Resolved 1G TPS Circuit Fried? (Pic Attached)

[360glitch]

I'm still trying to tackle the dreaded idle surge. I tested the resistance of my TPS and everything seemed ok so the next step was to check the voltage on the pins of the harness side. With the key in the "on" position I measured a solid 5 volts on one of the three pins. On the other two I got nothing. Is this normal or do I have a short somewhere?

 

[spinz4]

With the key in the "on" position I measured a solid 5 volts on one of the three pins. On the other two I got nothing. Is this normal or do I have a short somewhere?

That's normal.

 

[andy4g63]

Just try and check the voltage:

Should be like 0.50V with the ign. ON and throttle closed and 4.95V and up with WOT.

 

[steve]

I'm still trying to tackle the dreaded idle surge. I tested the resistance of my TPS and everything seemed ok so the next step was to check the voltage on the pins of the harness side. With the key in the "on" position I measured a solid 5 volts on one of the three pins. On the other two I got nothing. Is this normal or do I have a short somewhere?

What were you expecting?

With the connector disconnected your going to see +5v on pin 1 and no voltage on pin 4 since it's ground. Pin 2 shouldn't have anything since it's the output of the sensor back to the ECU and pin 3 isn't connected on a 1G. On a 2G it will have a voltage since it's the IPS line from the ECU and has a pullup to 12v in the ECU.

The TPS has to be connected to see any voltage on pin 2. The difficulty then is accessing pin 2 while it's attached to the TPS. The dealer has a special adapter that connect between the harness and the TPS to allow measuring the voltage.

 

[360glitch]

What were you expecting?

With the connector disconnected your going to see +5v on pin 1 and no voltage on pin 4 since it's ground. Pin 2 shouldn't have anything since it's the output of the sensor back to the ECU and pin 3 isn't connected on a 1G. On a 2G it will have a voltage since it's the IPS line from the ECU and has a pullup to 12v in the ECU.

The TPS has to be connected to see any voltage on pin 2. The difficulty then is accessing pin 2 while it's attached to the TPS. The dealer has a special adapter that connect between the harness and the TPS to allow measuring the voltage.

Well that's definitely good news. I guess the wording in the manual confused me. So I just need to rig something up to temporarily connect the two that would allow me to measure voltage while they are connected? i am I just checking one of them or all of them?

 

[steve]

You have already checked the feed. You might want to verify the ground my measuring the resistance from pin 4 to the chassis.

I have two easy ways to measure the TPS output voltage when adjusting it to the factory spec of 0.5v at idle. My datalogger will tell me the output as either a percentage (want about 10% on a 1G) or voltage (want 0.5v).
My SAFC will display the measured voltage on the sensor check menu. The normal TPS display is scaled percentages based on the highest and lowest voltages it's seen, not absolute, so you have to use the sensor check menu.

If you don't have either you may find measuring at the ECU pins easier than making a harness extension. You need a helper then to adjust the TPS or a long set of leads.

 

[360glitch]

You have already checked the feed. You might want to verify the ground my measuring the resistance from pin 4 to the chassis.

I have two easy ways to measure the TPS output voltage when adjusting it to the factory spec of 0.5v at idle. My datalogger will tell me the output as either a percentage (want about 10%on a 1G) or voltage (want 0.5v).
My SAFC will display the measured voltage on the sensor check menu. The normal TPS display is scaled percentages based on the highest and lowest voltages it's seen, not absolute, so you have to use the sensor check menu.

If you don't have either you may find measuring at the ECU pins easier than making a harness extension. You need a helper then to adjust the TPS or a long set of leads.

Thanks for the info. When adjusting the TPS does the car need to be running or do you just mean with the throttle body closed?

 

[bluetlr2001]

Thanks for the info. When adjusting the TPS does the car need to be running or do you just mean with the throttle body closed?

No you dont need the car running just need to have the key on and have someone press and release your gas pedal while you adjust the tps.

 

[360glitch]

No you dont need the car running just need to have the key on and have someone press and release your gas pedal while you adjust the tps.

Awesome, thanks.

 

[steve]

and have someone press and release your gas pedal while you adjust the tps.

No, you set the voltage with the throttle closed. What it reads at WOT is a mechanical issue. If it's set correctly with the throttle closed then what it reads at WOT depends on how far the linkage actually opens the butterfly and not anything to do with the TPS setting. Within reason the ECU doesn't care what the actual WOT voltage is.

 

[360glitch]

No, you set the voltage with the throttle closed. What it reads at WOT is a mechanical issue. If it's set correctly with the throttle closed then what it reads at WOT depends on how far the linkage actually opens the butterfly and not anything to do with the TPS setting. Within reason the ECU doesn't care what the actual WOT voltage is.

Thanks for the extra information and clarification.

 

[bluetlr2001]

No, you set the voltage with the throttle closed. What it reads at WOT is a mechanical issue.

But I have read many times that you want the ECU to see as close to 5v as possible to know that it is WOT.

 

[steve]

But i have read many times that you want the ecu to see as close to 5v as possible to know that it is wot.

If you can point me to the ECU code where it looks for a specific value "as close to 5v as possible" to decide it's at WOT I'll be happy to change my statement.

Short of that you'll have to decide who to believe. While I haven't looked at every line of code in both the 1G and 2G ECU's, I've looked at/disassembled enough that I can be pretty confident in what I say.

In addition, if you understand the mechanics of how the TPS operates and read the factory adjustment procedures you will see that it has to work like this.

 

[talon187]

I don't mean to high jack someone else thread but I'm having a problem with my TPS as well.

When the car is at WOT I see 4.95 volts and when the cars at idle I see none. I've been seeing the check engine light ever since I changed back to my stock throttle body.

I took the TPS off and turned it by hand and if I do this the car leans out to 18.0 a/f or so. I'm guessing that the TPS is bad can someone confirm?

 

[bluetlr2001]

If you can point me to the ECU code where it looks for a specific value "as close to 5v as possible" to decide it's at WOT I'll be happy to change my statement.

Short of that you'll have to decide who to believe. While I haven't looked at every line of code in both the 1G and 2G ECU's, I've looked at/disassembled enough that I can be pretty confident in what I say.

In addition, if you understand the mechanics of how the TPS operates and read the factory adjustment procedures you will see that it has to work like this.

I believe you also i have just read that in some of the other threads. I know myself that you also want it to read 0.00 volts when the tps is fully closed. And the mechanics of the tps are just to let the ecu know what position the throttle is at.

 

[steve]

I know myself that you also want it to read 0.00 volts when the tps is fully closed.

No you don't, not even for a 2G.

The factory specifications are:

On a 1G, the TPS should be adjusted to read between 0.48v to 0.52v with the throttle closed.

On a 2G you adjust the TPS based on the switching point of the internal IPS when there is a 0.0177" feeler gauge between the pulley and throttle stop (the fixed SAS). The output voltage with the throttle closed should be between 0.40v and 1.0v. Anything over 4.5v at WOT is within spec.

If your using a datalogger on a 2G to monitor the voltage the value reported may be scaled making you think the output is 0v when it's really not.

DSMLink has it's own TPS code and behaves differently than stock.

And the mechanics of the tps are just to let the ecu know what position the throttle is at.

That's wasn't what I was getting at. The TPS is a variable resistor connected to a shaft. The output is proportional to the rotation of the shaft. Once the initial (throttle closed) setting is made there is no WOT adjustment. It is what it is, strictly based on how much the shaft rotates. The output is pretty much linear with the degrees of rotation.

Anyway, I think we have answered the posters question.