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TPS voltage unstable reading

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Good evening I whould like to ask if a ground or a 5 volt splice can affect a TPS reading? According to the cars service manual I have two 5V supply & 2 sensor grounds. One supply and ground is used only by the MAP sensor. The other supply goes to EGR and TPS and the ground is common for EGR,TPS,IAT,O2 sensor. I'm using a different TPS than the stock one cause I switched to ITBS. I can understand a minor fluctuation due to vibration but not a 20% change in voltage sudenly. I also noticed that the voltage after that started to drop slowly after that

What engine is this?

The engine is a B20/Vtec inside a Civic EG9 ferio, I have changed the TPS in order to match the ITBs. I was seeing some fluctuations before but they were minor (0.02-0.05 Volts)

Does your IAT value change at the same time? If it does, the problem is most likely on the ground side, as that's what your TPS and IAT share.

Can you do a 'sweep test' of your TPS and confirm that its resistance changes smoothly and repeatably over its entire range?

When you say EGR, is that an EGR position sensor, or the valve itself thats sharing the 5V supply?

Luckily for me, I was logging on my pc. What I noticed on the logs is that when this happens the EGR position sensor logs 0.02 volts. The IAT value on this looks constant at 38 degrees Celcius

I'm battling this problem for quite some time now and I have made about 10 'sweep tests' and every time everything looks ok every time.

Is there a possibility for the TPS to show errors due to high environmental humidity?

I was thinking of running separate wires for the TPS at the beginning.

The Time on the log that you can see the error is 223.030s, IAT is 38C, TPS 7, VSS 0, RPM 576.

The ITBs are mechanically actuated and I have already checked if they close properly.

Attached Files

I checked the resistance of the TPS installed on the car. The reading with the throttle at rest is 723 Ohms and at WOT 5.25 KiloOhms with the resistance increased gradually from idle to WOT.

As I'm a little bit curious I had a TPS from the original throttle body and checked also the resistance with min 406 Ohms and Max 5.44 KiloOhms

I found the datasheet of the TPS installed on the throttle bodies.

Yesterday when I was taking a reading I noticed that the pins inside the econoseal connector have a little play inside could this create an issue like this?

I started the car yesterday evening TPS was stuck at 20% and it was like this in the hole run of the car! I went for a ride and slowly decreased to 12% stayed like this until a switched off everything when I went later to start the car again it was stuck to 6%.

Attached Files

Good Morning/Evening depending on which part of the world you are guys.

I was thinking yesterday that my issue might be on the harness so I opted to check.

I disconnected the Colvern TPS and firstly I checked the voltage between the plug terminals.

3 readings were taken:

Terminals 1-2 gave 5 volts

Terminals 1-3 gave 4.78-4.79 volts

Terminals 2-3 gave a 0-volt reading

I took the plug and a length of an old harness I have and connected the factory TPS on the harness to check if I get any stable readings on the logger by hand. So far the factory TPS is giving stable readings. I'll have to build an adapter to fix the factory TPS on the ITBs to check if the Colvern TPS is giving the unstable readings.

By the way, do the all throttle position sensors have return springs or not?

I think this thread is going out of the typical wiring tackle!

I would like to thank everyone in advance for your help on matters like this!

No, not all TPS's have return springs. Your resistance readings make sense for your Colvern TPS, does it still have these measurements since you've had the problem with your TPS reading in the ECU being stuck at a certain value?

You mention that when your TPS reading glitches, your EGR reading is at 0.02V? Does it jump down to this level at the same time the TPS reading fluctuates? Or is it at a constant 0.02V? Just trying to get an idea if both readings are glitching, or just the TPS.

Econoseal connectors are not my favorite, but I've not had huge problems with them either. I'd swap it out for a 3 pin Deutsch DTM.

It is possible you've got a bung TPS!

Yes, the measurements are still showing the same results but the EGR doesn't show consistent fluctuation.

For example, I have readings with the TPS stuck at 14% and the EGR to 0.00v and the same TPS with the EGR 0.02v.

I will order a new TPS in order to check. Is it possible to switch from a resistive to hall effect?

Yes, most hall effect TPS's will take the 5v sensor supply and ground, so you should be able to swap to one without any wiring changes.

Hello from this part of the world Zac and I'm sorry to bring this topic up again but I noticed something today and I want the opinion of an expert on this! You asked in an earlier post if the readings from the IAT sensor change as I play with my throttle and my answer was that I see a constant reading on the IAT sensor! And I want to ask if it's possible for the reverse to happen as the IAT temp rises the TPS to give a smaller reading? I'm still waiting for my new TPS to arrive but I want to check everything just in case

It'd be far less likely, as your IAT sensor isn't directly powered, so a short between its signal wire and signal ground would result in you seeing 0V on your IAT input all the time, but should affect the sensor ground level. You can try heating it up with a heat gun (from a bit of a distance, don't melt it), and then cooling it off with compressed air to vary its temperature and see if you get any other odd effects.

I tried heating the IAT with the heatgun but no change at all! Anyway I will wait for my new TPS and If I see no change at all I will rewire all the sensors from the beginning! Any recommendation on a plug for a daily driver? The factory harness pass through a grommet from the firewall and I would like to upgrade from that!

I have good news guys the new TPS is on stage and rocks the universe as hard as I can press the throttle pedal! I avoided the rewiring!

Nice! Glad you got that sorted :-).

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