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 -40°F (-40°C), go to next step. If IAT sensor value is not -40°F (-40°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 . Check IAT sensor and harness connector terminals for corrosion or poor connection. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If connector terminals are okay, turn ignition switch to ON position and measure volage between ground and IAT sensor harness connector C31 terminal No. 2 (Light Blue wire). See Fig 1 . If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, check for open circuit or short to power in Light Blue wire between ECM and IAT sensor. Turn ignition switch to LOCK position and check for ECM 26-pin harness connector C51-3 terminals for corrosion or poor connection. ECM is located under instrument panel, behind glove box. See Figure . If Light Blue wire circuit and ECM connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If Light Blue wire circuit and ECM connector terminals are okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
- Connect fused jumper wire between IAT sensor harness connector C31 terminals No. 1 and 2. See Fig 1 . Turn ignition switch to ON position. Using scan tool, observe IAT sensor values. If IAT sensor value is 302°F (150°C), replace IAT sensor. See INTAKE AIR TEMPERATURE (IAT) SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION article. If IAT sensor value is not 302°F (150°C), check for open circuit in Blue/White wire between ECM and IAT sensor. Turn ignition switch to LOCK position and check for ECM 26-pin harness connector C51-3 terminals for corrosion or poor connection. ECM is located under instrument panel, behind glove box. See Figure . If Blue/White wire circuit and ECM connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If Blue/White wire circuit and ECM connector terminals are okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .