20 Most Recent 2005 GMC Sierra 1500 - Page 7 Questions & Answers

Headlights Circuit Description The headlights are controlled by the body control module (BCM) via the AHL Relay when the headlamp and panel dimmer switch is the AUTO position. When in the AUTO mode, the BCM receives a signal, (voltage) from the ambient light sensor, based on the voltage of the signal of n the sensor the BCM turns the day time running lamp (DRL) lights OFF and the headlights ON. The headlights can also be turned on by placing the headlamp and panel dimmer switch in the head position. The relay coil is fed by the headlamp and panel dimmer switch or the BCM and the battery B+ buss bar in the underhood bussed electrical center (UBEC). The BCM supplies current to the relay based on the input from the ambient light sensor via CKT 352. The relay output feeds the LT HDLP and RT HDLP fuses to supply current to the low and high beam lamps on CKT 1340 and CKT 1240. The ground for both the low and high beam lamps is supplied via CKT 524 and CKT 525 to the dimmer switch. The dimmer switch uses CKT 1850 for a ground to G203. Some circuits are monitored by the BCM, and upon failure may set a DTC. Park/Side Marker and Tail Lamps The park/side marker and tail lamps are split between the following 4 fuses: ?€¢ The FR PRK

?€¢ The LR PRK

?€¢ The RR PRK

?€¢ The TRL PRK

These fuses receive voltage from the park lamp relay. When the headlamp and panel dimmer switch is in the auto position, the body control module (BCM) controls the relay by grounding CKT 1080 based on the input of the ambient light sensor. The park LPS fuse supplies battery positive voltage (B+) to the relay at all times. When the headlamp and panel dimmer switch is in the PARK position, the relay is by passed through the INT PRK fuse. Current flows from the PARK LPS fuse through the headlamp and panel dimmer switch to the INT PRK fuse in order to feed the following fuses: ?€¢ The FR PRK

?€¢ The LR PRK

?€¢ The RR PRK

?€¢ The TRL PRK

Park Lamps Inoperative

Step

Action

Value(s)

Yes

No 1

1. Turn the ignition OFF.
2. Connect a scan tool.
3. Turn the ignition to the ON position.
4. Using the scan tool, check for any DTCs in the body control module (BCM).

Does the scan tool show any DTCs ? -- Go to Diagnostic System Check - Body Control System in Body Control System Go to Step 2 2

1. Turn the headlamp switch to the park position.
2. Connect a test lamp from (back probe) terminal B of the headlamp and panel dimmer switch to ground.

Does the test lamp light? -- Go to Step 4 Go to Step 3 3

Locate and repair the open in CKT 240 (ORN) between the switch and the mid bussed electrical center (MBEC).

Is the repair complete? -- System OK -- 4

Connect a test lamp from (back probe) terminal A of the headlamp and panel dimmer switch to ground.

Does the test lamp light? -- Go to Step 6 Go to Step 5 5

Replace the headlamp and panel dimmer switch. Refer to Headlamp Switch Replacement .

Is the repair complete? -- System OK -- 6

Connect a test lamp from the INT PRK fuse, located in the left bussed electrical center (LBEC), to ground.

Does the test lamp light? -- Go to Step 7 Go to Step 8 7

Locate and repair the open in CKT 74 (LT BLU) between the MBEC and the UBEC.

Is the repair complete? -- System OK -- 8

Locate and repair the open in CKT 74 (LT BLU) between the headlamp and the panel dimmer switch and the LBEC.

Is the repair complete? -- System OK

There is no such thing , What code do you have if any ? There is a purge solenoid for the EVAP system ! evaporative emission system. An there is a vent solenoid , a fuel tank pressure (FTP) sensor. The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP vent valve to atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the control module will command the EVAP purge valve ON, open, allowing engine vacuum to be applied to the EVAP canister. With the EVAP vent valve OFF, open, fresh air will be drawn through the valve and vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge valve into the intake manifold to be consumed during normal combustion. The control module uses several tests to determine if the EVAP system is leaking.

What is model year? Make sure battery has a full charge and battery connections all good. You can't do any testing if the battery is down.

OnStar is tied into the radio and the bcm, if it is not working it could be very expensive to fix. Since the system uses satellite technology, it could be a bad antenna, bad transmitter etc.

I found this info in your owners manual.

Dead short. Grounding to body intermittently.

Normally I would suspect a problem with the steering rack with that symptom. In time you will probably find it gets worse which, in that event, makes a steering rack problem even more likely. As a first point I would have the steering rack checked out. I would not expect to see this on a 2013 Sierra but it depends on type of use and mileage the vehicle has run.

Usually in the fuse box under the hood.

That is the blower motor relay, probably . You have all speeds but high ? High speed has a direct path to the blower motor through a high blow relay . All other speeds go through the blower motor resistor assembly . This relay is part of the blower motor resistor assembly > That is if you have manual HVAC system . Blower Motor Resistor Assembly (CJ3) Under the right side of the I/P mounted to the HVAC box next to the blower motor.

Probably a constant Velocity joint goung bad. Chevk for a torn rubber boot and you will find your problem.

It should be computer controlled, look at the under hood emission decal for specs.

Looking at the schematic diagram for the system(s), the flasher module is the first and only component common to the turn signals and hazard flashers, Unless the replacement module is bad, then there are only two possibilities: Both the Left and Right Turn Fuses in the left instrument panel fuse block are blown, or you have a ground problem from the flasher module.

Do you have normal fuel pressure ? Was it running before you replaced the wires ? Did you remember to install the rotor under the dist cap ? Is fuel spraying out of the injectors when you crank it ?

www.ask.com/mfg.name/make/model/parking/lights/will/not/turn/off/ there can be a lot of problems, the switch inside the car is malfunctioning, shorted open meaning alway on, the micro switch shorted out , even thou theres a short, shorted to stay on. if you have an auto parts store that will do free trilingual code reader, it plugs into the plug underneath the steering wheel, it runs test on the car or trucks computer and gives you a code, look up the code, the auto parts should know what that codes means, if they will not know the code, than come back and the the following information. www.ask.com/mfg.name/make/model/what/error/code/mean/#####/ or find the fuse for the parking brake and pull it out.

Check spark or leak down test