I tested the tps sensor.
Ground to signal return = .7 ohms
koeo ground to reference volts = 5.05 volts
koeo ground to tp signal I get less then a volt but when I move the throttle it doesn't change so I replaced the tps twice and get the same reading from both new sensors. Both were bought from advanced auto bwd brand. Whats the like of two sensors being bad? Or am I missing something?
Truck is a 1994 4.9 e4od 310,000 miles

 

What do you see between signal return and TP signal?

SIG_RTN and GND should be the same level. Should be. As you see, though, on your truck they aren't.

Are you testing the sensors before you take them from the store? They should show a smoothly increasing resistance between the SIG_RTN and TP_SIG pins as you turn the element inside. If it doesn't, it's defective.

 

I just tested both the old and the new sensors the old has no movement the new has movement starts at .7ohms and goes to 3.9-4.1ohms

 

I'd check the new TPS again, and verify the range the meter is on. Chilton doesn't list the resistance; Haynes says it should be between 3000 and 4000 ohms at max.

 

You may want to read what is in this link below if you have not read it yet.

Fuel Injection Technical Library » Throttle Position Sensor (TPS)

/

 

Good information, Bill.

Four ohms as a reading for the new TPS jumped right out at me, Spyder, because with a five volt reference voltage applied to it it will dissipate more than six watts. The life span of what is, at best, a one-watt resistive element would be measured in seconds or minutes if it dissipates that much power. If it actually is reading 4000 ohms, lifespan would be measured in at least years. Since that is only a difference in range, not in the base reading, it would be an easy thing to overlook. (I cut my teeth on a Simpson 260, with multiple possible ranges for each needle position. I still mistake the range on occasion, especially if I am tired or harried.)

 

I check one a few minutes ago with a Simpson 260 and got around 3.8K ohms.

 

The reading I am getting is 3900 -4100 ohms sorry about the mix up. I also took the main bulk head connector and found some corrosion there also some at the pcm connector and pins. I removed the pcm took a part and found T main capacitors fried at the board.

 

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