TPS readings


bluedemon

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I am getting a code P0123 high voltage. I have done tests on the connector when it wasn't connected to the TPS. The first orange wire I got 5.14 volts, the second orange wire with stripe I was getting 5.08 volts and the third wire was ground. Is that what it means when the code says high voltage? I thought it was supposed to be at 5.0 volts not higher. Any help would be greatly appreciated, Thank you!
 

ItchyDong

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When you unplug the sensor like that with the key on, you get something called bias voltage. Without boring you with the details, that 5 volts USUALLY means nothing, other than the fact that your wiring integrity back to the PCM is good. You need to test the signal wire with the connector plugged in and either backprobe the connector with a Tpin (I recommend) or, you could pierce the wire. Then, you'll get a true signal voltage. With it backprobed and key on, you'll be able to move the throttle by hand, and see the voltage change on the signal wire due to the resistance in the TPS sensor.

Addressing the USUALLY in the above paragraph, there is a chance that the 5 volts that you're signal wire is reporting is because it's shorted to reference voltage. But you can't properly test that with it unplugged. If you plug it back in, backprobe it, and are still getting 5 volts on two of the wires, you've got a short to voltage either by two bare wires touching, a shorted sensor, or a bent pin at the PCM.
 

ItchyDong

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1622751252715.png
 

CharlesHS

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When I have misplaced my back probe tool as ID shows above; I use a paperclip.
The back probe tool that I usually use is insulated with shrink tubing.
You risk damaging your ECU.... if the back probe touches a ground source.
 
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ItchyDong

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When I have misplaced my back probe tool as ID shows above; I use a paperclip.
The back probe tool that I usually use is insulated with shrink tubing.
You risk damaging your ECU.... if the back probe touches a ground source.
Very true. Don't let that T-pin, or paperclip touch ground. Good point.
 
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bluedemon

bluedemon

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When you unplug the sensor like that with the key on, you get something called bias voltage. Without boring you with the details, that 5 volts USUALLY means nothing, other than the fact that your wiring integrity back to the PCM is good. You need to test the signal wire with the connector plugged in and either backprobe the connector with a Tpin (I recommend) or, you could pierce the wire. Then, you'll get a true signal voltage. With it backprobed and key on, you'll be able to move the throttle by hand, and see the voltage change on the signal wire due to the resistance in the TPS sensor.

Addressing the USUALLY in the above paragraph, there is a chance that the 5 volts that you're signal wire is reporting is because it's shorted to reference voltage. But you can't properly test that with it unplugged. If you plug it back in, backprobe it, and are still getting 5 volts on two of the wires, you've got a short to voltage either by two bare wires touching, a shorted sensor, or a bent pin at the PCM.
I did do what you said and when I plugged it in and took the readings I still was getting 5.09 volts on the first (orange) wire. However when I checked the second (orange with stripe) I was getting .78 volts. It did go up as I pushed on the throttle and I didn't notice any sharp spikes or anything but when I got to wide open throttle it was only reading 3.88 volts. Everywhere I've been reading is saying I should be at 4.58 or so at WOT.

Here is what is going on with my Jeep:
I have noticed that when it is running at an Idle it will suddenly shut off and it almost sounds like it is backfiring out of the throttle body. When I do finally get it running were it isn't shutting off you can tell that there is a slight surge in the idle. It has no power and when I do try to accelerate it sounds like it is backfiring while driving. I have all new plugs, fuel injectors. My fuel pressure is at 49psi. I have replaced my TPS and my IACV. I also am in the process of replacing the connector for the IACV because I noticed when I plugged it in the wires were pushing out of the back of the connector and I kept getting a P0505 code. I have it working for now until I get the connector but now the only code I'm getting is P0123. The TPS brand new but it is an Autozone special. I have a Mopar one coming.
Thank you for all your help and advise! I really appreciate it!
 

CharlesHS

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Before throwing away the OEM TPS; get yourself a can of spray contact cleaner (plastic safe) from Walmart.
With the electrical harness disconnected; spray the contact cleaner into the TPS and cycle fully open to fully closed several times.
Blow out with pressurized air or wait 5 minutes before reconnecting the electrical harness.
Retest the voltage readings; you will find your readings will be better.
 
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bluedemon

bluedemon

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I did do what you said and when I plugged it in and took the readings I still was getting 5.09 volts on the first (orange) wire. However when I checked the second (orange with stripe) I was getting .78 volts. It did go up as I pushed on the throttle and I didn't notice any sharp spikes or anything but when I got to wide open throttle it was only reading 3.88 volts. Everywhere I've been reading is saying I should be at 4.58 or so at WOT.

Here is what is going on with my Jeep:
I have noticed that when it is running at an Idle it will suddenly shut off and it almost sounds like it is backfiring out of the throttle body. When I do finally get it running were it isn't shutting off you can tell that there is a slight surge in the idle. It has no power and when I do try to accelerate it sounds like it is backfiring while driving. I have all new plugs, fuel injectors. My fuel pressure is at 49psi. I have replaced my TPS and my IACV. I also am in the process of replacing the connector for the IACV because I noticed when I plugged it in the wires were pushing out of the back of the connector and I kept getting a P0505 code. I have it working for now until I get the connector but now the only code I'm getting is P0123. The TPS brand new but it is an Autozone special. I have a Mopar one coming.
Thank you for all your help and advise! I really appreciate it!
 
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bluedemon

bluedemon

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Okay I replaced the TPS and I replaced the connector for the IACV. I am not getting any codes. When I am under the hood and I rev it the engine itself sounds fine and when it idles it sounds fine, it doesn't die like it would before I replaced the TPS but the funny thing about it is when I am in the car it feels like the the whole jeep is shaking and when I hit the gas it shakes and starts to take off but then it feels like something is holding it back. I don't have a muffler and I only have the Cat. Luckily I live in a county that I don't have to worry about emissions so I took it to my mechanic. If he finds out it's a bad cat then I will just have him drill it out. I will update once it is fixed I hope!

Thanks for all your advise and help so far everyone!
 

CharlesHS

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Okay I replaced the TPS and I replaced the connector for the IACV. I am not getting any codes. When I am under the hood and I rev it the engine itself sounds fine and when it idles it sounds fine, it doesn't die like it would before I replaced the TPS but the funny thing about it is when I am in the car it feels like the the whole jeep is shaking and when I hit the gas it shakes and starts to take off but then it feels like something is holding it back. I don't have a muffler and I only have the Cat. Luckily I live in a county that I don't have to worry about emissions so I took it to my mechanic. If he finds out it's a bad cat then I will just have him drill it out. I will update once it is fixed I hope!

Thanks for all your advise and help so far everyone!
Ask your mechanic to connect a Scan Tool to the OBD2 port and read the voltages from Bank 1 and 2 upstream O2 sensors to see what they are reading. The stumbling you are referring to can be caused by malfunctioning O2 sensors.
The O2 voltage range would be .1 (lean) to .9 (rich); when working properly and warmed up they should modulate .3-.7VDC.
 
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bluedemon

bluedemon

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Thank you for your advise. Wouldn't I get an engine light if it was my O2 sensor? The mechanic looked at the Jeep and I asked him to look at the o2 sensors. He said that everything "electrical" was checking out and felt it had to be more mechanical. He had a much better more advanced tester than I have. He gave it a compression test yesterday and I am supposed to call him later today to find out what the result was. I am not sure what I am going to do if I get bad news. But one thing is for sure, I AM NOT GETTING RID OF MY JEEP! LOL! I have way too much money invested in it already. If it happens to be a valve is that something I can do myself? I have to be honest, I went on you tube to see how hard of a job it is and it seems very overwhelming.

You know now that I think of it, before I registered it in a different county so I wouldn't have to worry about emissions, I tried everything I could to get the "Monitors" to clear but they never did. I never had any engine lights for anything to do with O2 sensors. Do you think if I just replaced both of them that it would help? Right now I'll do anything to not have to tear the engine apart.
 
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CharlesHS

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The O2 sensors do not throw a code unless the heaters are not working... that is why I suggested taking a look at the warmed up operating voltages in Closed Loop.
You can read thru this link and determine if you want to purchase new O2 sensors and the part numbers for your year TJ.

 

ItchyDong

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I'd be curios as to what your LTFT was too. Checking out electrically sounds like he's just seeing a return voltage cycling. I'd want to watch the live data after it's warmed up and at about 2000 rpm to see that they were cycling from rich to lean like they're supposed to.
 
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CharlesHS

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I'd be curios as to what your LTFT was too. Checking out electrically sounds like he's just seeing a return voltage cycling. I'd want to watch the live data after it's warmed up and at about 2000 rpm to see that they were cycling from rich to lean like they're supposed to.
Exactly..... Checking the live data will help narrow down the engines operating problem.
 
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bluedemon

bluedemon

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I honestly don't know much about what you are talking about (learning as I go, SORRY) but he did have the engine reving at 2000 RPM with his scanner connected when I came up there to check how everything was going. He said that at idle you can hear it missing but when you rev it at 2000 RPM it doesn't. He even bought a new coil pack and tried to see if that would make a difference and it didn't. When he was reving it higher than 2000RPM in park it was backfiring pretty good though in the higher RPMS
 
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bluedemon

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Well I just found out that my engine is still good. Compression test read 135 across all cylinders. But now I have NO GAUGES! Everything was working and now none of my gauges work! The Idiot lights come on when you turn the key and start it but none of the gauges work--fuel, RPM, gas, temp, and battery volts. my mechanic is starting to think it is the computer. Also there is a plug here that looks like it goes to an injector that is unplugged by the back of the engine (see picture) does anyone know what it is for?

20210614_120415.jpg
 

ItchyDong

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Glad to hear you found your problem. A little advice: a mechanic who questions a computer without isolating a fault, is not a mechanic you want to mess with. The computer on our TJ is relatively simple, and someone with solid troubleshooting skills can easily isolate faults.

Also, that plug looks like it goes to your intake air temp sensor. Your arm is kind of hiding that intake tube so I can’t tell. But do you have an aftermarket intake? Either way, that plug is probably the source of all of your problems. This engine was designed to run with all sensors. If that is the IAT, I’m surprised you aren’t getting a CEL without a resistor installed in that plug.
 
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bluedemon

bluedemon

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Glad to hear you found your problem. A little advice: a mechanic who questions a computer without isolating a fault, is not a mechanic you want to mess with. The computer on our TJ is relatively simple, and someone with solid troubleshooting skills can easily isolate faults.

Also, that plug looks like it goes to your intake air temp sensor. Your arm is kind of hiding that intake tube so I can’t tell. But do you have an aftermarket intake? Either way, that plug is probably the source of all of your problems. This engine was designed to run with all sensors. If that is the IAT, I’m surprised you aren’t getting a CEL without a resistor installed in that plug.
Thank you for your reply! I already took the Jeep to a different Mechanic that a lot of my friends suggested to me. It is an aftermarket intake but my original one did not have any plugs or a mass air on it. If that would of been on there I would of made sure I got one with the appropriate plug ins/mass air. From what I researched the TJ's don't have MASS sensors. The air intake sensor is on the manifold near the throttle body.

The connector looks exactly like a fuel injector plug but I know it isn't. Being that it has a lock on it I was thinking it had to go to something important.

By the way when I drove the Jeep the different mechanic (maybe a mile away) it died on me 3 times! But no engine codes at all. It would just shut off. It started right up but ran like crap LOL!

Again, thank you for your help and advise!!