LS swap computer problems
Thread Starter
Registered User
Joined: May 2014
Posts: 1
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LS swap computer problems I have just completed installing a 4.8 in my 1955 Chevy truck. I used a 2002 GMC Sierra truck as a doner vehicle.
I used everything I could from this truck to keep it simple, engine, wiring harness, computer, instrument cluster, steering column. I did not use the gas tank or it's sending unit.
The engine starts and seems to run fine. I have the low battery indicator showing on the instrument cluster, and do not indicate any heat on the temp gauge. I also don't show the PRNDL indicator in run but do in start. I do show oil pressure and the speedometer and tack work.
I would like to get the temperature gauge working as I think the computer is staying in open loop thinking the engine is still cold. When I plug in an OBD2 tester it tells me my engine is cold. The engine is hot and the sensor has 240 ohms at this time which is what it should be with a hot engine. The wiring from the sensor to the computer is good and shows the same 240 ohms at the computer.
I am thinking there must be a damaged wire somewhere from the swap that has the computer not seeing something. Everything was working when it was in the donor truck.
Any suggestions on this would be appreciated.
Thanks
I used everything I could from this truck to keep it simple, engine, wiring harness, computer, instrument cluster, steering column. I did not use the gas tank or it's sending unit.
The engine starts and seems to run fine. I have the low battery indicator showing on the instrument cluster, and do not indicate any heat on the temp gauge. I also don't show the PRNDL indicator in run but do in start. I do show oil pressure and the speedometer and tack work.
I would like to get the temperature gauge working as I think the computer is staying in open loop thinking the engine is still cold. When I plug in an OBD2 tester it tells me my engine is cold. The engine is hot and the sensor has 240 ohms at this time which is what it should be with a hot engine. The wiring from the sensor to the computer is good and shows the same 240 ohms at the computer.
I am thinking there must be a damaged wire somewhere from the swap that has the computer not seeing something. Everything was working when it was in the donor truck.
Any suggestions on this would be appreciated.
Thanks
Staging Lane
Joined: Mar 2013
Posts: 67
Likes: 0
From: Mount Gambier, Australia
Not sure on how the US vehicles work, but I did a similar conversion in my 1978 pickup using a donor car, and the only way I could get the dash to work properly was install the BCM out of the donor vehicle. All OK now.
TECH Fanatic
Joined: May 2010
Posts: 1,081
Likes: 8
From: Atlanta, Ga
My best guess would be to swap out the sender. Your scanner does not show signal from the sender? Any DTC's? Do you still have the large switch on the transmission selector that has the plug from C100 ?
TECH Resident
Joined: Feb 2014
Posts: 954
Likes: 9
From: Encinitas CA
what happens when you apply the temp sender lead to ground, do you see ground at the computer pin?
If not, I think you have a bad wire in between.
Odd, though that you have fixed 240 ohms.
Also, what is your system voltage? Might want to measure that to see if it is an issue, too.
Is your alternator charging?
Doug
If not, I think you have a bad wire in between.
Odd, though that you have fixed 240 ohms.
Also, what is your system voltage? Might want to measure that to see if it is an issue, too.
Is your alternator charging?
Doug
Teching In
Joined: May 2014
Posts: 10
Likes: 0
From: Bunkie, la
1984 chevy I've got a 1984 chevy silverado with a ls1 motor and a 4l60e trans. Truck does not stay running. I got good fuel pressure. Fuel pump and regulator is good also. If you cycle the key 3 times it runs fine. Could it be the computer is bad? Any suggestions.
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Verdad Gallardo TECH Fanatic
Joined: May 2010
Posts: 1,081
Likes: 8
From: Atlanta, Ga
Look for DTC's before you go any further. There are a number of things that can cause the problem. I faced a similar problem recently, it would also cause stalling when hot. I finally traced it to the cam position sensor. The only time the DTC would show was when the engine finally stalled running at temperature. It created hard start/no start condition similar to your issue.
On The Tree
Joined: Mar 2012
Posts: 131
Likes: 1
My car has done the same thing recently. The only thing that seems to consistent is I had removed the battery for long periods of time. Don't know if this helps or not, but if mine does it again I'll check for more codes than usual. ECM not reprogramed yet.
