Diagnosis & Repair Procedure

NOTE: For better performance and results of this diagnostic procedure, usage of appropriate wiring diagram is recommended. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

NOTE: Perform all voltage and resistance tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use an ohmmeter to isolate wiring harness shorts or opens.

If engine system check has been performed, go to next step. If engine system check has not been performed, perform A-4: ENGINE SYSTEM CHECK under SYSTEM TESTS, then go to next step.
Turn ignition switch to ON position. Using scan tool, observe IAT sensor values. If IAT sensor value is 302°F (150°C), go to next step. If IAT sensor value is not 302°F (150°C), problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. After repair, repeat DTC CONFIRMATION TEST .
Turn ignition switch to LOCK position. Disconnect IAT sensor 2-pin harness connector C31, located on air cleaner box. See Figure . Turn ignition switch to ON position. Using scan tool, observe IAT sensor temperature values. If scan tool display is -40°F (-40°C), replace IAT sensor. See INTAKE AIR TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION article. If scan tool display is not -40°F (-40°C), check for short to ground in Light Blue wire between ECM and IAT sensor. If short to ground is found, repair as necessary and repeat DTC CONFIRMATION TEST . If short to ground is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .