tool, select IAC2 PID from PID/DATA MONITOR & RECORD menu. If a communication link error is displayed, remove jumper wire and go to step  12). If PID voltage is less than .2 volt, replace IAT2 sensor. If PID voltage is .2 volt or more, turn ignition switch to OFF position, remove jumper wire and go to next step.
2. 11) Check IAT2 Sensor Signal & SIG RTN Circuits For Open
   
   Turn ignition switch to OFF position. Disconnect PCM connector(s). Measure resistance of IAT2 sensor signal circuit between PCM connector terminal No. 38 and IAT2 sensor. Measure resistance of IAT2 sensor SIG RTN circuit between PCM connector terminal No. 91 and IAT2 sensor. See Fig 1. If all resistance readings are less than 5 ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION (VID) BLOCK PROCEDURE . If any resistance reading is 5 ohms or more, repair open circuit.
3. 12) Check IAT2 Sensor Signal Circuit For Short To VREF
   
   Turn ignition switch to OFF position. Disconnect PCM connector(s). Measure resistance between IAT2 sensor signal and VREF circuit at PCM connector terminals No. 38 and 90. If resistance is more than 10 k/ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION (VID) BLOCK PROCEDURE . If resistance is 10 k/ohms or less, repair short to VREF.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.
4. 20) DTC P1114: Induce Opposite Signal To PCM
   
   Disconnect IAT2 sensor connector. Turn ignition switch to ON position. Using scan tool, select IAC2 PID from PID/DATA MONITOR & RECORD menu. If PID voltage is more than 4.2 volts, replace IAT2 sensor. If PID voltage is 4.2 volts or less, turn ignition switch to OFF position, go to next step.
5. 21) Check VREF Voltage To TP Sensor
   
   Turn ignition switch to OFF position. Disconnect TP sensor connector. Turn ignition switch to ON position. Measure voltage between VREF and SIG RTN terminals at TP sensor harness connector. See Fig 2. If voltage is 4-6 volts, VREF voltage is sufficient, reconnect TP sensor connector and go to next step. If voltage is not 4-6 volts, go to TEST C .
6. 22) Check IAT2 Sensor Signal Circuit For Short To Ground
   
   Turn ignition switch to OFF position. Disconnect PCM connector(s). Measure resistance between PCM connector terminals No. 38 and 91. Measure resistance between PCM connector terminal No. 38 and ground. If all resistance readings are more than 10 k/ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION (VID) BLOCK PROCEDURE . If any resistance reading is 10 k/ohms or less, repair short circuit.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 30). No test procedures have been omitted.
7. 30) DTC P0127: IAT2 Too High - Check Supercharger Intercooler Pump Operation
   
   Turn ignition switch to OFF position. Connect scan tool to DLC. Turn ignition switch to ON position. Using scan tool, select Output Test Mode. Select Mode: ALL ON. Command pump to run. If supercharger intercooler pump runs, go to next step. If supercharger intercooler pump does not run, go to TEST KP .
8. 31) Check Intercooler System
   
   Make the following visual inspections:
   • Intercooler Fluid Level
   • Check For Cracked Coolant Lines
   • Check For Blocked Heat Exchanger Or Coolant Lines
   • Check For Crossed Coolant Lines

   Repair as necessary. If intercooler system is okay, go to next step.

9. 32) Simulate High IAT2 Voltage Signal
   
   Turn ignition switch to ON position. Using scan tool, select IAT2 V PID. Monitor PID voltage while disconnecting IAT2 sensor connector. If PID voltage is more than 4 volts, go to next step. If PID voltage is 4 volts or less, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION (VID) BLOCK PROCEDURE .
10. 33) Simulate Low IAT2 Voltage Signal
    
    Ensure ignition switch is turned to ON position. Monitor IAT2 PID voltage while connecting jumper wire between IAT2 sensor harness connector IAT2 signal and SIG RTN terminals. If IAT2 PID voltage is one volt or more, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION (VID) BLOCK PROCEDURE . If IAT2 PID voltage is less than one volt, reconnect IAT2 sensor and go to appropriate PIN VOLTAGE/PID VALUE - INPUTS table in PIN VOLTAGE/PID VALUE CHARTS - TRUCKS article. Compare PID values from road test conditions for IAT2 with values in PIN VOLTAGE/PID VALUE - INPUTS table. If IAT2 sensor is not within range, replace IAT2 sensor.
    Fig 1: Identifying IAT2 Sensor Circuits & Connector Terminals

    Courtesy of FORD MOTOR CO.
    Fig 2: Identifying TP Sensor Circuits & Connector Terminals (F150 Lightning 5.4L SC Pickup)

    Courtesy of FORD MOTOR CO.