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Unstable TPS voltage


gropula

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Hello, I bought Rapidbike Racing for my bike to fix fueling and high fuel consumption issues. It really did help, bike is faster, more responsive and consumes less fuel. The problem I'm having is that TP sensor minimum voltage (0% throttle) is unstable. That means I can't get low throttle fueling (0-5-10%) right, as I can't set the minimum and maximum voltage correctly. With the engine off and ignition on I get one reading, turn on the headlights the reading is different, turn on the engine different again. Fan starts spinning when hot - different again. What could be causing this? Is that related to 5V rail voltage stability? Is the reg/rec to blame, I still have the stock one.

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The TPS power is fed from the 5v Reference voltage from the ECM and this should be rock solid. Check this voltage and make sure it is stable, and is the same value at both ECM and TPS.

 

TPS info goes through two conectors before it gets to the ECM. So best to have a very close check of these connections making sure they are clean and good from TPS to ECM.

 

The other important thing is to make sure the signal ground wire Green/Orange measures zero ohms back to the Battery negative terminal.

 

You can easily measure the R/R output voltage checks. Any doubts you could run the engine for a short period with the R/R disconnected for testing of the TPS signal.

 

Good luck.

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I did the checkup by the manual.

 

1.) TP sensor connection inspection:

MIL not blinking - pass

 

2) TP sensor input voltage inspection:

Voltage from TPS pink wire to ground is 5.03, if I turn on the headlights it's 5.15, and if I turn on the position lights it's 5.04. - fail

 

3) TP sensor power input line voltage inspection

Voltage stable at 5.03V, with or without headlights or any other load. - pass

 

4) TP sensor line short circuit inspection:

 - pass

 

5) TP sensor input line inspection: Check for continuity between the test harness terminal and the TP sensor connector terminal. Connection: pink - A16:

 - fail

I did this test by back probing the ECU with a wire and then connecting the multimeter to it and pink. There was no continuity. It could be that my back probing wasn't successful, but I think that I did it right because the next test required back probing two pins at the ECU and I was able to do that. 

 

6.) TP sensor Voltage at ECM

-pass

 

Voltage is within spec and readings are the same with or without additional load on the battery. Tested by back probing the ECU.

 

By Grum's recommendation:

 

I tested the 5v rail at the ECU - it was 5.03 and stable with or without load on the battery

 

I tested if the signal ground wire Green/Orange measures zero ohms back to the Battery negative terminal - it does not. It measures 1.1 ohm with no load on the battery, 14.2 ohm with position lights on and 88.0 ohm when headlights are on.

 

The ECU gets the correct reading but rapid bike gets a wrong reading, the more load I put on the battery the worse the error gets. Full beams give me 4% throttle reading...

 

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Test 2 - Is the 5v VCC at the TPS connector and this should be 4.75 to 5.25. Was meter black lead on battery negative? Important thing is that 5v is stable relative to Green/Orange signal ground as in Test 3. Might pay to check both ECM connectors that all pins and sockets are clean and good.

 

Test 5 - Agree but it would be good to know you have proper continuity of the TPS signal wire at the ECM A16 to the same wire at the TPS connector, being the wiper of the TPS potentiometer.

 

Bottom line is to check each of the three TPS wires for continuity from its connector back up to the ECM. (Power off of course!)

 

6 hours ago, gropula said:

I tested if the signal ground wire Green/Orange measures zero ohms back to the Battery negative terminal - it does not. It measures 1.1 ohm with no load on the battery, 14.2 ohm with position lights on and 88.0 ohm when headlights are on.

1.1 ohms to ground on the Green/Orange wire is probably O.K.

You shouldn't ever be measuring Ohms with power on, you could damage your meter! So forget those readings with lights on.

 

With everything fully connected and your meter set to low DC Volts. Turn power on, now with meter black lead to the battery negative and the red lead probing the Green/Orange (signal ground) wire at the back of the TPS. If you measure voltage and it varies from idle to WOT then the Ground is not good. There should never be Voltage on a Ground wire - With Respect to the Negative Battery Terminal.

 

Have you confirmed all connections, Power and Grounds are good for the Rapidbike unit?

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  • 3 months later...

Sorry for a very late reply. The bike was rideable so I didn't want to have down time during riding season. I was afraid it might take a long time to fix or I might have to give up and take it to the shop thus missing out on nice weather. The problem was in the bad ground as grum expected. Turning on the headlights or high beams applied voltage to the ground wire of the front electrical system (yellow connector) as well as ground wire of all sensors (TPS, IAT, O2, MAP share common ground - green orange). This was causing the bike to use more fuel and behave wierd because of wrong fueling. I fixed the problem by soldering a piece of wire to the back of the yellow connector and running it directly to battery negative terminal. I didn't want to disassemble other stuff to find where the green wire from yellow connector usually grounds, as this is a simple fix that cannot hurt anything else. Now sensors have no voltage on the ground and work as they should. I reset the mapping of rapid bike as it had adjusted the fueling to compensate somewhat for wrong sensor readings. Now the bike is more responsive of course and it will improve with time as the auto tuner does it's thing. I expect the fuel efficiency to increase as well. I want to thank everyone for help, a great community this is.

40E01B27-4538-47FD-ACCF-036D56CA5142.jpeg

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That's something I have been doing to all my vehicles, bikes and cars. None of the bikes are fuel injected, but still found voltage on the grounds. A friend had a 98 or 99 VFR that when riding behind him always smelled rich. Mentioned to him, but he didn't seem too concerned. Now I'm thinking this may have been responsible.

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5 hours ago, gropula said:

Sorry for a very late reply. The bike was rideable so I didn't want to have down time during riding season. I was afraid it might take a long time to fix or I might have to give up and take it to the shop thus missing out on nice weather. The problem was in the bad ground as grum expected. Turning on the headlights or high beams applied voltage to the ground wire of the front electrical system (yellow connector) as well as ground wire of all sensors (TPS, IAT, O2, MAP share common ground - green orange). This was causing the bike to use more fuel and behave wierd because of wrong fueling. I fixed the problem by soldering a piece of wire to the back of the yellow connector and running it directly to battery negative terminal. I didn't want to disassemble other stuff to find where the green wire from yellow connector usually grounds, as this is a simple fix that cannot hurt anything else. Now sensors have no voltage on the ground and work as they should. I reset the mapping of rapid bike as it had adjusted the fueling to compensate somewhat for wrong sensor readings. Now the bike is more responsive of course and it will improve with time as the auto tuner does it's thing. I expect the fuel efficiency to increase as well. I want to thank everyone for help, a great community this is.

40E01B27-4538-47FD-ACCF-036D56CA5142.jpeg

Hi Gropula.

Great news you have it sorted and thanks for the feedback regards the issue and repair, your information helps us all. There seems to be a few variations with models and years as to where these Ground Blocks are located, they sure cause issues over time.

The pins look nice and clean I hope the sockets in the yellow block are too. A good coating of Ox-Gard on the pins/sockets would be ideal in this application.

Cheers:fing02:

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The pins looked good as well as sockets in the yellow connector. There was some minor corrosion which I sanded of with sand paper, that's why it's so shiny on the picture. There was a burnt connection in the big blue connector on the left side. The black-red wire (high beam positive) burnt the connector. I cut the wire on both sides, soldered an extension and put a new connector on that wire alone. Next thing to do is replace the reg/rec. I bought it two months ago, but I didn't want to install it before I solved this issue. It's not a good idea to add more variables while diagnosing issues. I have bought a series/parallel regulator from a reputable local source. It's called SPER regler, in Zagreb Croatia, so people from eastern Europe have a good alternative to Schindengen. Guy builds them himself for only 110€. I talked to other VFR owner that has it and says it's perfect. Sourcing a genuine Schindengen is tricky and very expensive here.

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