p2138 engine code

[crazylegs]

Just got my yaris 2 months ago, at first when the check engine light would come on my throttle response would just be shitty nothing more, after a few weeks i had a situation that freaked me out. While driving the throttle response went from normal to nothing and my car would just crawl forward at idle whether or not i was flooring the gas peddle. At first this only happened the one time and turning off the car and turning it back on fixed the issue, however in the last week it seems to be happening on a daily basis at random times, and it's driving me crazy!

engine code p2138
symptoms engine comes on and off at random, when engine light is on i have sluggish throttle response, and from time to time i have no throttle response which may go away in a few seconds or can last for as long as 15mins

solutions attempted
1.changed the peddle assembly with the APP sensor cleared the codes and within 5mins of driving the engine light came back on.
2. cleaned the mass air flow sensor, and the throttle body, cleared the codes and was able to drive for an hour without an issue. which made me feel that the issue was that the sensor or throttle body just needed to be cleaned.
3, took off the peddle assembly so i could return it and get my money back, cleared the codes and drove for 12mins then the engine light came back on.

now i'm just confused to hell what should be my next step in trouble shooting this issue. i have a new mass airflow sensor but i don't want to waste the $270 i paid for it putting it on the car just to find out it's not the issue. and if it's the throttle body sensor i feel like i just might as well look for a corolla TB and slap it on and call it a day.

anyone deal with this issue, love to get your feedback on how you tackled it.

[CTScott]

It is definitely not the MAF nor the TB. P2138 indicates a short between VPA and VPA2.

VPA and VPA2 are direct connections between the ECM and accelerator pedal, so the problem is either the pedal (unlikely two bad ones), ECM itself, or the wiring between the two.

[crazylegs]

so my next step should be to physically trace the wires from the peddle to the ECU or is there an easier way of doing that?

thank you again for your input

[Shroomster]

You can check for continuity.....

Sent from my metallic purple honami

[CTScott]

so my next step should be to physically trace the wires from the peddle to the ECU or is there an easier way of doing that?

thank you again for your input

Yes. You would disconnect the pedal connector and the smaller ECM connector

VPA: Red wire on pedal connector
VPA2: Blue wire on pedal connector

On the ECM connector A21 they go to pins 55 and 56 (same colors as other end)

With both ends disconnected, first measure the resistance between the two wires, which should show as an open circuit. Then stick a small piece of wire into the ECM connector to bridge the two wires at that end and measure again. This time the resistance should be very close to zero.

53924

[ezhacker1]

Do you happen to have an external aftermarket throttle controller?
I did and had the same symptoms, and kept on getting p2127 error code, maybe also the code you have too. According to Toyota manual, firm and show pedal depression will allow the car to drive slowly, but that's near impossible to do on a manual car trying to keep her from stalling. I posted a few times about this issue and came to the conclusion that the wiring harness for the controller must be loose and causing the short or bad ground.

[crazylegs]

Thanks for all the info my dumb ass is going to plug away at this tomorrow. The last 2 days however the cars engine light hasnt even come on at all. Should I wait till the light comes on again?

Ezhacker1 I just picked up the car and it looks pretty bone stock.

[CTScott]

Thanks for all the info my dumb ass is going to plug away at this tomorrow. The last 2 days however the cars engine light hasnt even come on at all. Should I wait till the light comes on again?

Ezhacker1 I just picked up the car and it looks pretty bone stock.

With the repercussions of what happens when the error occurs, I would try to troubleshoot it before it happens again. I would look for damaged wire, since it is now intermittent.

[ezhacker1]

Absolutely get it fixed asap. At least with my error codes and pedal issues when it happens, all i had to do was unplug the throttle controller and all fixed.

[crazylegs]

Well im now looking for the ecm I took out the glove box on the passenger side and looked around under the dash and see nothing. Damn

[crazylegs]

Found it in the engine bay on the fireway passenger side

[crazylegs]

Ok still confused

At the pedal connector I have blue, green, black, yellow, brown, white

Brown is the only one the has full continuity regardless if it goes to pin 55 or 56 in the ecm.
Black gets half continuity

Blue has some continuity but it is low continuity in both pins
Yellow is very low continuity on both pins

Green nothing
White nothing

Now what does that info mean? As it looks like the colors dont match up from peddle to ecm for those pins. Should I unplug both ecm connectors to get an better reading?

[crazylegs]

Not sure how to test resistance with the tools I have

[CTScott]

If you have a multimeter, you put it in resistance (Ohms) mode. If you hold the probes apart and look at the screen you will see what an open circuit looks like (most meters will show "OL"). If you then touch the probes together you will see a short circuit (0 or very close to it).

On the pedal connector you are just interested in the red and blue wires. The colors that you mention do not include blue. Can you snap a picture of the connector? You should be seeing red, green, black, blue, brown, white. The fact that your colors are different than the service manual makes me wonder if you car does have a throttle controller installed. Follow the wires up from the pedal connector and see if there is a box with two inline connectors.

[crazylegs]

I never had to use one of those things before

ok this is what I got so far with the multi meter

when I checked the resistance (turn the dial to the horse shoe looking symbol at 200k) these are the numbers I get.

VPA APP a20-6 (Blue) to ECM a21-55 (blue) = 130
VPA2 APP a20-3 (Yellow) to ECM a21-56 (red) = 130

I tested the rest of the connections from the APP to the ECM and I got the value of 0 for each connection

so with that info I got I really still not sure If it means my wiring is good or bad. as I never done this before.

Also I noticed 2 wires the VCP2 a20-1 (white) and the EPA a20-5 (green) both go into the a different connector just above the pedal. and I do have cruise control is this the throttle control system exhacker1 was talking about. I'll have to go see where the blue and yellow wire go to.

also did a little test to the ECM and got these results which I assume means the ECM is working fine but I don't have a clue.

I checked the voltage by connecting the following pins on the APP connector while the ignition was set to ON.

VCPA (a20-4) and EPA (a20-5) = 5.05v
VCP2(a20-1) and EPA2 (a20-2) = 5.05v

[crazylegs]

ok I traced the yellow wire to a drive by wire cruise control module and both the VPA wires to this thing. I wonder if this could be the issue assuming that the other info I posted is good. if I unplug the unit the car runs but I have no peddle control just like when I everything goes bad. so I'm starting to think this thing is the issue.

[CTScott]

I never had to use one of those things before

ok this is what I got so far with the multi meter

when I checked the resistance (turn the dial to the horse shoe looking symbol at 200k) these are the numbers I get.

VPA APP a20-6 (Blue) to ECM a21-55 (blue) = 130
VPA2 APP a20-3 (Yellow) to ECM a21-56 (red) = 130

I tested the rest of the connections from the APP to the ECM and I got the value of 0 for each connection

so with that info I got I really still not sure If it means my wiring is good or bad. as I never done this before.

Also I noticed 2 wires the VCP2 a20-1 (white) and the EPA a20-5 (green) both go into the a different connector just above the pedal. and I do have cruise control is this the throttle control system exhacker1 was talking about. I'll have to go see where the blue and yellow wire go to.

also did a little test to the ECM and got these results which I assume means the ECM is working fine but I don't have a clue.

I checked the voltage by connecting the following pins on the APP connector while the ignition was set to ON.

VCPA (a20-4) and EPA (a20-5) = 5.05v
VCP2(a20-1) and EPA2 (a20-2) = 5.05v


If you have a Rostra cruise control, that would explain the inline connector. If that is the case, that would likely be the culprit.

[crazylegs]

yeah it is a rostra cruise control module is that an after market job or do most Yaris's with cruise control have this model?

[CTScott]

yeah it is a rostra cruise control module is that an after market job or do most Yaris's with cruise control have this model?

It is aftermarket, but Toyota approved aftermarket. Prior to 2009, it was the only dealer installed option for cruise control on a Yaris (even though all Yaris from 2006 on had the functionality built into the ECM). The Rostra cruise control was actually recalled in Canada because of susceptibility to radio transmissions.

[crazylegs]

I just noticed that the rostra wiring was plugged into the original APP a20 connecter so I unplugged it from the rostra wiring and plugged it into the peddle everything seems to work great now. lol damn that was just stupid.

thank you for all your help and suggestions I'm going to drive around now and see how it goes. I think I'm just going to remove all the rostra wiring etc. and maybe do your cruise control DIY when I get a chance. i'll look into that later this year.

[CTScott]

I just noticed that the rostra wiring was plugged into the original APP a20 connecter so I unplugged it from the rostra wiring and plugged it into the peddle everything seems to work great now. lol damn that was just stupid.

thank you for all your help and suggestions I'm going to drive around now and see how it goes. I think I'm just going to remove all the rostra wiring etc. and maybe do your cruise control DIY when I get a chance. i'll look into that later this year.

Go visit your local dealer and take advantage of the recall. I think they uninstall the rostra and give you a hand full of money (since they do not consider there to be an alternative). Then, You can shoot me less than 1/4 of what they pay you for the Rostra and I'll shoot you the OEM cruise control kit.

[ezhacker1]

aha, it WAS a throttle controller, just of a different type lol. Glad to hear things worked out.

[crazylegs]

There is a recall? Just call them up and tell them I want them to remove the unit?

[crazylegs]

aha, it WAS a throttle controller, just of a different type lol. Glad to hear things worked out.

Yeah im glad too lol

[CTScott]

There is a recall? Just call them up and tell them I want them to remove the unit?

Correct

[cbk]

There is a recall? Just call them up and tell them I want them to remove the unit?

Can you please tell us if the problem had appeared after a while since you removed the "Rostra cruise control module" ?
Did you permanently removed that module, or change it with a new one after testing?