larrys project

iTrader: (1)

I am baffled & could use some help. I have a 2004 5.3 with a Speartech harness, I have had this set up running fine about 3 monthes ago. I tried to start today after I installed the cab & bed, & as soon as I turn the ignition on, the fuse blows. I looked for a pinched wire & found none. I chased the problem down to the drivers side oxe sensor. When I unplug the sensor then the fuse dont blow. I took my test light & found that I have 12 volts to the brown wire at the ox sensor connector. (both L/H & R/H) Is this correct to have 12 volts at the sensor??

350SS

iTrader: (38)

I'm not sure on the color wire, but yes, there should be 12v. The sensors are heated to get them up to operating temperature, and closed loop operation sooner. If there's something wrong with the heating element then it might cause a problem resulting in a blown fuse. You could check to see if it is the O2 by plugging in the O2 from the opposite bank into the one you already unhooked, and see if it has the same effect of blowing the fuse. Hope this helps.

larrys project

iTrader: (1)

thanks 350SS, I will try that in the morning, that makes me feel better knowing that it should have 12 volts. now I can sleep better tonight

G-Body

iTrader: (4)

The pink wires should have 12V. The black is a ground. Purple is the sensor output and tan is the low side of the sensor(ground).

busta9876

iTrader: (3)

Factory GM schematics shows pink wire, pin D of all 4 o2 sensors feeds 12v positive to the oxygen sensor heaters.

Pin C of the O2 sensor connector is the heater low control going to the PCM.

here's the wire schematic for 04 C/K truck



good luck

350SS

iTrader: (38)

Allright, just looked up the schematic for the O2s and the only wire listed as Brown was for the Low (ground) side of the Bank 1 Sensor 2 (after cat) O2 sensor. The ground obviously shouldn't have 12v, but since this is a Speartech harness, I'm not sure if they stick with the GM wire colors or not.

Here's some better specifics

Pin
Wire Color
Circuit No.
Function

For Bank 1:
A
TAN
1664
HO2S Low Signal Bank 1 Sensor 1

B
PPL/WHT
1665
HO2S High Signal Bank 1 Sensor 1

C
BLK/WHT
3113
HO2S Heater Low Control Bank 1 Sensor 1

D
PNK
539
Ignition 1 Voltage

For Bank 2:
A
TAN
1667
HO2S Low Signal Bank 2 Sensor 1

B
PPL
1666
HO2S High Signal Bank 2 Sensor 1

C
LT GRN
3212
HO2S Heater Low Control Bank 2 Sensor 1

D
PNK
539
HO2S High Signal Bank 2 Sensor 1

350SS

iTrader: (38)

damn...you guys are quick, beat me to it lol!

larrys project

iTrader: (1)

now I,m worried again, I am pretty sure I was getting 12V at the brown wires. My set up (harness) does have the front sensors removed, if that makes any diff.

G-Body

iTrader: (4)

Front sensors or rear are removed? You need the fronts, but you could remove the rears. It shouldn`t make a difference on wire color though.

larrys project

iTrader: (1)

I believe John at Speartech said the fronts would be removed. I am not running cats, just 1 pair of sensors about 10" aft of the exhaust manifold. What baffles me is that it was working fine when I had the truck running before. I thought things were going too good with this late model computer stuff.