Your vehicle has two cooling fans controlled by three relay's which are energized by the PCM/ECM - engine computer . Does your vehicle have A/C ? Does it work ? Turning on the A/C the fans should come on low speed , do they ? Does the vehicle overheat ? Any code's stored in the PCM/ECM ?
Relay Driven Dual Cooling Fan Diagnostics
Many things could be your problem.
1- light bulbs (most common)
2- no ground or B+
3- defect fog lights switch
You have to find out with a test light or meter.
At the fog light connector. See if you have B+ and good ground.
If yes then the bulb is the defect.
Looks behind the gloves box compartment there is an LCM module that controls the headlamps and lights, in general,
unplug the connector and you will probably find bad wires terminals that are burned. this is your problems with turn signals and headlights
hope it helps.
The fuse box diagram can be found in the owners manual. If no owners manual is available, check on line by entering your vehicle year and info and fuse box diagram. Just type it into your browser.
Without testing we'd only be guessing , could be the control module ,electrical input to the control module , switche's etc... don't know what year so can't direct you in any testing proceduers .
Doesn't work on any speed ? high - low . Does your's have manual or automatic climate control ?
Don't think a fuse problem , blower motor control processor more then likely .
Blower Motor Control Processor
The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive voltage, and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The processor supplies 12 volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.
Look here for fuse location an wiring diagram's http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model an engine size. Under system click on HVAC , subsystem HVAC controls . click the search button then click on the 5th blue link . This show's fuse location an wiring diagram for the blower electrical circuit . If you don't know where the rear fuse box is ,it's under the rear seat . It would be easier to just check under the passanger side dash at the blower motor control processor at the orange wire .
Do you know how to test electrical circuits with a voltmeter ?
GMC Yukon HVAC Blower Motor Won Turn On
may need a transmission or overhaul that one so take it easy on it. changing the fluid and filter may help but sounds like the valve body is dirty and the trany cant shift like a new one.
You may have low vacuum pressure which can screw up the fuel regulator as well as shift points. I would start by checking for vacuum at idle, and if low, check for a disconnected, broken or kinked hose.
Hey Ben, you might want to try changing the transmission filter and fluid - dirty,messy job but not difficult or spendy. Parts readily obtainable at local Auto Zone or equivalent store. 1- raise front of car and secure with jack stands. 2- loosen transmission pan bolts starting with the rear ones until fluid begins to drip into drain receptacle ( no drain plug so you need to slightly loosen pan for drainage) 3-once fluid has stopped dripping remove entire pan. 4-filter is held in place by clips that allow it to slide out at an angle remove and replace with new one-after that just reverse procedure remembering to tighten bolts in a 'star' pattern so as to have even pressure on gasket for a proper seal. Let me know how it goes - Bonnies rule!!
When it will not start check to see if it has fuel pressure, the fuel pressure test port is in on the fuel pipe that supplies the fuel injectors. You can rent the tool to check the pressure or borrow it from Autozone.
What's missing ? Does it have spark ? Pull a plug wire off the vehicle an see if it has spark ! Buy a fuel pressure gauge an hook it to the schrader valve on the fuel injector rail . Is there fuel pressure ? Does the engine have compression ? No Start Diagnostic Basics EricTheCarGuy
The sensor is on the back side of the engine/firewall, in the exhaust. You can see it. You need a 3/8 ratchet, 12 inch extension. swivel and a O2 sensor socket. 22 mm. Find it, unplug it. remove it.
