NicHoza

Hi everyone. When I bought my truck 8 months ago or so, the throttle position sensor was unplugged. It runs great, but I recently decided to try to get the throttle position sensor to work in the hopes of perhaps getting some better power or maybe better gas mileage.

I have two throttle position sensors, and I have tested them both with a multimeter, and each of them seems to work great through the entire range of motion (no dead spots). However, I get the same bad behavior when I plug in either of them, which is that the engine will not rev past ~2800 RPMs.

These are the only possibilities I can think of for this behavior:

1) They are the wrong sensors. This doesn't seem likely since they pass the tests and are in the ranges given here: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

2) My wiring harness is somehow bad, and plugging in the good sensor is providing bad signals to the ECU

Any other ideas? I couldn't find any posts on this forum addressing this particular problem, although there are lots of TPS related issues. Maybe it's not worth it. I would love a couple extra MPGs though. Not even sure that's a possible benefit. Any ideas or help is much appreciated!

Leviticus6432

Does it throw any codes when plugged in? I would assume you have a code thrown with it unplugged.

Leviticus6432

There is a chance the sensor isn't getting the correct refrence voltage from the ecu (prob 5 volts could be 12) I would look up a wiring diagram, figure out which wire is refrence, and test it with a multimeter... The reason it might work fine with it unplugged is that the ecu could be running in a sort of fail safe mode without the sensor plugged in, and when you plug it in it turns off the fail safe and actually reads the sensor (which is giving the ecu the incorrect reading)

yotaman85

It could be when you connect the TPS it actually adjust timeing causing a knock, and in return tripping knock sensor stoping the rpm from riasing.

Just a guess though...

NicHoza

I got diagnostic codes 7 & 11 with the TPS unplugged. Then I plugged in the TPS and now I just get a diagnostic code #7, which, according to http://www.4crawler.com/4x4/CheapTri...html#Early22RE is an "Open or shorted Throttle Position Sensor (TPS) circuit". This was the first time I have ever checked the diagnostic code. Is there any chance that this is an old code from before I plugged in the TPS? I ran the engine again and it was still giving me code 7 after that. No other codes. I revved it, causing the problem to occur a few times at 2800 RPMs, but still no other codes. This suggests that it is not a knock problem, correct?

I checked the TPS reference voltage, and it is at 5.00V. I did not check the other two wires (there are four total), so perhaps one or both of those two is open or shorted?

NicHoza

I checked the other two wires, and they both have continuity to the ECU on the 18-pin connector, as this diagram says they should:

http://www.well.com/~mosk/Images/22RTE_EFI.pdf

The VTA connector on the TPS had continuity with a light blue wire, as the diagram says it should. However.... the IDL connector had continuity with a solid black wire immediately next to a black and white wire. The diagram says that the IDL connector should be connected to a black and white wire (not a solid black wire).

I'm guessing the color discrepancy is due to colors changing in different years. Another diagram:

http://lakebox.dnsalias.com/photos/1...CCSdiagram.jpg

This diagram agrees with the pin numbers, but disagrees with some colors. It also shows the position of the pin numbers on the connector. Looks like my TPS is connected to the ECU correctly on all four pins, and receiving the reference voltage of 5V. Getting diagnostic code 7. I don't know what's wrong!

jonnydclark

Probably completely irrelevant but...

I had a 2003 Tacoma 3.4 that was hit hard up the middle of the front (PO hit a pole). It wouldn't rev past 3,500 rpm and the check engine light would flash when I tried. It sounded like it was starving for fuel or hitting the rev limiter. I took it to the stealership and told them it had been hit in the front before I fixed it. 3 days later they figured out that the crank position sensor was a little cockeyed.

What happens when it hits 2,800 rpm? If it has similar behavior to mine you might look for crank shaft or other rpm sensors and test them.

NicHoza

Well. I figured it out. Thanks for your help everyone, although in the end it just turned out to be a very dumb mistake on my part. I would have realized this if I had tried to adjust the TPS, but I was saving that for later. Turned out the behavior was the same with the TPS plugged in and dangling (rather than attached to the throttle body). I finally figured out that I had simply plugged it in to the throttle body wrong -- the rotating part was not rotating, because the prongs were on the wrong side of the mating part. How embarrassing.

Well, now I have an extra TPS which I have tested with a multimeter and verified that the resistance values are correct, with no dead spots. Anyone want a cheap TPS? $50 and it's yours. Part number 89452-28010.

jonnydclark

Don't worry, we all make mistakes, learn and move on. What I hate is making the same mistake twice.

I ended up with 2 extra TPS and one extra throttle motor before i got my Lexus GS300 to quit going into limp mode.