ECMlink TPS Sensor Voltage Problem

[McDizle]

I've been searching all day and I can not seem to find the same problem I have. Anyway, I did an awd & 5 speed swap on my spyder. it ran good beforehand. Got it going afterwards and it was fine than i had a spark plug wire go wrong and that caused some misfiring but now it's all fixed. Than I wanted to fine tune my car, specifically idle. So i performed a boost leak test found a large leak at the throttle body shaft seals. Pulled the throttle body, changed the seals and put it all back together. Took the car out and it was fine. Got gas, turned it back on and had a problem. It ended up being the tps was not reading properly. It would stay at 0% for a while and the car would bounce between 1200 to 1700 rpm. I adjusted at the gas station but i could only get 58% throttle no matter how i adjust the tps. But that allowed me to get it home, anyway messed with it all day and i still can only get 58% throttle and about 3.2 volts. If i pull the tps off the throttle body and and play with it I can get like 3.8 volts and 70% throttle rotating the tps all the way. I checked resistance and it met specifications. I than checked volts. The green and yellow wire has about 4.9 volts but it seems as if that voltage isnt completely getting to the ecu. Hopefully someone can help I'm so clueless I feel like I've tried everything

 

[92AWDHX40]

Could be a short somewhere in the harness.

 

[McDizle]

Could be a short somewhere in the harness.

That's what I was thinking. Anyone know the path the TPS harness wires take through the firewall and to the ECU?

 

[luv2rallye]

The green and yellow wire has about 4.9 volts but it seems as if that voltage isnt completely getting to the ecu.

The ECU (pin 81) provides that 5V to the TPS, not the other way around.

Check your Idle Position Switch (TP switch): http://www.dsmtuners.com/threads/bad-tps-again.255885/#post-151940336. Read post 14 first, then 13.

 

[McDizle]

The ECU (pin 81) provides that 5V to the TPS, not the other way around.

Check your Idle Position Switch (TP switch): http://www.dsmtuners.com/threads/bad-tps-again.255885/#post-151940336. Read post 14 first, then 13.

I thought the green and yellow wire provides a constant 5v and the brown and red wire goes to the ECU and as the throttle open the voltage increases on the brown and red wire, thus telling the ECU the throttle position? Also its hard to explain but if you remove the TPS sensor and rotate the assembly inside by hand to WOT it will only read about 3.2-3.4 volts in ECMLINK and thats with using TPSAdjust. That's why I dont think it's a mechanical problem but more of an electrical problem

 

[edged1g]

I thought the green and yellow wire provides a constant 5v and the brown and red wire goes to the ECU and as the throttle open the voltage increases on the brown and red wire, thus telling the ECU the throttle position? Also its hard to explain but if you remove the TPS sensor and rotate the assembly inside by hand to WOT it will only read about 3.2-3.4 volts in ECMLINK and thats with using TPSAdjust. That's why I dont think it's a mechanical problem but more of an electrical problem

That's right but the phrasing is confusing. The green and yellow wire doesn't "provide" the voltage. The ECU provides it. There is 5V on the wire, and the other wire is the signal wire. There is something preventing the signal from reaching the ECU. You need to probe the signal wire at the sensor and see what the voltage is. If it matches what ECMlink is showing, suspect a faulty sensor. If it doesn't match, suspect the wiring.

 

[McDizle]

That's right but the phrasing is confusing. The green and yellow wire doesn't "provide" the voltage. The ECU provides it. There is 5V on the wire, and the other wire is the signal wire. There is something preventing the signal from reaching the ECU. You need to probe the signal wire at the sensor and see what the voltage is. If it matches what ECMlink is showing, suspect a faulty sensor. If it doesn't match, suspect the wiring.

Just checked it. It was .23 with the throttle closed or at idle and 1.49 at WOT so than it confirms it's a wiring problem as that's what i got in ECMLink without using TPSAdjust. Now to find the wiring problem. Anyone know the path those wires take to the ECU? Like where under the dash. Don't have time to look just this second just curious if anyone knew. Thanks a lot so far everyone

 

[edged1g]

Just checked it. It was .23 with the throttle closed or at idle and 1.49 at WOT so than it confirms it's a wiring problem as that's what i got in ECMLink without using TPSAdjust.

Can you clarify this? What is "it"? What was the voltage at the sensor(backprobing) compared to the reading in ECMLink? BTW, you can do this with the engine not running.

Voltage at sensor:
Voltage ECMLink reads:

 

[McDizle]

Can you clarify this? What is "it"? What was the voltage at the sensor(backprobing) compared to the reading in ECMLink? BTW, you can do this with the engine not running.

Voltage at sensor:
Voltage ECMLink reads:

Yeah I'm doing it with the car off. Sorry if I wasn't clear. Ok just retested everything. I turned TPSAdjust off in ECMLink and these are the readings

With throttle plate closed
Voltage at sensor: .23v
Voltage ECMLink reads:.18v

WOT
Voltage at sensor: 1.49v
Voltage ECMLink reads: 1.45v

Perhaps it is the sensor itself? I tried 2 of them with the same exact results

 

[edged1g]

Those results indicate to me that the wiring is OK and something else is going on. I'm not a 2G guy, so I can't tell you 100% but it seems that there should be a higher voltage at the ECU at WOT. In your OP you said you could get 3.8 volts. That doesn't work anymore? Also, what were the resistance numbers?

 

[92AWDHX40]

Did you test the sensor itself with a ohm volt meter, also the issue could be within the sensor.

 

[McDizle]

Those results indicate to me that the wiring is OK and something else is going on. I'm not a 2G guy, so I can't tell you 100% but it seems that there should be a higher voltage at the ECU at WOT. In your OP you said you could get 3.8 volts. That doesn't work anymore? Also, what were the resistance numbers?

The 3.8 volts was in ECMLink with TPSAdjust on. That was only reachable with:
TPS Offset: 7
TPS Scale: 199%

Did you test the sensor itself with a ohm volt meter, also the issue could be within the sensor.

I picked up a 3rd and brand new TPS on my way home and tested all 3 with all 3 having similar values both on and off the car.
Resistance between the original TPS: (The other 2 are almost perfectly identical)
Terminal 1&4: 4.89k ohms
Terminal 2&4 Closed: .8k ohms
Terminal 2&4 Open: 4.93k ohms

With the brand new TPS ON the car the voltage was
With throttle plate closed : .43v
With throttle plate open (WOT): 1.55v

 

[McDizle]

Just checked the voltage on the green/yellow wire. The ECU is only providing 1.5v why would that be? Something wrong with the ECU maybe?

 

[92AWDHX40]

Hey it could be a issue with the ecm send to ecmlink they work really fast.

 

[McDizle]

I talked to Thomas at ECMLink and he doesn't believe it'd be the ECU's 5v because if it was I'd be having a lot of other problems. The MAF, MDP, IAT etc. all use that 5v source. Still stumped, I may still send it in but I'll play around with it some more before I do that. Any other ideas?

 

[McDizle]

Found out it was one of the wires. Going to properly fix it tomorrow but played with it today and it was running and idling good. Thanks for all the help guys

 

[McDizle]

Still been struggling with a voltage issue. Finally decided to send out the ECU since i was getting 4.04v on the green/yellow wire about an 2 inches from the ECU. The guys over at ecmlink did several tests and everything was functioning properly so I had them send it back to me. Got it today and hooked it up and same thing 4.04v volts on the green/yellow wire. I have already taken the whole engine bay harness apart and checked for any damaged wires and found none so I checked under the dash. Nothing damaged, so I figured if i disconnected the the green/yellow sensor wires 1 at a time and test it I would find the damaged wire or at least the wire that is causing me all this grief. I checked all 3 green/yellows and got the same 4.04v over and over. So i figured I'd try the ground wires. Once again 1 by 1 I disconnected them and tested for voltage. On my second try I finally got 4.49-4.55v on the green/yellow wires WITH the ground disconnected! I traced the wire back to its sensor and it goes to the MAF. I tried swapping another MAF on and got the same results 4.04v. I tried wiring in another MAF plug and got about 4.30v on the green/yellow wires WITH the ground disconnected. I finally pulled the wire through the firewall and checked the whole wire and found nothing wrong with it. I'm very stumped at this point. If anyone has any ideas please feel free to throw them out there. Thanks guys

 

[luv2rallye]

A possibility is your TPS sensor ground (black wire) is miss wired, open, or shorted to chassis ground at a point other than through the ECU pin 92 (example: through another sensor like the O2). Signal ground is NOT the same as chassis ground (even though they may be connected together inside the ECU)!

On a 2g (but not 1g) ECU pin 92 (note: this pin is incorrectly labeled Ignition switch on some 2g ECU pinout diagrams) goes to the signal grounds of the following engine sensors: manifold diff pressure, engine coolant temp, front O2, rear O2, TPS, volume air flow (MAF), and on the 98 & 99 fuel tank diff pressure. Pin 92 is grounded inside the ECU but all these sensors signal grounds must NOT be grounded anywhere but through pin 92 to avoid electrical noise and ground loops from affecting the sensors differential signals and to guarantee that the sensor's ground is at the exact same voltage potential as the ECU ground (which it might not be with large current flowing through any other ground). Some people and even some mechanics, don't know/realize this and they mistakenly connect signal ground to the engine (as in a 1g). A typical example is when replacing the front O2 sensor and the harness connector/wires are damaged and need replacing. Connecting the O2 signal ground to the engine/chassis (or even battery negative) can cause misleading and noisy signals to the ECU causing the ECU to run the engine poorly. And if it is still also connected to the original harness signal ground wire, then all of the above engine sensors will also have that problem.

To test sensor grounds, unplug the ECU. Now check for continuity from the TPS black wire to chassis ground. It should have NO continuity (should get infinite or very high resistance). If there is continuity, then one of the other above listed sensors has their sensor ground improperly connected to chassis ground (you can find which by unplugging them one by one) or there is a short to chassis ground.

Another possibility is a blown sensor ground inside the ECU: See under "details" and the picture here: http://www.dsmlink.com/wiki/blownsensorground.

 

[McDizle]

To test sensor grounds, unplug the ECU. Now check for continuity from the TPS black wire to chassis ground. It should have NO continuity (should get infinite or very high resistance). If there is continuity, then one of the other above listed sensors has their sensor ground improperly connected to chassis ground (you can find which by unplugging them one by one) or there is a short to chassis ground.

Another possibility is a blown sensor ground inside the ECU: See under "details" and the picture here: http://www.dsmlink.com/wiki/blownsensorground.

Very informative thank you luv2rallye! I already had the ECU checked out by ECMLink and it checked out good. I'll definitely try checking the ground today with your method and get back to you with results!