98 Suburban 4wd 5.7 to 01 6.0L questions

[shmiet]

The LS computer doesn't send the correct fuel level signal for your cluster. You need a fuel segment swap with your tables flipped. Your engine coolant temp signal will come from the original sensor that was in your 5.7- I suggest turning it down and using an M10x1.5 die so it will fit in the place where the head coolant plug is. Fuel pressure gauge can be hooked up to the LS pressure sensor. PRNDL will need splicing-i couldn't get mine working fully yet.

[genIIIdude]

Thanks - I'm sending my computer to Lextech for the fuel gauge issue - he also told me to run the 98 oil and water temp sensors to get the gauges to read.

[shmiet]

My LS oil sensor had the same plug(single wire) as my obs sensor. I just plugged it in and it reads fine. Dunno if I got lucky or something haha
Good to hear your on track though!

[genIIIdude]

The oil sensor connector on my truck has 4 wires?

[shmiet]

4? Maybe suburbans are different

[genIIIdude]

Just put the OBS oil sensor in (3 wire by the way, not 4) and still no oil pressure on gauge. Also - the fuel pump runs all the time now - I unplugged the new OBS oil sensor and the fuel pump turns off?! What gives?

[kewljay223]

i had this issue also. turned out to be a bad oil pressure sensor (i hooked it up incorrectly and fried the contacts shut) which caused the pump to run continuously. the way it works is you have the pressure switch in parallel with your fuel pump relay. when you turn the key to on/start, the pcm will kick the relay on for 2 seconds to build the needed fuel pressure at the rails. The engine fires and now oil pressure has been created and obviously stays until engine get shut down. this pressure closes the contacts in your oil pressure switch which alows voltage to power your fuel pump continuously until pressure is dropped. This is why you can still hear your pump running in the tank for several seconds after you kill the motor. takes a bit for the oil pressure to bleed down and open the contacts in the oil pressure sensor. I believe its also a safety precaution in case of severe accident like a roll over.... do you want your fuel pump stil running after you roll over and are unconcious just cuz your key is still in the ON position? i sure dont!!!

anyway, i know all this cuz i was having a similar issue and had to dig through all the wiring diagrams. makes complete sense to me now and i opted to keep it wired that way. some guys delete it but i personally like the extra safety. so it sounds like you have it wired incorrectly AND/OR your sensor is shot like mine was. i think it was like 10 bucks at autozone. cheap thing to replace.

BTW, im sure youve figured it out by now but ill say it anyway. The sensor doubles as a oil pressure sensor AND fuel pump switch. thats why there are 3 wires on it.

TAN - goes to oil pressure gauge on your cluster
ORANGE - +12v going to one side of contacts on switch
GRAY- comes off of other side of contacts of switch and goes to fuel pump


PHEW!! hope that helps

P.S. i drove around for a week having to get out and unplug the fuel pump everytime i parked somewhere before i figured this out....

[genIIIdude]

Another new sensor - fuel pump shuts off but still no reading on the gauge. hooked up a manual gauge to make sure I have pressure, all is well there. Going to chase down the wiring now....

[genIIIdude]

Found my problem - I had removed a plug that is located behind the glove box and goes into the engine bay through the fire wall, well, that is where the instrument panel is grounded. The only reason I removed it was to get the stock wiring harness out of the way for my install. Both water and oil gauges are functional. The tach also works but is about 600 rpm shy of reality. How do I fix that? Can I do it with my HP Tuners?

I had a thought with my fuel gauge issue, and yes I know it may be extreme. I'm thinking of getting a newer fuel tank from a Suburban to replace my 98's. That way I'll be running the newer fuel tank and fuel pump assembly and should have no issues with the LS ECM reading the fuel sender. The only issue that I see could be that the stock 98 gauge would still not read the info coming from the LS ECM - does anyone have any experience with this?

I did drive it up the road the other day - this 6.0 has a lot more power than the old, tired 5.7! Thanks Lextech for your help with the wiring - retrofitting the stock 5.7 harness to the LS engine is the way to go......For me anyways.

[Lextech]

I had a thought with my fuel gauge issue, and yes I know it may be extreme. I'm thinking of getting a newer fuel tank from a Suburban to replace my 98's. That way I'll be running the newer fuel tank and fuel pump assembly and should have no issues with the LS ECM reading the fuel sender. The only issue that I see could be that the stock 98 gauge would still not read the info coming from the LS ECM - does anyone have any experience with this.

I have never tried that, BUT, I don't think so. The issue is not the PCM receiving info from the fuel sender. The issue is the PCMs output to the gauge. It needs to be changed in the tune.

Jeff