Stalls on decel. TPS code P0123

You got the 5.0 volts on the feed wire but what about the other two wires? If you unplug the connector resulting in three open circuits, you should find that 5.0 volts on the feed wire, AND 5.0 volts on the signal wire in the middle. There will be about 0.2 volts on the ground wire. That ground wire is common to some other sensors so if the ground wire is open there will be fault codes set for them too.

That 5.0 volts on the signal wire is there thanks to a "pull-up" resistor in the PCM that forces the voltage to go to a value, (5.0 volts in this case), when there's a defect. That 5.0 volts is what triggers the code. Next, reconnect the connector, then back-probe the signal wire and see what you have for voltage. It should be near 0.5 volts at idle and 4.5 volts at wide-open-throttle. If you find 5.0 volts like the scanner shows, measure the ground wire. If the ground wire has 5.0 volts but none of the other sensors have that on their ground wires, there's a break in that wire up to the splice. If the ground wire has 0.2 volts but the signal wire has 5.0 volts, there's a break in that connector terminal in the plug or on the ground terminal.

As you work the throttle, if the voltage on the signal wire sweeps smoothly from 0.5 volts to 4.5 volts approximately, (0.75 to 4.2 volts is typical and acceptable), but the scanner still shows 5.0 volts for the TPS, there has to be a break in that signal wire.

Holler back with what you find for voltages.

My replies are going to be sporadic due to I'm sitting in a library due to a major house fire.

If you're using a digital voltmeter, the leads don't matter. The black goes to the battery negative post or any bare metal bracket or part of the engine, and the red goes to the point you're taking the reading. If you reverse the leads, you'll just get a negative reading but the value will still be correct.

The place to start is by measuring the signal voltage on the TPS. That has to be done with the ignition switch on but the engine doesn't have to be running. The connector must be plugged in too so you'll have to back-probe through the rubber seal the wires go through.

One wire must have 5.0 volts and the ground wire will have 0.2 volts. The last one is the signal wire. It's voltage must vary from about 0.5 volt at idle to about 4.5 volts at wide-open-throttle. The exact numbers aren't important. What you must not see is that voltage suddenly pop to 0.0 or 5.0 volts as you slowly run the the throttle up and down.

Rather than retype all the possibilities, see what you have on those three wires and holler back with those voltages.

Thank you. It was my cats' fault. I had them in the house overnight because it was so cold. I put them out in the morning, fed and watered 'em, and even treated them to some ice cream, and was only out of the house less than five minutes. Came back in to find a fire in front of the fireplace. Either a log rolled out, which I doubt, or a spark jumped out. At any rate, I hope to back living there within a year.

Those voltages are acceptable. If I were to get picky, you should have 0.2 on the ground wire instead of 0.0 volts, but for diagnostic purposes, if there was a break in the ground circuit, you'd have 5.0 volts on it AND on the signal wire.

0.6 volts on the signal wire is perfect. Typically, anything outside 0.5 to 4.5 volts will set a fault code. This one voltage reading tells us the sensor is okay. You can only have this 0.6 volts if the 5.0 volt feed and 0.0 volt ground circuits, and the sensor itself are okay.

That only leaves two things that can set the fault code. There is a break in the signal wire between the sensor and computer, or there's an intermittent connection in the connector terminals. The easiest way to find that is with a scanner to view live sensor data, but you can do that too with a voltmeter by carefully back-probing the wire at the computer's connector. With a break in the signal wire, you'll have your normal 0.6 volts at idle at the sensor, but you'll find 5.0 volts at the computer, and displayed on the scanner.

There's a "pull-up" resistor in the computer for each sensors' signal wire. It is so big electrically that it has no effect on the circuit when that circuit is working properly, but when the signal wire is broken, the voltage seen by the computer could "float" to some random value due to being connected to the rest of the internal circuitry. The computer could try to run on those erroneous values. The pull-up resistor places 5.0 volts on the signal wire, (only when there's a break in that wire to the sensor), to force it to go to an unacceptable condition and set a fault code.

Since you have a scanner, select the screen that shows sensor data and watch the reading for the TPS. If it's 5.0 volts, look for a break in the signal wire. If it's 0.6 volts, wiggle the connector at the TPS and the wiring harness to see if the voltage changes. If it stays solid, there's one more thing that can cause this code. That's an intermittent contact on the sliding contact inside the sensor. That has the same result as a break in the signal wire and will allow the pull-up resistor to put 5.0 volts on that wire. You'd identify that by slowly running the throttle between idle and wide-open-throttle, by hand. Be aware that all scanner displays respond painfully slowly when looking for this type of intermittent problem, so work the throttle very slowly. Digital voltmeters also respond very slowly. The Engine Computer can detect the slightest momentary blip to 5.0 volts, and set the fault code. Since it's much more sensitive and responsive, if the code sets again while you're working the throttle, replace the sensor, even if you don't see that change on the scanner or voltmeter.

If you do want to replace that sensor, they actually have a pretty low failure rate, so I'd be comfortable with a good used one from a salvage yard.

By "blades", if you're referring to the terminals in the TPS connector, it sounds like you're on the right track. Pull that connector off and on the end you'll see a red, blue, or yellow "pimento" that can be pried out. Once it's removed, that will allow you to release the fingers that hold the terminals in. Remove the terminals, one at a time, and squeeze them just a little so they make better contact. Some types have little strips inside that can be pried up a little from the wire end. Look for corrosion too. Normally if there is any it will be pretty bad, and replacing the terminal is the best cure.

You can also hit the terminals in the sensor with a little strip of sandpaper, and if all else fails, you can bend or twist them just a little so they put more pressure on the mating terminal in the connector.

Dandy. I haven't run into that yet. Happy to hear you solved it.