Electrical - where to begin

[swathdiver]

Hello, I have 2005 Tahoe...

Welcome to the forum from Florida Popeye!

 

[Moosemoon]

Hello, I have 2005 Tahoe, I replaced Knock sensor's soon after I bought it, as code came up. They will cause ur Milage to drop drastically, I was down to 10mpg ! Bad Knock sensor's can cause engine damage if driven alot & not replace. As for Ground wire's, your Batter Only Has ONE, its the main battery ground! No other wires to follow from your battery! My Break lights stopped working, Replaced Pedal Switch, still no break lights. I haven't found the problem yet, there are many Ground wires under vehicle, if u have Tow Package, check wires there also. I know my info doesn't help much but I wanted to tell you mainly about Battery Ground, no vehicle has numerus grounds from battery ground. Not Factory anyhow!

Thanks for the info.
GM dealer mechanic says the knock sensors are working correctly. Wants to do extensive (read expensive) electrical diagnosis. SOOO I am trying to figure out what I can do to narrow things down a bit.

Right now, for the knock sensors, I’d like to check the PCM connector as there is a pin specifically for that. Not sure where to begin with airbag codes yet.

There are other historical codes that the dealer cannot replicate. I was told the dealer mechanic checked to see if there were obvious problems - but I’m not convinced he did. Worked with Yukon less than an hour. Nice thing is, they didn’t charge me. Guess they figure they’ll make up for it on the backend

 

[MassHoe04]

Can you please clarify if these are active codes with check engine light on and airbag light on. Or are they simply historical codes? You can disregard about 3/4 of the nonsense that has been posted thus far

Was I part of the nonsense? Not intentionally... When I was talking about checking grounds, I may have inter-tangled mention of main battery ground then rambled into mention of checking other ground locations that could cause weird electrical behaviors. Especially grounds for the PCM and BCM being big culprits with a lot of demons people fight on their trucks.

I was suggesting it wouldn't hurt to verify key ground points up in the engine bay and on the body mount by the driver's door.

Apologies if I contributed to any nonsense. No harm intended.

 

[Moosemoon]

Was I part of the nonsense? Not intentionally... When I was talking about checking grounds, I may have inter-tangled mention of main battery ground then rambled into mention of checking other ground locations that could cause weird electrical behaviors. Especially grounds for the PCM and BCM being big culprits with a lot of demons people fight on their trucks.

I was suggesting it wouldn't hurt to verify key ground points up in the engine bay and on the body mount by the driver's door.

Apologies if I contributed to any nonsense. No harm intended.

No harm done. Thanks for your input!

 

[Doubeleive]

Was I part of the nonsense? Not intentionally... When I was talking about checking grounds, I may have inter-tangled mention of main battery ground then rambled into mention of checking other ground locations that could cause weird electrical behaviors. Especially grounds for the PCM and BCM being big culprits with a lot of demons people fight on their trucks.

I was suggesting it wouldn't hurt to verify key ground points up in the engine bay and on the body mount by the driver's door.

Apologies if I contributed to any nonsense. No harm intended.

No, always a good idea to check grounds. the codes particularly srs codes usually aim at a specific problem, like the drivers airbag usually that is a bad connection, the front impact sensor's do go bad from being exposed to the elements, that could tested by swapping said sensor left to right and see if the code follows.
knock sensors are a cross your fingers and hope they work kind of thing it's not uncommon to have to do them twice especially if oem was not used.
brake switch control low voltage could be bad brake switch, poor connection on the light harness or bulb connectors, poor ground on the light harness which is also exposed to the elements
fuel pump module is also exposed and the harness getting corroded is a known issue
personally I would try and address each specific code to rule it in or out and then move on to other possible causes, doesn't seem like these are a bunch of random codes that would be caused by something else

 

[MassHoe04]

No, always a good idea to check grounds. the codes particularly srs codes usually aim at a specific problem, like the drivers airbag usually that is a bad connection, the front impact sensor's do go bad from being exposed to the elements, that could tested by swapping said sensor left to right and see if the code follows.
knock sensors are a cross your fingers and hope they work kind of thing it's not uncommon to have to do them twice especially if oem was not used.
brake switch control low voltage could be bad brake switch, poor connection on the light harness or bulb connectors, poor ground on the light harness which is also exposed to the elements
fuel pump module is also exposed and the harness getting corroded is a known issue
personally I would try and address each specific code to rule it in or out and then move on to other possible causes, doesn't seem like these are a bunch of random codes that would be caused by something else

I had a code my Tech 2 identified as the LF impact sensor. Open circuit, IIRC. Forgot the code number... But anyway, I went right for that on replacement, rather than bother swapping the right side over. Tech 2 was right! It was a bad sensor on left side. I was diagnosed and done in no time.

 

[Moosemoon]

No, always a good idea to check grounds. the codes particularly srs codes usually aim at a specific problem, like the drivers airbag usually that is a bad connection, the front impact sensor's do go bad from being exposed to the elements, that could tested by swapping said sensor left to right and see if the code follows.
knock sensors are a cross your fingers and hope they work kind of thing it's not uncommon to have to do them twice especially if oem was not used.
brake switch control low voltage could be bad brake switch, poor connection on the light harness or bulb connectors, poor ground on the light harness which is also exposed to the elements
fuel pump module is also exposed and the harness getting corroded is a known issue
personally I would try and address each specific code to rule it in or out and then move on to other possible causes, doesn't seem like these are a bunch of random codes that would be caused by something else

Thank you for the input. Since the dealer cannot replicate the fuel transfer pump, fuel level sensor or brake codes (not even as historical) we are choosing to work on the airbag codes and knock sensor codes.
Other than bad gas mileage, the Yukon runs well. The dealer has said the knock sensors are good. O2 sensor also replaced. So think we are done throwing parts at the P0332 code.
Finally have a little sunshine - despite cold north wind. Going out to check ground on battery and the big one at the back of the engine bay.
Next step is to remove fuse box and check all connections to the PCM and their tributaries.
Wish me luck - I need it!

 

[Moosemoon]

I had a code my Tech 2 identified as the LF impact sensor. Open circuit, IIRC. Forgot the code number... But anyway, I went right for that on replacement, rather than bother swapping the right side over. Tech 2 was right! It was a bad sensor on left side. I was diagnosed and done in no time.

Will see what I can find on that sensor. Thanks

 

[Moosemoon]

So far grounds look good. Starting on other tomorrow

 

[MassHoe04]

So far grounds look good. Starting on other tomorrow

Good baseline to start from. At least you won't be chasing all other systems forever, only to find out problems were chassis grounds!

I am sure the expert electrical gurus will get you figured out pretty quickly.