evldoer

iTrader: (7)

Have a lq9 engine, bought an aftermarket harness, and ecm from same vendor. After hooking everything up, and powering up everything, the 20 amp fuse blew that powers the o2 sensors and the MAF. (LS7 style MAF). I then chased the wires, didnt find anything wrong. Prior to powering the system up I had to extend the 4 wires for bank 2 o2 sensor. Did this with power off and ecm unplugged, soldered and heat shrink the wires. I replaced the fuse, powered it up, and fuse burned out again. Rechecked everything, and snapped another fuse. I think I went through about 4 fuses, and now the fuse stays intact.
Ok then I took car to the tuner. He was getting 450mv readings on both banks of the O2 sensors. He then checked the wires and said the wires were pinned wrong at the plug for the O2 sensors. After pinning them properly, still no change.
I chased the wires from the O2 plug to the ecm. They have continuity, ohms are good. Have ground and 12.65 volts at O2 plug.
The tuner reflashed ecm with a stock 02 truk tune, still no change, still reading 450mv.
Is it possible the ecm was fried from the wires being pinned wrong to begin with? Was the ecm being feed 12 volts on the signal high or signal low? Would this cause damage to the ecm that cant be fixed?
Tomorrow the plan is to try a different ecm. Any thoughts or suggestions?

jimmyblue

iTrader: (11)

The PCM jams the voltage to 450mV when there's an
O2 sensor fault (real or imagined). Killing the codes
the wrong way can let this go on without an indication.

I think since this is a lashup, chasing the 4 wires of each
from PCM connector to sensor (you do have the right
pinout info for the PCM P/N, right?) is worthwhile. You
might also wonder why whatever was blowing fuses,
quit blowing them. Might split the ENG SEN into individual,
lower current feeds to one sensor apiece (cost you a few
inline fuse holders?) so you can get an idea of what is
the problem.

Bowtie316

iTrader: (1)

I checked once before building a harness and the o2 heaters draw something like 400milliamps to heat up, nowhere close to being able to blow a 15 amp fuse. Something was definately wired wrong. I would check that the way the harness is wired matches the o2 sensors you used. I have heard that some o2 sensor are wired differently.

axelg89

I have the exact same problem. My o2 values wont move and I really want to get this thing working. If you solve your problem please get back to me and I'll ofcourse do the same. My car is a 1969 Corvette c3 with an LS1 from a 2002 Camaro (also t56).

Have tried measuring the connector and get the following with the car on:
A:~1.4V, B:~4.7V, C:~GROUND, D:~12.3V (ign).


Do you get the same? Does this look right?

Any input is greatly appritiated.
Thanks

evldoer

iTrader: (7)

Thanks for all the help guys. After trying another ecm, still no change in the situation. I bought 2 new oxygen sensors and installed them. Now everything is normal, and the signal is doing what it is supposed to.
So basically what happened was the harness I bought was pinned incorrectly at the O2 connectors. It was sending power to the signal wires on the sensors, thus blowing them out. After the tuner re-pinned the harness, we went under the assumption that the sensors were not damaged. Well that wasnt the case. They were damaged, and replacing them fixed the problem. Now we have another happy ls on the road. Thanks again for the help guys!!

axelg89

what sensors did you replace them with?

thanks

evldoer

iTrader: (7)

The first set were Denso. So were the pair I replaced them with. Have 400 miles on car and so far so good with the sensors.