[RESOLVED] TPS Sensor Bad?

[jeremylee_7]

Hello, so I am getting a Throttle Position Switch CEL, i went and did a log with dsmlink and the tps stays at 0 and .4 volts. So i took off the hanress and checked the resistance at pins 1 &4 and 2 &4 and both were in spec (4500 ohms on 1 & 4, and 0-5k ohms on pin 2 & 4 as i hand rotate the throttle). So I checked the voltage at the tps pin at the ecu and it is getting .4 volts just like dsmlink says.

So I have low voltage coming from the tps but the resistance values are all good, so is my tps bad or is it more likely that i have bad wiring/ground?

Also, I checked the ecu harness sensor ground pins with voltmeter and both grounded ok.

 

[luv2rallye]

Bad sensor ground. TPS Sensor ground must ONLY be grounded through the ECU (pins 17 and 24) - not to engine or body ground (although the ECU will ground to this internally). This prevents ground loops and grounds that are at different voltage potentials. It's easy to check - just unplug the ECU. If TPS sensor ground (at TPS) has continuity to engine or body, it is being grounded elsewhere.

 

[jeremylee_7]

ok, when i tested the ground wires, pin 17 and 24, what i did was hook the pos lead of the multimeter to the const power at the ecu and neg lead to pin 17 and then 24 to see if it grounded ok,

I will test the tps sensor ground when i get back to the car latter, thanks!

 

[jeremylee_7]

Ok, when i checked continuity between the tps ground wire and grounding point on the body there was none (no beep, no reading, acted like i was not touching the multimeter to anything), although with ecu plug still off I touched pos side to battery and neg to tps ground and it read 12v, should it be doing that?

Also to test the ouput wire I hooked up 9v to pin 2 of tps harness and got the right voltage from wire at ecu with multimeter, and with plugging harness back into ecu i get 5v at tps power wire (but not with the harness disconnected).

So i do not seem to have continuity b/t the ground wire and the body, but i get 12v reading using multimeter to battery and tps ground (ecu harness disconnected), and the other two wires seem to be working correctly.

Just FYI, i currently have my buddies ecu in my possession and I get the same tps circuit cel with his ecu and my dsmlink chip, or my ecu and chip.

The car has to run for a minute or two and then the cel will come on and stay on (even after clearing code with dsmlink) and once the cel code comes on it starts idling around 1500 rpm. (also my fiav is blocked off).

 

[luv2rallye]

Ok, when i checked continuity between the tps ground wire and grounding point on the body there was none (no beep, no reading, acted like i was not touching the multimeter to anything),

good, that's how it should be with ecu plug off (with ecu plug on there should be continuity through the ECU - test this.)

although with ecu plug still off I touched pos side to battery and neg to tps ground and it read 12v, should it be doing that?

yes if your pos side of meter was put on battery positive. However that is a meaningless test as it is completing the circuit to ground through another device - probably the air flow sensor.

Also to test the ouput wire I hooked up 9v to pin 2 of tps harness and got the right voltage from wire at ecu with multimeter, and with plugging harness back into ecu i get 5v at tps power wire (but not with the harness disconnected).

That is correct if you mean by tps power wire it is tps pin 1.

So i do not seem to have continuity b/t the ground wire and the body, but i get 12v reading using multimeter to battery and tps ground (ecu harness disconnected), and the other two wires seem to be working correctly.

Everything sounds correct but make sure you have tps sensor ground continuity to body ground with ECU plug in

Just FYI, i currently have my buddies ecu in my possession and I get the same tps circuit cel with his ecu and my dsmlink chip, or my ecu and chip.

The car has to run for a minute or two and then the cel will come on and stay on (even after clearing code with dsmlink) and once the cel code comes on it starts idling around 1500 rpm. (also my fiav is blocked off).

I think your tps may be bad. I say this because I just noticed in your 1st post you said "(4500 ohms on 1 & 4, and 0-5k ohms on pin 2 & 4 as i hand rotate the throttle)". I couldn't find the 1 & 4 spec for a 1g (2g is 3.5-6.5k) but whatever it is, the 2 & 4 value can NEVER BE greater than it or it's bad! I suggest swapping tps with your friends if possible. Also re-measure 2 & 4. It should go smoothly between 0 and 4500 (it may be a little above 0 and a little below 4500) as you turn it all the way.
Another possibility is the tps sensor ground foil path is damaged inside the ECU (to body ground or to other ECU circuitry). Open up ECU and look for this and leaking capacitors.

The following is from "Troubleshooting fried ECU components" which you should read (at http://www.dsmtuners.com/forums/art...85-troubleshooting-fried-ecu-components.html):
"If you are getting a CEL, and the codes are sensor related but the sensors are OK, this is usually the problem.You can test this by checking for continuity between the main ground and sensor ground pins on the ECU.If there is no continuity, check the back of the ECUs PCB for a fried/broken trace.I don't have pics of this, but it should be fairly easy to spot.After checking for shorts to the sensor ground under the hood(and fixing above problems), you can just solder a jumper to restore the connection."

 

[jeremylee_7]

Same no reading for continuity on pin #4 with ecu plug disconnected, 0.00 reading with ecu plug connected, as it is supposed to be.

Tested the resistance on the tps again, 5.06k ohms on 2 & 4 and 4.90k ohms on 1 & 4; so yeah sounds like it is bad, I will go ahead and order one tomorrow (friends tps sensor is bad, so cant borrow his)

Thanks a lot for the help luv2rallye.

 

[luv2rallye]

Something still doesn't make sense. You checked tps with it disconnected right?

And you tested the correct pins right? The values are so close and in fact, they are exactly what I'd expect if you had the pins mixed up (5.06k on 1 and 4, 4.90k on 2 and 4 with it turned all the way). Check the pins wire colors again (wire on pin 1 is gray, pin 2 is green-white, pin 4 is green-black, 3 is missing). I think you either have them mixed up or one of us has a manual that is wrong (I'm looking at the DSM Backup Manual which is a copy of the 91 Laser/Talon Service Manual).

And you tested for smooth increasing/decreasing resistance between 2 & 4 and changing the other way between 1 & 2 right? All with no breaks while turning the shaft and resistance near 0 at one end and near max at the other?

I'd hate to see you buy a new one when that's not the problem. Another possibility is the tps connector isn't mating properly. Check if the pins are locked in place and fit together properly. Also check the ones on the ECU connectors.

A third possibility is there's no continuity of each wire to the ECU. Check for continuity tps pin 1 (gray) to ECU pin 23, tps pin 2 (green-white) to ECU pin 19, tps pin 4 (green-black) to ECU pins 17 and 24. And with ECU disconnected none of these should have continuity to ground (body).

 

[jeremylee_7]

Ok, i retested the tps and i got the same resistance values for 1&4(4.96) and 2&4(.77-5.07) and the resistance increases smoothly when i open the tb.

All three tps wires have no continuity when put at ground.

When i tested the continuity from tps harness to ecu harness they all had continuity with fluctuating resistance (different numbers in the range from 0 to 10k ohms).

 

[jeremylee_7]

I checked the resistance on pins 1 & 2 to the tps, it only goes up to 4.45k Ohms at closed (verses 5.06k ohms from pin 2 & 4)

 

[luv2rallye]

Ok, i retested the tps and i got the same resistance values for 1&4(4.96) and 2&4(.77-5.07) and the resistance increases smoothly when i open the tb.

ok, close enough. Perhaps the difference between 5.07k and 4.96k is some extra resistance in the sliders contact inside the pot. I doubt 110 ohms is going to make any difference (slight possibility but very unlikely - effect will be ECU pin 19 may be slightly below 5v instead of exactly 5v which I doubt is enough to have any effect).

All three tps wires have no continuity when put at ground.

good.

When i tested the continuity from tps harness to ecu harness they all had continuity with fluctuating resistance (different numbers in the range from 0 to 10k ohms).

What? The manual shows they all are direct wires! Which paths show what resistance?

 

[luv2rallye]

I checked the resistance on pins 1 & 2 to the tps, it only goes up to 4.45k Ohms at closed (verses 5.06k ohms from pin 2 & 4)

That's probably due to it being held slightly open by idle stop screw/tang. 4.45k should work though.

 

[Simadowna119]

if your getting the cel, just replace your TPS..i would replace it and move on being that they go for only 20 bucks instead of testing and worrying about it

 

[jeremylee_7]

What? The manual shows they all are direct wires! Which paths show what resistance?

I changed out my battery in my multimeter and got more consistent results on the direct wires (i checked all the values agian on the tps and they were the same). Going from tps 2 to ecu 19 and tps 4 to ecu 24&17 there is no continuity; when i go from tps 1 to ecu 23 (vfaq says maf power and fyi i have a translator) i get continuity for half a second and then it goes to none.

 

[luv2rallye]

Yes tps 1 is 5v power to it and the air flow sensor. I'm not familiar with a translator so if any of the tps wires go to it any resistance reading is possible (especially infinite). And if a tps cel code can be generated because of it, someone else who knows will have to help you. If a tps is only $20 as simadowna119 says, I agree at this point - just go buy one and try it.

 

[Kng Nothg]

I'm having this same issue. Where did you find the $20 TPS!?!

Is it fixed?

 

[wishnfor4g63T]

i've had this same problem on my car since day one. Only after figuring out that if this problem wasn't fixed i couldn't tune it. i've replaced my tps with another dsm tps that was "known" to be working. it didn't fix my problem.

my tps on the afc neo also reads like a .001-.004v when i look at the readout on either TPS i use

:-(

 

[jeremylee_7]

As far as i know replacing it fixed the problem, changed the tps and the dsmlink showed the proper values but waiting on one more part before I can take it for a drive to know for sure.

I got my tps off of dsmtuners classifieds for 25 bucks (i bought a couple of other items from the seller as well), there is an auction on ebay for tps for a 1g
1G DSM 4G63 Throttle Position Sensor TPS Turbo Eclipse:eBay Motors (item 400065197600 end time Sep-30-09 07:12:22 PDT)

Otherwise would just watch classifieds from dsmtuners and dsm trader.

Did you guys do the resistance test on your tps?

wishnfor4G63T, not much of a dsm scene out here, but i can ask my 2g friends if they have one to part with if you would like.

Ok so after i got another tps i connected it up and dsmlink read the signal correctly, but i could not start the car due to a scrambled memory board settings. Got a replacment back from dsmlink and now i got a tps cel agian. I am getting no ouptup from the tps and I am only getting a max of 4.6k ohms resistance b/t pins 2&4.

Do you think I just happened to have a tps on its last leg, or is my ecu or sensor ground killing it out.
FYI i had an ISC go out on me not too long before the first TPS died on me.

Ok, i discovered something that might be the problem.

There used to be a MAP sensor on the car, but the previous owner removed it, when they did they disconnected the power wire, but left the signal and the ground wire hooked up, when i traced the old map harness back the signal went to the egr of course and the ground went to....the tps sensor ground a ways into the harness. So since the old MAP harness was just hanging there, if it grounded out to the body would could that have caused all my tps problems, maybee even killed the replacment one in my car now.

 

[jeremylee_7]

UPDATE
I checked the TPS with multimeter and results are as follows:
Pin 1 & 4 = 4.68k ohms
Pin 2 & 4 = .9k - 4.63k ohms as i rotate the throttle

With ecu disconnected I get continuity (19k ohms) from tps pin 1 to ground, as well as from ecu pin 24/17 to ground.

When I tested the car after running a minute or two the car stays at 1700-2000 rpms at idle

Seems like it is not grounding correctly.
Should i just run a new sensor ground wire from the tps to ecu pin 24 or is there some other fix i should do?

 

[steve]

UPDATE
I checked the TPS with multimeter and results are as follows:
Pin 1 & 4 = 4.68k ohms
Pin 2 & 4 = .9k - 4.63k ohms as i rotate the throttle

With ecu disconnected I get continuity (19k ohms) from tps pin 1 to ground, as well as from ecu pin 24/17 to ground.

When I tested the car after running a minute or two the car stays at 1700-2000 rpms at idle

Seems like it is not grounding correctly.
Should i just run a new sensor ground wire from the tps to ecu pin 24 or is there some other fix i should do?

That doesn't sound right.

With the ECU disconnected you should be measuring infinite resistance between the TPS connector pins or the ECU connector and ground. It should read the same as when you don't have the meters probes touching. What we call an open circuit.

I consider continuity less than 1 ohm but technically it means that is some connection between the two points even if it's a high resistance connection. Usually what we want to know is that there is a good connection between the two points and the closer to a short (0 ohms) the better.

So with the ECU disconnected from the harness there should be no connection from any of the wires in that harness to ground or power for that matter. The ECU provides the connection to ground on pin 4 and to +5v sensor power on pin 1.

Let me make sure I understand what your trying to solve. You had a TPS CEL and DSMLink said that the TPS% was 0 and the TPSRaw voltage was 0.4v.

That would throw a CEL since the TPS voltage at idle should be around 0.5v and DSMLink's code prefers 0.6 something. So besides a bad TPS, misadjustment and a non-functioning IPS can also cause the TPS CEL.

 

[jeremylee_7]

Yes that is correct steve.

I just checked and with the ecu disconnected, tps pin 4 will ground and show 12v with the pos at battery and neg at tps pin 4 of multimeter.

To fix this problem can I run my own wire from tps pin 4 to ecu pin 24 (cutting and taping off the factory harness of course), or what do I need to do?

 

[jeremylee_7]

Ok just figured some more out.

As I said i was getting resistance at tps pin 4 to ground, and 12v from pos at battery and neg at tps pin 4.

Well when i unpluged the maf plug from my translator everything read the way it was supposed to.

Does anyone know enough about the translator to know if that behavior is actually normal?

 

[steve]

My mistake. The MAF and a MAFT have circuitry in them and are connected to the same pins for sensor power and ground but it shouldn't be providing a ground when connected.

What made you decide to measure between the positive terminal and the harness?

 

[jeremylee_7]

Just figured if the sensor ground plug was in fact grounding out some place else then i should see voltage b/t the battery and tps sensor ground wire.

I am also a little dumb founded how it could ground because the sensor ground wire should be its only source to ground at.

Now the MAFT pink wires are 12v according to the manual , but yet it grounds through the factory maf cable to the green/black wire that is the sensor ground, so is the maft only grounding out 5v or is it wrong for it to be being hooked up to that wire?

 

[jeremylee_7]

Ok this is even weirder, i leave the maft plug hooked up to the stock 1g maf harness, but disconnect the gm maf harness and everything behaves like it is supposed to (0v and no continuity).

 

[jeremylee_7]

Apparently someone tried to tap into the ground wire for something (map maybee) in the plastic covered bundle on the intake mani and I found the wire half broken apart, fixed that and everything worked fine agian.