AboutCAJUNSC/RAMBLER390 Expertise 1998 and NEWER questions ONLY!! I WILL REJECT QUESTIONS FROM 1998 BACK. Electrical diagnosis. Brake Diagnosis. Driveability, Service Engine Soon Lights. Some Engine mechanical. Tires and wheels. ABS. HVAC. Air Bag (SIR). Interior, seats, etc... 6.6L Duramax Diesel diagnosis. 6.5L diesel diagnosis. I WILL not answer Alignment questions OR carburetor questions. No heavy internal transmission
I need YEAR, MAKE and MODEL of vehicle, and ENGINE SIZE and TRANSMISSION type, IF applicable to the question.
I work at a Large, Busy GM Dealership
Last thing, my answers are JUST SUGGESTIONS and ADVICE and you should ALWAYS CHECK with your mechanic for proper diagnosis and repair.
Experience 18 Years GM Dealership experience as an "A" line tech. ASE MasterTechnician. 100% GM certified MTC Certified.
Education/Credentials High School graduate. No College or higher learning.
Question Dear Sir; I want to know what effect a change in intake air temperature has upon my truck's PCM. Does increasing or decreasing the intake air temp advance or decrease ignition timing, or does it increase or decrease injector pulse width, and by how much? I cannot find any info pertaining to this question. Sincerely yours, Steve
Answer Hi
Here is a breif description of the circuit description:
The intake air temperature (IAT) sensor is a thermistor. The control module supplies the IAT sensor a reference voltage on the IAT sensor signal circuit and a ground circuit. When the IAT sensor resistance is high, indicating a cold sensor, the IAT sensor signal voltage remains near the supplied voltage and decreases the signal voltage as the sensor warms. The control module monitors the IAT sensor signal circuit in order to calculate the temperature of the air entering the engine.
It will set codes and it has an effect on fuel pulse. The PCM will also though look at the ECT (engine coolant temp sensor) for finer fuel control.
