Replaced TPS Sensor - still get .15 volts ???

90topdown · Dec 6, 2008

Trying to adjust my TPS sensor as I read that it should be around .7 to .9 volts.

Mine read .15 volts and I had a code 63 (low TPS voltage) so I replaced it with a brand new Ford TPS sensor and the new one reads .15 volts.

Here is what I am getting:

.15v between green and black wires on TPS KOEO

4.97 volts on the orange TPS wire on both side of the connector - KOEO

Pulling the EGR and MAF connectors made no difference - still got .15 volts

Checked the resistance between the black TPS wire and the neg batt post- got .05 ohms. so I assume that the ground is OK.

Any ideas??

hotcobra03 · Dec 6, 2008

Yea lets start with codes? What were all the codes? Was 23,53 or 73 present?

stang&2Birds · Dec 6, 2008

So, you need to try a few things to find the problem.
1) Key On Engine Off

2) See if the output voltage (orange wire) changes as you move the throttle to full.
You should see the output go past 4.5v at full throttle.
Again, this is with the Engine Off!

3) If the voltage changes, then you may not have the TPS on correctly, or you have some POS incorrect adjusted and manufactured TB.

4) If the voltage does not change:
Remove the TPS from the TB.
Move the slot by hand.
Notice the output voltage if it changes.
If it changes, you didn't have the TPS on correctly,

If the output voltage does not change, you have much bigger problems - a short somewhere on that wire. It may be on that wire, or it mat be in the EEC.

If you have a short, then you must cut wires to find the short. However, after you cut the wire, you MUST solder the wire and use heat shrink tubing on any wire that is outside the body. If you cut the wire near the EEC (which is best but a pain and you run the risk of cutting the wrong wire), you coukd then just crimp that wire and put heat shrink over it. I suggest using a light coating of dielectric grease on the wire before the crimp. That way, if you get a dash/window leak (thankfully not that common in Stangs), or a wet floors, then that light coating of dielectric grease helps to prevent corrosion. I'm taking about a very light coating. You don't need it squeezing out of the crimp connector.

The reason you'd cur the wire is to verify that TPS is working and to isolate down if the wire is shorted of you have a bad TPS. Eventually, you may have to cut the TPS wire that goes into the EEC. But, you can cut that higher up from the connector. You would likey see a shorted wire.

If you want to aviod any wire cuts, you can do that. But, you MUST FULLY disconnect the battery (both ground and power), and you MUST yanK the EEC from the connector. The, get an 1+amp AC to DC convertor at Wal-mart (~$20). Set it to 5v. Strip the wire ends. Hook the +5v to the red wire VREF, hook the ground to ground. Then, probe the TPS voltage at the EEC pin. You should see .7V+ at idle, and 4.5v+ with the throttle fully open. Of course, make sure that the VREF voltage is near 5V.

hotcobra03 · Dec 6, 2008

Your vref would be pin 46 bg/w to 26 O/W. Koeo is volts 4.0 to 6.0 im expecting no .if no relay next to pcm .pull it tap it than replace it and than ck tps again.

stang&2Birds · Dec 6, 2008

hotcobra03 said:
Yea lets start with codes? What were all the codes? Was 23,53 or 73 present?

90topdown said:
Mine read .15 volts and I had a code 63 (low TPS voltage) so I replaced it with a brand new Ford TPS sensor and the new one reads .15 volts.

.

stang&2Birds · Dec 6, 2008

hotcobra03 said:
Your vref would be pin 46 bg/w to 26 O/W. Koeo is volts 4.0 to 6.0 im expecting no .if no relay next to pcm .pull it tap it than replace it and than ck tps again.

???
Vref is +/- ?2.5%? from the EEC (at the EEC pin) and comes from a single voltage converter inside the EEC. It's a stupid (having a single VREF and single wire) and cheap *ss design. But, it has worked "well enough" for many years.

hotcobra03 · Dec 6, 2008

Im talk at tps connector .this is from fords pin test codes 23,53,63,73. THROTTLE POSITION SENSOR. what that test i gave you is what u asked for .if volts were good than tps is bad if no its a faulty relay or a major short .that you would have more codes and power 4 tps goes thru that relay

hotcobra03 · Dec 6, 2008

Black wire and green. You test should have been 4 continuity pin 46 to 47 .5ohms and less .voltage is ck 46 to 26

stang&2Birds · Dec 6, 2008

hotcobra03 said:
Im talk at tps connector .this is from fords pin test codes 23,53,63,73. THROTTLE POSITION SENSOR. what that test i gave you is what u asked for .if volts were good than tps is bad if no its a faulty relay or a major short .that you would have more codes and power 4 tps goes thru that relay

???

Sorry, from what little I can understand from the garble that you wrote, it is wrong!

It's great that you want to help! But, I suggest that you may want to learn more about the EEC system and electronics.

It seems like you're not even familiar with the basics of how the EEC system is hooked up. See:
Awesome color wiring diagram, by TMoss, for the 88-91 Mustang 5.0 Injectors, Sensors, and Actuators:
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Mustang FAQ - Brake, ABS, Air Bag, Engine Tech Home PageFor Engine, Fuel Injection, and EEC:
Mustang FAQ - Engine Information

Tmoss did a great job on schematics!

Also, check out:
Mustang FAQ - Engine Information A Quick Overview of the Inner Workings of the EEC (Mustang Fuel Injection Computer), by TMoss:
HTML/web version:
EEC IV Inner Workings
PDF version: http://www.veryuseful.com/mustang/tech/engine/EECIVInnerWorkings.pdf

A GREAT, IN DEPTH, Very Technical, Referance for the EEC IV. A MUST READ!:
http://www.veryuseful.com/mustang/tech/engine/eec-IV-Tech98.zip

My guess is that you're a teenager. So, some advice for the future, the way you talk and write, in reality, has a very direct effect on how people view you. When talking about anything technical, text message speak says tons about the person using it.

I think I know "a little" about the TPS and how it's used in the EEC IV systems : Mustang TPS FAQ

Last,, keep up the work on learning about electronics. Of course, *I* think it's worth it.

90topdown · Dec 7, 2008

stang&2Birds said:
So, you need to try a few things to find the problem.
1) Key On Engine Off

2) See if the output voltage (orange wire) changes as you move the throttle to full.
You should see the output go past 4.5v at full throttle.
Again, this is with the Engine Off!

3) If the voltage changes, then you may not have the TPS on correctly, or you have some POS incorrect adjusted and manufactured TB.

4) If the voltage does not change:
Remove the TPS from the TB.
Move the slot by hand.
Notice the output voltage if it changes.
If it changes, you didn't have the TPS on correctly,

If the output voltage does not change, you have much bigger problems - a short somewhere on that wire. It may be on that wire, or it mat be in the EEC.

If you have a short, then you must cut wires to find the short. However, after you cut the wire, you MUST solder the wire and use heat shrink tubing on any wire that is outside the body. If you cut the wire near the EEC (which is best but a pain and you run the risk of cutting the wrong wire), you coukd then just crimp that wire and put heat shrink over it. I suggest using a light coating of dielectric grease on the wire before the crimp. That way, if you get a dash/window leak (thankfully not that common in Stangs), or a wet floors, then that light coating of dielectric grease helps to prevent corrosion. I'm taking about a very light coating. You don't need it squeezing out of the crimp connector.

The reason you'd cur the wire is to verify that TPS is working and to isolate down if the wire is shorted of you have a bad TPS. Eventually, you may have to cut the TPS wire that goes into the EEC. But, you can cut that higher up from the connector. You would likey see a shorted wire.

If you want to aviod any wire cuts, you can do that. But, you MUST FULLY disconnect the battery (both ground and power), and you MUST yanK the EEC from the connector. The, get an 1+amp AC to DC convertor at Wal-mart (~$20). Set it to 5v. Strip the wire ends. Hook the +5v to the red wire VREF, hook the ground to ground. Then, probe the TPS voltage at the EEC pin. You should see .7V+ at idle, and 4.5v+ with the throttle fully open. Of course, make sure that the VREF voltage is near 5V.

Well, it looks like I have a problem here:

1. The TPS in question is a brand new FORD one. Not a cheap POS Vatozone special.

2. With Key On - Engine Off .15 volts between green and black on TPS
4.93 volts at orange wire

With DVM between green and black and moving throttle , voltage goes between .15 to 1.3 volts at WOT.
Moving throttle, voltage is constant 4.93 volts on orange wire. It does not change.

Removed TPS and turned over and moved slot. Voltage remained constant at 4.93 volts on orange wire despite moving slot.

Looks like I have a short somewhere.

How do I chase this down?? Is there any easy way to determine if it is a short or bad EEC??

hotcobra03 · Dec 7, 2008

Im not going to debate till i get copy of those links but in front of me is a 1988 ford service manaual and i also have a 2003 service manaual that breaks down a mustang down to spot welds and rivots.do what you want i will keep following this .

HISSIN50 · Dec 7, 2008

VREF isn't going to change (it might have a tiny variance, which we'll ignore here). I thought I saw mention of orange/tracer being something other than VREF. Not so, AFAIK.

The output (green wire) should range from near 1V to VREF's potential.

If you have another TPS, I'd swap it out.

90topdown · Dec 7, 2008

stang&2Birds said:
If you want to aviod any wire cuts, you can do that. But, you MUST FULLY disconnect the battery (both ground and power), and you MUST yanK the EEC from the connector. The, get an 1+amp AC to DC convertor at Wal-mart (~$20). Set it to 5v. Strip the wire ends. Hook the +5v to the red wire VREF, hook the ground to ground. Then, probe the TPS voltage at the EEC pin. You should see .7V+ at idle, and 4.5v+ with the throttle fully open. Of course, make sure that the VREF voltage is near 5V.

So if I do this ^ and get .7+ at idle and 4.5v+ at WOT------- The problem is in the EEC?????

If I get lower voltage readings, the problem is in the wiring???

hotcobra03 · Dec 7, 2008

Hission ive been waiting for your input.tps was my first problem and i was young and didnt ever get it. Tp test vref is not orange.but is pin 46 to 26 and if failed go to pintest c check reference voltage and 1st test is pin 37 to pin 46 in self test connector.this is for me

stang&2Birds · Dec 8, 2008

90topdown said:
So if I do this ^ and get .7+ at idle and 4.5v+ at WOT------- The problem is in the EEC?????

If I get lower voltage readings, the problem is in the wiring???

So, that is without the EEC plugged in to the big connector? Correct?
If so, then you know the TPS is fine. And, that the wire from the TPS, through all of the connectors, is also good and not shorted to another wire or to ground.

If that's the case, and you measured the voltage at the EEC connector, then, yes, sounds like the EEC is bad. That was the most likely cause. The TPS input goes into a buffer chip before it goes into the microprocessor. That input could have shorted out. Often, that happens from a spike. So, if you plugged or unplugged the TPS in while the ignition was on, that could cause the failure. And, after all, it is just an electronic component, and all electronic components will fail after some amount of time of being on. Many reasons for that.

If you really want to make sure that the EEC is bad, you could do two tests:

Test#1

Disconnect the battery
Cut the TPS input wire into the EEC connector. Cut it far enough away from the connector and firewall so that you can easily fix it.
Plug in the EEC
Turn ignition on
Check the voltage at the cut TPS wire. Check at idle and at WOT.

Test #2:

Get something around a 1K resistor (from ~1000 ohms to ~1500 ohms) at radio shack.
With your DC power supply *OFF*.
Put the resistor inline between your +5V DC power supply and the EEC TPS wire.
Turn on ignition.
Turn on your +5V DC power supply.
Check the voltages on both side of the resistor. The voltages should be the same (~5V and within ~0.2v of each other). My guess is that on the EEC side of the resistor, you'll see a much lower voltage.

I mention the above because I know that you're looking at $100+ for another EEC. Ouch!

You can fix the TPS wire with just a simple crimp connector. Do not just twist and tape the wire. You can get a few of the crimp connectors at Home Depot for ~$1-$2. I use a GB crimping tool. But, vise grips work fine also.

Test#1 and Test#2 will narrow any possible problem down to the EEC.

Good Luck!

joel5.0 · Dec 8, 2008

A very quick way to check it, is to simply install a jumper between VREF and TP signal terminals in the TPS connector, sensor disconnected..... and check the reading at the ECM connector TP signal wire. You should also confirm that a code 53 and or 23 is logged in a KOEO with the jumper installed. LUK

stang&2Birds · Dec 8, 2008

joel5.0 said:
A very quick way to check it, is to simply install a jumper between VREF and TP signal terminals in the TPS connector, sensor disconnected..... and check the reading at the ECM connector TP signal wire. You should also confirm that a code 53 and or 23 is logged in a KOEO with the jumper installed. LUK

Before, my concern about doing that without a resistor inline, is if there is a short on the wire, then it could kill the VREF regulator inside the EEC.

But, I agree, if he already checked the path without the EEC plugged in, and checked the TPS output at the EEC connector, then since the EEC is already very likely bad, there's not much to loose.

Still, using a 1K resistor instead of a jumper is much safer over all.
Digi-Key - 1.0KQBK-ND (Yageo - CFR-25JB-1K0)

Although, you'll pay more for S&H.

Or, search on ebay for
1K Resistor

I saw some listed between ~$3 to $6 including the S&H.

joel5.0 · Dec 9, 2008

The internal regulator in the ECM will take the abuse of a shorted to ground VREF circuit. Same goes with the individual 5 vdc based signals like the ECT and ACT. That electronics design is old, but it can handle some abuse..... .... besides, that is the pinpoint SOP including OBD-II configs.

90topdown · Dec 9, 2008

joel5.0 said:
A very quick way to check it, is to simply install a jumper between VREF and TP signal terminals in the TPS connector, sensor disconnected..... and check the reading at the ECM connector TP signal wire. You should also confirm that a code 53 and or 23 is logged in a KOEO with the jumper installed. LUK

Ok , I pulled the TPS connector and ran a jumper wire between the orange and green posts.

Then I pulled codes and got the following KOEO- 21,23,24 and 67

Using a dedicated ground wire from the DVM back to the neg batt post I got the following at the ECU, KOEO

4.93 volts on the dark green TP signal wire at the ECU - 47
10.67 volts on the red ECU power wire- 57

Looks like a bad ECU??????? Ouch!!

What do you guys think??

stang&2Birds · Dec 10, 2008

90topdown said:
Ok , I pulled the TPS connector and ran a jumper wire between the orange and green posts.

Then I pulled codes and got the following KOEO- 21,23,24 and 67

Using a dedicated ground wire from the DVM back to the neg batt post I got the following at the ECU, KOEO

4.93 volts on the dark green TP signal wire at the ECU - 47
10.67 volts on the red ECU power wire- 57

Looks like a bad ECU??????? Ouch!!

What do you guys think??

Hmm, now I am not "100%" convinced it's the EEC. If it was a fully bad EEC input/buffer, then that test wouldn't have changed the error codes.

It's still possible to have an input buffer that has damage input and overly loads down it's input. From your previous tests, that what it looks like.

Your best test is to put the TPS back in, and cut the TPS wire near the EEC connector. See what that voltage is with the wire cut. Turn OFF The ignition, then see what that voltage is with the wire connected.

Double check that you have the correct wire by also measuring the voltage at the TPS.

If you see the TPS voltage going into the EEC going from ~0.7v with the wire cut to under 0.5v with the wire connected (and VREF was still ~4.8+V), then you have a bad buffer inside the EEC and it's time to get a new one. No choice.

FWIW: If anyone (previous owner, clueless mechanic) ever unplugged or plugged in the TPS connector while the ignition was on, then that damage could occur. Electronic circuits get damaged all the time and then don't fail "for a while". That "while" can be less than a second, or many years. It all depends on the damage that was done to the circuit. Also, there's the much lesser possibility that chip just normally failed that way. However, input buffers "shorting out" in NOT a typical failure by any means (assuming that the input pin always had a good/proper input). And, for that buffer, as long as the TPS stayed connected or not connected while the ignition was on, that buffer input would be fine. Still, that doesn't mean that it "couldn't" happen.

I've argued and explained before WHY it's bad/stupid to plug and unplug sensors with the ignition on. However, since it requires physics, electrical, mechanical, materials, etc knowledge to fully understand why that's the case, people do it, see that the EEC still works, and say "they know better". Hmm, I've been doing chip and board design for over a dozen years. Yea, maybe those people without degrees and direct chip design knowledge really do know better than me. Also, I'm sure they also know better than NASA, the DoD, and physical evidence. Here's some boring stuff:
IEEE - Electrical overstress and electrostatic discharge

Ahh, I found something readable by the public, in easy to understand language, and from a reliable source. Check out figure 7 on page 4:
http://www.3m.com/us/office/meetings/rg/pdfs/g1 basics of static electricity.pdf

For those that really care, here's a quick Google search term:
http://www.google.com/search?q=chip+latent+failures

Replaced TPS Sensor - still get .15 volts ???

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