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2003 2006 Trailblazer

Looks like an interesting community, I thought I would try to get some advice. We purchased a 2003 Chevy Trailblazer on the cheap because it had an engine fire. Looked like the air conditioning hose was leaking around the connection between tube and hose, a coil sparked and lit the truck on fire. This was judging on the burns. Either way, I went to a yard, found a Trailblazer with the same 4.2 six, pulled what I could of the harness, cut the rest. Do not know what pinout file I had when I did it, but the only thing that did not work was the indicator light for the gear selector, that I ended up adding a ground to get to work. But when that happened, I started to realize that just using the 2006 neutral safety switch and the 2006 forward o2 sensor was not the answer. Now we have to get to emissions. Yesterday, the battery started to overcharge, got to 19 volts, ended up needing to replace the alternator, but now there is a surge and the codes are screaming 02 heater resistance. So I got subscribe to alldata and got the o2 schematics to see that the wiring is coming off of different pins, at least it looks that way to me. Cant get thru emissions with the check engine lite on so it is time to start digging again. I just thought I would find a place to post this and see if there are any ideas about needing to look into the pins. I did take the harness and pcm from the donor truck that turned out to be an 06.

2006o2 !

R134 refrigerant isn’t flammable… if the AC caused a fire, some bonehead recharged it with propane.

Might help if you posted the actual codes you have set. The O2 heater isn’t exactly complicated but must be wired so the ECU recognizes it is there. Is the schematic for an 03 or an 06?


Can we assume you’ve checked that 10Amp fuse at the top of your wiring diagram . . . ?!

Your high charging voltage may have zapped the heating element in the sensor.

being a new member, they only let me post one picture,2003o2 03

2006o2 06

same numbers going to the wires at the connector, different connector in 06, looks like different pinouts for the o2 sensors.

I did light my face on fire once trying to fix a leak of refrigerant, so might not be accurate about being flammable.

So change the pinouts. Use the 03’s harness side connector body and swap for the 06’s connector body so the sensors plug in. Alternatively, I’d guess buy 2 new O2 sensors (the heaters fail before the sensors) from an 06 and plug directly.

I can barely read the schematics, BTW. Resolution is pretty poor. You need to trace the harness connector by connector to make sure they all match and fix anything that doesn’t. You can clearly see things changed in 3 years, as they often will. The changes may be small but can be very significant.

It is tedious and painful but you have no choice if you want this to pass emissions.

It was tedius splicing the two back together again or it would have been a week to get the BCM wires pulled. Never de pinned a car terminal though, looks like the connector part is expanded in the cluster. Is it cutting the wire, then drawing it thru the front and replacing it where it needs to go? Has anyone done that before? I am hoping there is an actual wire in the correct place that goes somewhere else and I can just switch the wiring, but if there is not a wire where it needs to be, then I will need to move one there.

NO, no, no! The pins have a little lock tab on them that can be depressed with a special pick tool available at any auto parts store. They are “pull to seat” pins that are inserted from the back and then a small tug on the wire to seat. You need to push the wire forward and depress the tab so you can pull it out.

If you’ve cut and re-attached wiring, I sure hope you soldered the wires and added heat shrink to seal them or used sealing solderless crimp connectors. Anything else will be a nightmare in very short order.

ok, little upset there are not pinout diagrams on alldata. I will get the pick assortment to find them. I am guessing certain functions are running at default with no signal. Check engine for emissions, 02 were always on, but new vehicle in chicagoland you get a year before emissions are due to a new owner. Trans is a little funky, but that was one of the connectors I had the pinout diagram for the 2004 that made everything work. I did solder and heatshrink every connector I did already, just seemed like colors were alike even though they went to different places.

Well, since I started this a year ago, and it ran well enough until now, I really saw so many pin differences. I did finally get thru the security of the PCM I took with the harness, there was so much running in default. Both 02’s were running in default, basically sitting at 450mv, the heater had power from the fuse box, and were always on, but no fuel trim just sucking fuel.
Ended up needing the sequence of try to start, leave it on til security went off, wait 10 seconds, try to start, leave it on til security went off, wait 10, until it started. The other way I was doing it was with resister keys that chevy did not have then where you do not go to try to start between steps.

I am in complete amazement how these computer controlled vehicles can actually run and drive under complete default mode.