have trouble codes
Fleet Owner
Joined: Aug 2005
Posts: 23,667
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From: Easton,Ks
The egr sensor is from 0.50 volts to about 4.4 volts so it may think it is OK also.
You are the one reporting the bad voltages so until you get 5.0 volts between the VREF and SIG GND you are going to have problems.
Also I would not bank too much on the codes from a computer that is not putting out the right VREF voltage.
Posting Guru
Joined: Jun 2002
Posts: 2,091
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From: Suffolk, VA USA
Signal return sends the residual power not used by the sensor back to ground. If you have 5 volts going into a sensor, and the sensor needs to send 3.75 volts to the computer as the sensor reading, the other 1.25 volts has to go somewhere. Thats where signal return comes in. It takes all the residual power not used by the sensors and disposes of it. The numbers you want to concern yourself with are having 5 volts in to the sensors, and a sensor reading within the specified range.
Lead Driver
Joined: Nov 2002
Posts: 9,557
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From: Concord, NC
If you have 5 volts going into a sensor, and the sensor needs to send 3.75 volts to the computer as the sensor reading, the other 1.25 volts has to go somewhere. Thats where signal return comes in. It takes all the residual power not used by the sensors and disposes of it.
Posting Guru
Joined: Jun 2002
Posts: 2,091
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From: Suffolk, VA USA
Fleet Owner
Joined: Aug 2005
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Likes: 301
From: Easton,Ks
It is a voltage divider with 5 volts at one end and zero volts at the other.
You have a movable wiper that moves along the resistant part and is hooked to the information wire going back to the computer.
Along this resistant part the voltage is variable from one end to the other, 0 to 5 volts DC.
Where ever the wiper touches the resistant part this is the voltage level it sends back.
You do not send voltage anywhere. Only its potential. The only thing that is sent along a wire is current.
So you do not send any voltage back on the SIG RET wire. It is at ZERO volts.
Posting Guru
Joined: Jun 2002
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From: Suffolk, VA USA
Bill...not trying to argue, and I'm certainly not claiming to be an expert...all I know is that if you disconnect a ground wire and put a voltmeter in between it and the ground point you will get a voltage reading. Signal return connects to ground. That voltage would indeed be potential until it reaches a ground source and completes the circuit. I'd be looking for a weak or missing ground connection, probably off pins 40 or 60, and rule that out before anything else.
Fleet Owner
Joined: Aug 2005
Posts: 23,667
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From: Easton,Ks
I am not trying to argue either but saying the way it works and that it is stated wrong on that web site.
A bad ground would be putting another resister in series with the resistant part of the TPS.
Then you would be reading the voltage drop of the bad ground if you taking the reading at the SIG RET wire of the TSP. If it were and open ground you would read 5 volts at the SIG RET wire of the TSP.
Until he reads ZERO volts at the GND RET (SIG RET) at all three sensors he will have a problem.
It may be a bad connection at the computer plug (pins pushed in) or a bad ground at G101 (on the fender by the battery).
The computer itself would not cause a voltage reading on the ground wires.
A bad ground would be putting another resister in series with the resistant part of the TPS.
Then you would be reading the voltage drop of the bad ground if you taking the reading at the SIG RET wire of the TSP. If it were and open ground you would read 5 volts at the SIG RET wire of the TSP.
Until he reads ZERO volts at the GND RET (SIG RET) at all three sensors he will have a problem.
It may be a bad connection at the computer plug (pins pushed in) or a bad ground at G101 (on the fender by the battery).
The computer itself would not cause a voltage reading on the ground wires.
Posting Guru
Joined: Jun 2002
Posts: 2,091
Likes: 3
From: Suffolk, VA USA
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