Stalls on decel. TPS code P0123

Tiny
JARED7976
  • MEMBER
  • 2001 DODGE DURANGO
  • 100,458 MILES
I bought an 01 Durango that needed a timing chain and tensioner (typical). Replaced chain, tensioner, and guides. No bent valves, etc. Engine now runs smooth, with no noise EXCEPT it stalls when throttle is released and the CEL is on. Code P0123 (TPS high voltage) is present. Scan tool shows constant 5 volts (approx). I performed the diagnostic procedure from AllData. It has 5 volt ref on ref volt wire, all wires have almost no resistance between PCM plug and TPS plug, and no short to power or ground when unplugged. The diagnostic flow chart led me to a faulty PCM.
My question is: WHY did the PCM fail. Is there a common problem with the PCM's on these? Is there an underlying cause to the PCM failure? If I replace the PCM, is the new (or reman) one going to fail right away? I am an ASE Certified Master Tech with 20 yrs experience, but never seen this problem before. I rarely EVER condemn PCM's, so it makes me nervous just to put one in without knowing if this is common or hearing from a Chrysler expert.
Do you
have the same problem?
Yes
No
Saturday, June 1st, 2013 AT 2:12 PM

10 Replies

Tiny
CARADIODOC
  • EXPERT
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.
Was this
answer
helpful?
Yes
No
Saturday, June 1st, 2013 AT 8:04 PM
Tiny
WAGS1026
  • MEMBER
Caradiodoc,
I'm experiencing the same p0123 problems, but seeing that I'm not very good with electrical testing I could use some guidance. I dealing with my 2003 grand Cherokee, I have OBD11 scanner and DVM, in regards to your answer above on the Durango could go through the test on TPS advising when you test with key on or key off, and what leads (red/black) go to which terminal on Tps or Pcm or wherever. Sorry for the elementary questions but I could use some help.
Was this
answer
helpful?
Yes
No
Friday, March 21st, 2014 AT 6:20 AM
Tiny
CARADIODOC
  • EXPERT
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.
Was this
answer
helpful?
Yes
No
Friday, March 21st, 2014 AT 4:39 PM
Tiny
WAGS1026
  • MEMBER
Thanks for getting back to me, sorry to hear of your house fire. Hope everyone is ok.

Re Jeep.
With connector on the TPS with key on /engine off.
Back probe of wires reading are as follows.

The orange 5V supply = 5.1 V
the orange/Red signal wire = 0.6 v
the black and light blue GRD = 0.0
Was this
answer
helpful?
Yes
No
Friday, March 21st, 2014 AT 4:49 PM
Tiny
CARADIODOC
  • EXPERT
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.
Was this
answer
helpful?
Yes
No
Saturday, March 22nd, 2014 AT 11:21 AM
Tiny
WAGS1026
  • MEMBER
Thanks for the detailed explanation.
I put everything back together, cleared code and drove vehicle, 5.1 miles code came back. I had my Actron OBD11 scanner hooked up while driving and when code kicked on the ABSOL TPS percentage (not voltage my scanner won't read voltage) the % went crazy jumping all over the place. Drove home 2.3 miles. Pulled PCM connector apart and took the TPS connector off of the TPS sensor. I checked continuity of all 3 TPS wires between PCM and TPS connector and all 3 showed good no breaks in wire. I put both connectors back on and then with the key on/engine off and OBD11 scanner connected I backed probed the TPS wires one by one holding the TPS connector as stationary as I could. When I did this I got no change in the ABSOL TPS %. Then I did my best at holding on to the wires at the TPS connector back probed the TPS wires again and wiggled just the connector trying not to let the wires move. When I did this the ABSOL TPS % on my scanner went crazy again, jumping all over the pace.
My logic (which electrically is flawed most of the time) tells me that one or more of the blades on the TPS are making intermittent contact.
It this a good assumption?
Thanks for your help.
Was this
answer
helpful?
Yes
No
Sunday, March 23rd, 2014 AT 5:27 AM
Tiny
CARADIODOC
  • EXPERT
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.
Was this
answer
helpful?
Yes
No
Sunday, March 23rd, 2014 AT 11:54 AM
Tiny
WAGS1026
  • MEMBER
Hey, Took aftermarket TPS back to AA and they refunded the price. Went to local Jeep dealer (who must have felt sorry for me gave 30% discount) and bought new Mopar TPS. Put in new TPS, clear the code, drive the vehicle for 20 miles so far. No codes, trans shifts correctly, cruise control works, runs smooth, no hesitation. Fingers crossed, but looks like it was a crap aftermarket TPS right out of the box.

Live and learn as they say, buy electrical parts from Chrysler ONLY.

Thank you for all your assistance, it is truly appreciated.
Was this
answer
helpful?
Yes
No
Monday, March 24th, 2014 AT 2:18 PM
Tiny
JARED7976
  • MEMBER
I found the problem with mine was coolant from the axillary coolant pump was leaking down the wiring harness, into the vehicle and caused corrosion in the lowest two terminals in the bulkhead connector under the dash, just above the driver's feet. Cleaned terminals and it corrected the problem. I guess it's actually pretty common.
Was this
answer
helpful?
Yes
No
Monday, May 5th, 2014 AT 4:44 PM
Tiny
CARADIODOC
  • EXPERT
Dandy. I haven't run into that yet. Happy to hear you solved it.
Was this
answer
helpful?
Yes
No
Monday, May 5th, 2014 AT 8:10 PM

Please login or register to post a reply.

Recommended Guides