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steady 2k idle no no throttle action

jaykappyjaykappy Member Posts: 5
edited August 2016 in Mazda
I have a mazda 3 5 door with a 2.5l
The car all of a sudden pegged a 2k idle with no action when I step in the gas. I can drive the car but only to a speed of the 2k idle...there is no response when I step on the gas.

p0123 throttle positioning sensor/switch
p0223 throttle pedal positioner switch

I had the car in a shop and they replaced the whole foot pedal assembly
I brought the car home and replaced the complete throttle body with throttle positioning sensor
Both OEM parts.

i started the car and it was at 2k.
I then shut off the car disconnected the battery waited a few minutes.
I started it and it was a perfect idle with full action on the gas pedal. I thought it was fixed.
I placed it in drive and it went right back to a 2k idle with no pedal and the codes appeared again.
guy next store tried to clear the codes but they came back on in a few seconds.
we reran the codes and the same 2 appeared...

BUT i just replaced them....what the heck is going on....dont know where to go or what to check....PLEASE HELP!!!!


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    thecardoc3thecardoc3 Member Posts: 5,768
    edited August 2016
    The codes mean that the throttle position sensor signals at the PCM are greater than 4.85 volts. When ever I see two sensors both setting high voltage codes the first thing to check is the ground circuit for them. Here is a partial schematic.

    The White/Blu pin D of the throttle body is the ground circuit for the sensors. Measure the voltage "KOEO" (Key on Engine off) to battery negative. It should be .1v or less. You can measure the sensor signals the same way, TP#1 should be approx. .8v (does not have to be exact) and TP#2 should be approx. 4.3v. TP#1 voltage goes up and TP#2 goes down as the throttle opens. By the code description you will see both higher than 4.85v. If you see 5v, which is the reference voltage then the ground circuit is open. If you see higher than 5v, first verify what the reference voltage to the sensor is (white wire). It should be 5v. If that is the case then there is power being applied to the sensor circuits from another source. I'll only address that "IF" that applies here.

    I expect that you are going to measure 5v at the sensor signal pins as well as the ground pin. If that is correct , your next step will be to measure the voltage at pin 2AN (which turns into a yellow wire at the PCM). If you have 0v there then the white/blu wire is broken. If you have 5v there, then the PCM has lost its ground circuit for those sensors.
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    jaykappyjaykappy Member Posts: 5
    OK something else going on....I can start and get a decent idle AT traction control light is off....engine light is still on....
    BUT if I push down on the wires coming from the ECM it sputters and then sends it to the 2k idle and the traction light comes back on....
    It also does this when I put it in reverse...

    if I push down on the wires at the top arrow...which pushes down on the collection of wires at the lower arrow if sends it to the the 2k idle etc...

    Is there something I can check where these wires from the ECM go?????

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    jaykappyjaykappy Member Posts: 5
    I can vend and push on all the wires right at the ECM and nothing happens...only when I push down on the wires going down....
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    jaykappyjaykappy Member Posts: 5
    edited August 2016
    OK I am trying to test the ground etc that you mentioned above.....
    Looking for some clarification:

    1. The plug that goes into the Throttle positioning sensor on the throttle body has a blue/white wire. I pushed a little wire into the female side of the pin.....I hooked a volt meter to this and then to the negative battery terminal correct? WITH the key on but engine not started....I get 22.5 mV or .0225 v ....i think that conversion is correct....
    2. On the two brown wires....think going to the sensor signals as you said....I get 4.3V on one and .35 mV on the other??? .35 mV not .8 volts?????
    3. unclear how to test 2AN....this is one of the wires at the ECM correct...there are two banks of wires that plug into the ECM....think there are a couple yellow wires...not sure where to test or how to find the correct wire...

    Please help...thanks and cheers
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    thecardoc3thecardoc3 Member Posts: 5,768
    Now that you have made some measurements and are comfortable with doing that, start the engine and repeat the measurements while you are manipulating the harness and getting the failure to occur. The flaw is measurable with the above routine and by being able to measure it you get to pinpoint the exact failure and then address it. As far as not knowing which wire is which at the PCM, that's what service information is for. I used a piece of information for instructional purposes which is permitted, but it would be improper to simply republish all of the material. (copy-write laws) You can get full access to schematics and information at a number of sources such as AlldataDIY.com. or Mitchell at http://www.eautorepair.net/Marketing/Default.asp

    As far as the exact throttle position sensor values, the system allows for some tolerance and learns the relationship of the values. They will be different at idle than they are key on engine off, especially if the engine hasn't been running for a couple minutes while you were getting ready to test. The PCM holds the throttle in the start position when the key is first turned on, but if the engine isn't started it will turn the throttle body off and allow the throttle to go completely closed.

    In the shop we also have a scan tool hooked up in order to monitor the data as seen by the computer while we make the live voltage measurements as described. The voltage measurements are done with a four channel digital oscilloscope which first allows us to prove the affected circuit or wire and then at multiple points of that circuit or wire to locate the exact point of the failure
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    jaykappyjaykappy Member Posts: 5
    If I unplug the clip that plugs into the throttle body to test the blue/white wire when running it will stall the engine...confused. Think its time to take this thing in
    how much does this type of diagnosis cost? What should I expect if I take it in?

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    thecardoc3thecardoc3 Member Posts: 5,768
    You don't need to unplug the connector to test that wire. Back probe the connection using a "T" pin. https://www.google.com/?gws_rd=ssl#q=t+pins&tbm=shop Measure the voltage at the throttle body connector, and at the pin 2AN key on engine off and key on engine running with you manipulating the harness and making the problem occur.
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