TPS check for LT-1
Thread Starter
Instructor
Joined: Jul 2004
Posts: 130
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From: Naples FL
TPS check for LT-1
I am checking the TPS voltage on my '92 LT-1 using the two "top" wires i.e. blue and black. The stationary voltage is .655 volts which I believe is a little high. However, at WOT the voltage is only 4.12 volts not the 5 as per spec. There also appears to be a very low spot as you get near WOT. Would this indicate the TPS is bad.
Race Director
Joined: May 2001
Posts: 14,165
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A scan tool would be a big help. The LT1 TPS "self zeros" as long as it is within a certain range when you turn the key on. Unfortunately I do not remember what that range is. It then takes that zero point and calibrates itself ot register from 0 to 100% A scan tool will tell you more than just the voltage, it will tell you how the ECM is interpretting that voltage. It would allow you to watch and see if the ECM really does interpret that drop as a decrease in throttle position, which it probably does. If this is the case I would certainly replace it.
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
You don't need to replace it, the TPS is well with in Spec. I will look it up tonight and post the exact specs for you but I am 90% on the fact it with in tolerance and you will be hard pressed to find one that actualy puts out 5.0 VDC on a LT1
Race Director
Joined: May 2001
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True, mine never gets to 5V and it still registers as 100% However, if there is a voltage drop somewhere in there while he's still opening the throttle it could indicate some corrosion or something. Imagine if the computer saw 25% throttle while you've really got it open to 75% Probably won't damage anything, but it's not gonna be real pleasant to drive.
I'd do a little more testing before I replaced it, but it would certainly be suspect.
I'd do a little more testing before I replaced it, but it would certainly be suspect.
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Originally Posted by Nathan Plemons
True, mine never gets to 5V and it still registers as 100% However, if there is a voltage drop somewhere in there while he's still opening the throttle it could indicate some corrosion or something. Imagine if the computer saw 25% throttle while you've really got it open to 75% Probably won't damage anything, but it's not gonna be real pleasant to drive.
I'd do a little more testing before I replaced it, but it would certainly be suspect.
I'd do a little more testing before I replaced it, but it would certainly be suspect.
That is corrcet but you realy need a data logging software to check it unless it is throwing a code. I just remember a prety wide range for both idle and WOT for the LT1 TPS sensor. I know mine is working correctly because I can see both 0% TPS (.43VDC) and 100% (4.73). This is looking at some old logs I have at work.
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Thread Starter
Instructor
Joined: Jul 2004
Posts: 130
Likes: 0
From: Naples FL
Both my '86 and '87 L-98s had reading that were very close to what accepted as correct about .475 and just under 5 at the high end. The numbers that I got this morning were way off from these so I was concerned. The volt meter is the same one used previously. Any recommendations for code reading, software, etc. for an LT-1.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Datamaster does a good job. The cable is the expensive part but you should be able to get a demo version of the software which will tell you what you need to know.
If you have any friends at any local dealerships they should be able to check it out for you with a Tech II scanner.
If you have any friends at any local dealerships they should be able to check it out for you with a Tech II scanner.
