What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[97audia4]

I hate that bolt. It’s the same on the NBS. There always has to be that one.

I have a little more room with it being ory headers but it still sucked.

I attempted the second go around on the front difft fill bolt . I am going to weld a nut on it , it's stripped to bad that it's now a 15mm not 19m. I tried heat and kroil and a stripped stocket set .

 

[swathdiver]

Been eyeing a set of power running boards, anyone ever swap a set from an esky to a tahoe (both nnbs)?

We usually see guys ditching them for fixed as they do not like inclement weather and get stuck.

 

[Kee Fuller]

Been eyeing a set of power running boards, anyone ever swap a set from an esky to a tahoe (both nnbs)?

Q

Got my eyes on an aftermarket pair.

 

[Leo1103]

We usually see guys ditching them for fixed as they do not like inclement weather and get stuck.

I probably wont ever use them to be honest, I just hate how the stock ones look

Q

Got my eyes on an aftermarket pair.

What brand?

 

[Hi-psi]

In Today's Episode of How The Yukon Wheel Turns...

So, called McGaughy's and they really didn't have any info or ideas. Just said to make sure no pinched wires, etc. Certain that isn't the case.

This morning on the way to work, I disabled the Traction Control & Stablitrak (by holding the button down for like 10 seconds to turn both off) and aside from the Traction Control light being constantly illuminated (as expected) it drove perfect. No brake pulsing during sharp slow speed turns where it was happening. Not sure that helps any, but certainly affirms it's something to do with the vehicle for whatever reason thinking there's a loss of traction or lockup situation. Just need to figure out if it's because of a wheel speed sensor (not sure how it could be since they're all new, and all reading consistent and correct), or the steering position sensor (not sure how it could really be this either, but considering all things).

I'm going to poke around my scan tool this afternoon and see if there's a way to view the signal/data from the steering position sensor to see if there's anything obvious going on there.

Ok, so now on to something maybe completely unrelated....maybe not. I've had my Denali for about a year and a half now. I'm well aware of the GM regulated voltage charging system and how you'll see the voltage gauge at times range between 12-15'ish as the system does it's thing. That said, since I've had my Denali, it wasn't uncommon when the headlights were on for me to see a very quick flicker/dimming of them when letting off of the gas, say while exiting the freeway and coasting down the exit ramp, or at low rpm's when say the electric fans kicked on. Never gave it much thought. Well, this morning, it was much more pronounced. Whenever I would let off the gas taking an exit or the fans would kick on the headlights would noticeably flicker/flash/momentarily dim. I get all the way to work, pull into a parking spot, shut it off. Get out, realize I've pulled in a bit crooked, so I go to crank the vehicle, as soon as I hit the key to start it the entire electrical system blips. Nothing, dead. Turn the key off, back on, starts fine. Straighten up, shut it off, pop the hood, check all the battery connections ensuring they're tight. Nothing obvious.

Doing a little forum searching, a few others have reported the headlight dimming situation, and some other electrical oddities which were seemingly rectified by replacing the alternator, even when their current one "tested" good. Maybe something internal was bad and it was no longer able to regulate the voltage like it should. Battery is less than a year old so pretty sure that can be ruled out. It's never had a problem starting, or anything prior to this.

I welcome any thoughts, ideas, or insight on both situations.

 

[the_tool_man]

In Today's Episode of How The Yukon Wheel Turns...

So, called McGaughy's and they really didn't have any info or ideas. Just said to make sure no pinched wires, etc. Certain that isn't the case.

This morning on the way to work, I disabled the Traction Control & Stablitrak (by holding the button down for like 10 seconds to turn both off) and aside from the Traction Control light being constantly illuminated (as expected) it drove perfect. No brake pulsing during sharp slow speed turns where it was happening. Not sure that helps any, but certainly affirms it's something to do with the vehicle for whatever reason thinking there's a loss of traction or lockup situation. Just need to figure out if it's because of a wheel speed sensor (not sure how it could be since they're all new, and all reading consistent and correct), or the steering position sensor (not sure how it could really be this either, but considering all things).

I'm going to poke around my scan tool this afternoon and see if there's a way to view the signal/data from the steering position sensor to see if there's anything obvious going on there.

Ok, so now on to something maybe completely unrelated....maybe not. I've had my Denali for about a year and a half now. I'm well aware of the GM regulated voltage charging system and how you'll see the voltage gauge at times range between 12-15'ish as the system does it's thing. That said, since I've had my Denali, it wasn't uncommon when the headlights were on for me to see a very quick flicker/dimming of them when letting off of the gas, say while exiting the freeway and coasting down the exit ramp, or at low rpm's when say the electric fans kicked on. Never gave it much thought. Well, this morning, it was much more pronounced. Whenever I would let off the gas taking an exit or the fans would kick on the headlights would noticeably flicker/flash/momentarily dim. I get all the way to work, pull into a parking spot, shut it off. Get out, realize I've pulled in a bit crooked, so I go to crank the vehicle, as soon as I hit the key to start it the entire electrical system blips. Nothing, dead. Turn the key off, back on, starts fine. Straighten up, shut it off, pop the hood, check all the battery connections ensuring they're tight. Nothing obvious.

Doing a little forum searching, a few others have reported the headlight dimming situation, and some other electrical oddities which were seemingly rectified by replacing the alternator, even when their current one "tested" good. Maybe something internal was bad and it was no longer able to regulate the voltage like it should. Battery is less than a year old so pretty sure that can be ruled out. It's never had a problem starting, or anything prior to this.

I welcome any thoughts, ideas, or insight on both situations.

Good, detailed info. Thanks for that. I am experiencing the flickering you refer to exactly as you describe it. I just replaced the battery and had the alternator load tested. They measured the output under various loads and engine rpm. Their machine pronounced the alternator healthy. The only thing I haven't done is go through all my grounds, as is frequently recommended. I'll probably do that next weekend. I'll report back if I learn anything of interest.

In general, if your electrical system is seeing voltage fluctuations, it stands to reason that this may cause (or contribute to) issues with sensors. Without knowing the actual signals the sensors use (voltage, current loop, whatever), I won't attempt to speculate further. But it may well be the cause of your issue in my opinion.

Specifically to your TC warning, maybe one of the sensors isn't properly grounded. I haven't touched mine. But on other vehicles I've had, it was important to make sure the body of the sensor directly contacts metal. No sealant, thread locking compound, grease, dirt, etc. I suspect you've eliminated that as a possibility. But for the greater good, I mention it.

Lastly, while the probability seems remote, you might have a brand new, defective sensor, or a bad cable, connector, or whatever. If your Tech2 can pinpoint which sensor it is, maybe you could swap it to another wheel to see if it moves with the sensor or not. Keep the info coming. We'll get it figured out.

 

[Hi-psi]

Yeah, seems like I have two (potential) issues going on, maybe related, maybe not.

Regarding our shared headlight dimming thing. If you trace the negative battery cable down from the battery, right where it's by one of the A/C lines is a three wire electrical plug. This is the plug for the GM voltage regulation system thing. If you unplug this, the system will then function just like a traditional battery/alternator system....at least from what I've read. I unplugged mine today before driving home from work and the entire way home the voltage gauge stayed well above 14, even when stopped at redlights and the fans kicked on. Admittedly I don't have a detailed understanding of how the GM voltage regulation system works. If perhaps it's something internal in the alternator that modulates it's functions, I suppose it's logical that it may in fact "test" good, even though it may not be functioning properly if whatever method is used to test it is generic, or not advanced/customized to invoke the different charge/function scenarios the alternator will see in regular use. I'm probably over thinking it as I have a tendency to do. Regardless, I was going to leave my plug unplugged when I drive to work in the morning and see if I notice any difference in the headlight behavior.

It would be a crazy coincidence, but I too was thinking that if I were having some voltage issues because of a bad alternator, that could potentially be causing the wheel speed sensor problem. Although that problem only manifested literally right after putting on the lowering kit, I've replaced all four sensors and viewed their data with my scanner and nothing seems abnormal. When I have the time I was going to tear back into the front, remove the sensors, clean the hub mounting surface really good, and even though I'm sure they were fully seated when I replaced them, make 178% sure this time they're fully seated and completely flat when installed and tightened down.

Even though I hate just throwing blind money and problems, part of me wants to just go ahead and replace the alternator. I bought my Denali with over 200k on it already and have no way of knowing if it's the original alternator or ever been replaced before.

 

[89Suburban]

Yeah, seems like I have two (potential) issues going on, maybe related, maybe not.

Regarding our shared headlight dimming thing. If you trace the negative battery cable down from the battery, right where it's by one of the A/C lines is a three wire electrical plug. This is the plug for the GM voltage regulation system thing. If you unplug this, the system will then function just like a traditional battery/alternator system....at least from what I've read. I unplugged mine today before driving home from work and the entire way home the voltage gauge stayed well above 14, even when stopped at redlights and the fans kicked on. Admittedly I don't have a detailed understanding of how the GM voltage regulation system works. If perhaps it's something internal in the alternator that modulates it's functions, I suppose it's logical that it may in fact "test" good, even though it may not be functioning properly if whatever method is used to test it is generic, or not advanced/customized to invoke the different charge/function scenarios the alternator will see in regular use. I'm probably over thinking it as I have a tendency to do. Regardless, I was going to leave my plug unplugged when I drive to work in the morning and see if I notice any difference in the headlight behavior.

It would be a crazy coincidence, but I too was thinking that if I were having some voltage issues because of a bad alternator, that could potentially be causing the wheel speed sensor problem. Although that problem only manifested literally right after putting on the lowering kit, I've replaced all four sensors and viewed their data with my scanner and nothing seems abnormal. When I have the time I was going to tear back into the front, remove the sensors, clean the hub mounting surface really good, and even though I'm sure they were fully seated when I replaced them, make 178% sure this time they're fully seated and completely flat when installed and tightened down.

Even though I hate just throwing blind money and problems, part of me wants to just go ahead and replace the alternator. I bought my Denali with over 200k on it already and have no way of knowing if it's the original alternator or ever been replaced before.

So I unplugged mine and been driving around at full voltage for a couple weeks. Runs much better, seems more powerful. No dim lights. But I took a highway trip one night and pulled over for a rest stop. I got out and smelt a electrical burning smell. Kinda freaked me out so I plugged it back in.

 

[Kee Fuller]

I probably wont ever use them to be honest, I just hate how the stock ones look



What brand?

https://www.electricstep.com/AMP-Research/pc/Chevy-Tahoe-2007-2014-p52.htm

 

[Hi-psi]

So I unplugged mine and been driving around at full voltage for a couple weeks. Runs much better, seems more powerful. No dim lights. But I took a highway trip one night and pulled over for a rest stop. I got out and smelt a electrical burning smell. Kinda freaked me out so I plugged it back in.

Interesting...

Found this on the net regarding the system..

The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:

• Battery Sulfation Mode

• Charge Mode

• Fuel Economy Mode

• Headlamp Mode

• Start Up Mode

• Voltage Reduction Mode

The engine control module (ECM) controls the generator through the generator turn on signal. It monitors the generator performance though the generator field duty cycle signal circuit. The signal is a 5-volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-95 percent. Between 0-5 percent and 95-100 percent are for diagnostic purposes. The following table shows the commanded duty cycle and output voltage of the generator:


The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is a 5-volt PWM signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-99 percent. Between 0-5 percent and 100 percent are for diagnostic purposes.

Battery Sulfation Mode
The BCM will enter this mode when the interpreted generator output voltage is less than 13.2 volts for 45 minutes. When this condition exists the BCM will enter Charge Mode for 2-3 minutes. The BCM will then determine which mode to enter depending on voltage requirements.

Charge Mode
The BCM will enter Charge Mode when ever one of the following conditions are met.

• The wipers are ON for more than 3 seconds.

• GMLAN (Climate Control Voltage Boost Mode Request) is true, as sensed by the HVAC control head. High speed cooling fan, rear defogger and HVAC high speed blower operation can cause the BCM to enter the Charge Mode.

• The estimated battery temperature is less than 0°C (32°F).

• Battery State of Charge is less than 80 percent.

• Vehicle Speed is greater than 145 kph (90 mph)

• Current Sensor Fault Exists

• System Voltage was determined to be below 12.56 volts

• Tow/Haul Mode is enabled

When any one of these conditions is met, the system will set targeted generator output voltage to a charging voltage between 13.9-15.5 volts, depending on the battery state of charge and estimated battery temperature.

Fuel Economy Mode
The BCM will enter Fuel Economy Mode when the ambient air temperature is at least 0°C (32°F) but less than or equal to 80°C (176°F), the calculated battery current is less than 15 amps and greater than -8 amps, and the battery state of charge (SOC) is greater than or equal to 80 percent. Its targeted generator output voltage is the open circuit voltage of the battery and can be between 12.5-13.1 volts. The BCM will exit this mode and enter Charge Mode when any of the conditions described above are present.

Headlamp Mode
The BCM will enter Headlamp Mode when ever the headlamps are ON (high or low beams). Voltage will be regulated between 13.9-14.5 volts

Start Up Mode
When the engine is started the BCM sets a targeted generator output voltage of 14.3 volts for 30 seconds.

Voltage Reduction Mode
The BCM will enter Voltage Reduction Mode when the calculated battery temperature is above 0°C (32°F). The calculated battery current is less than 1 amp and greater than -7 amps, and the generator field duty cycle is less than 99 percent. Its targeted generator output voltage is 13 volts. The BCM will exit this mode once the criteria are met for Charge Mode.

Instrument Panel Cluster (IPC) Operation
Charge Indicator Operation
The instrument panel cluster (IPC) illuminates the charge indicator and displays a warning message in the driver information center (DIC) when the one or more of the following occurs:

• The engine control module (ECM) detects that the generator output is less than 11 volts or greater than 16 volts. The IPC receives a GMLAN message from the ECM requesting illumination.

• The BCM determines that the system voltage is less than 11 volts or greater than 16 volts.

• The IPC receives a GMLAN message from the body control module (BCM) indicating there is a system voltage range concern.

• The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

• The ignition is ON, with the engine OFF.

Battery Voltage Gauge Operation
The IPC displays the system voltage as received from the BCM over the GMLAN serial data circuit. If there is no communication with the BCM then the gauge will indicate minimum.

Utilities and light duty full size pickups are equipped with a new regulated voltage control (RVC) system. This system turns off the alternator when it is not required in order to improve fuel economy. The generator will turn back on when additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems which usually maintain a more consistent reading of 14 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted.[/qoute]