P0121, P0123, P2135 - Throttle/Accelerator issues

Hey all,

I've got a 2015 TRD Sport (Bone stock 4.0L V6 w/ ~60K) and while driving down the highway the other night(25 deg F and dry), it died and won't start. While coasting to a stop on the shoulder, I noticed the CEL, A/T Temp and Oil light were all on. I put it in neutral while rolling and tried the ignition. The starter was cranking it over but the engine wouldn't start up. Battery was strong and allowed numerous 5 second ignition attempts before draining down enough that it tripped the anti-theft system(I've noticed it does this when reconnecting power to the system). I pulled the negative battery lead to kill the horn. Charged it back up off a friends vehicle and after a bit more trouble shooting, I decided to call it and pick up where I left off in the morning with my OBD2 scanner.

After $250 to get it out of impound(yes, a few hours on the side of the road was enough on this particular night, while other times I've seen broken down vehicles sit for days), I had it towed to my house to diagnose.

To my surprise, there were no error codes to be found. The live readouts on the scanner were reacting, then remembering that the battery drained and I disconnect the leads, I believe I had inadvertently cleared the codes.

With no direction as to where to look, I start basic testing for spark and fuel. Spark plug test light shows ignition to be working, confirmed with starter fluid in the intake starting it up for 10-20 seconds. First thought is fuel pump, it's not that old, but I notice I can't hear it when I turn the key to the on position(never really noticed it before), but even with my stethoscope on the tank or filler neck, I can't hear the fuel pump priming the lines.

I bang on the tank with a mallet and try again with no success. I checked the scanner again and now I have fault codes P0121, P0123, and P2135 which all relate to the Throttle Positions Sensor voltage and voltage correlation. With the key on, I noticed a whine from the engine bay and tracked it back to the throttle body. Unplug the wiring connector and it goes away. It sounded like the drive was fighting to put it in position it couldn't get to.

A couple of questions:
Is the Throttle Position Sensor integrated into the throttle body assembly? I see where I think it would be, but the whole electronic drive/sensor is riveted to the aluminum TB housing.

Would this kind of error code stop the fuel pump?

Anyone experienced anything like this before?

Thanks in advance, and if anyone asks, I've searched extensively and found very little pertaining to 2nd gen Tacoma throttle position trouble codes.

 

COMPLETE SERVICE MANUAL http://www.customtacos.com/tech.old/files/05FSM/repair.html

 

Fuel pump does not come on until the ecu senses crank rotation.

 

Thanks for the posts with the FSM link and page describing the fuel pump primary circuit.


I’ll dig in and do some more testing after work.

 

I'm probably showing my a$$ here a little, I have very little experience testing for electrical problems, but I'm stuck and afraid I need a new ECM... Adding to my fear that it's the ECM, I replaced the throttle body last night and it still wouldn't start. I'm down to a potential short in the wiring, fingers crossed.

In the wiring connector to the throttle body(T1), with the key on and Accelerator Pedal released, I tested from VTA to ground and VTA2 to ground and both were showing approx 4.16 V. This doesn't appear to be in any normal range on these tables. Granted, I'm not using the intelligent tester mentioned below.

Also, where do I find the E4 ECM connector? I popped out the glovebox and found what looks like the ECM, but it doesn't resemble anything like the image in the diagram below. Image of what I see is below.

 

Did you ever figure out what the problem was? I have the exact same issue and am having trouble figuring out the solution.

Thank you

 

Fuel Pump. About $1000 at the dealership. That was for the entire drop in assembly. If I hadn't been in a time crunch leaving town, I would've just swapped the pump itself and not the entire assembly.

 

Do you know why it gave codes for the throttle position sensor when it was the fuel pump?

 

Hello all and thanks for all the advice period I have a 2019 Tacoma SR5 and had these same issues. My solution however was much simpler. While removing everything in the way to replace The spark plugs, I didn't reconnect all the connectors and the tubes correctly. After 20 minutes of panic and multiple additional videos, I went back and reset every connector that I thought I had taken out in somewhere in the mix took care of it.
I'm much luckier than many of you and did not have to spend any money at the dealer, but the panic was there none the less. Thanks for all the help over the past 4 years

 

This morning my 2008 wouldn't start, exact same symptoms including the whine from the throttle body. I took it apart and realized the whine was the servo trying to keep it closed or close it more when it was in a fully closed position, when the whine was active I couldn't move the butterfly valve by hand, if I turned the ignition off, I could. Trying to decide what system would be trying to close the throttle body, I decided something to do with the throttle position sensor. I came across this video on resetting the TPMS, tried it out and the truck fired right up. Now I had an error code but didn't have a standalone OBD2 reader so I rescued my virtual machine running TechStream and read the codes, P0121, P0123, P2135. Cleared them all but am now wondering if I should be replacing something or how long this fix will last.

 

do you have one of those aftermarket pedal controllers installed? if so i would rip that out and never put one in

the really bad thing about those units is they sandwich into you accelerator pedal connection and then they bias the two hall sensors that return their pedal position voltage back to the ecu. the ecu output 5v to each one and each factory hall sensor in your gas pedal then returns a charted value between about 1.2 v to 5v back to the ecu... note: each one is is linear and there is an offset voltage designed between the two outputs that have to stay linear sloped to each other to avoid the ecu from using an erroneous signal (from a failed hall sensor or emi/rfi noise or whatever. basically fail safe to ignore both inputs and keep your pedal from giving input to the throttle body unless everything is in working order and cross checked by the ecu. the offset is designed by factory Toyota so the ecu can cross check the two and see they are moving linear but a slight offset on voltage of about for conversation sake lets say 1 volt between the two returns (hope that made sense)

now with all that being said here is where those pedal controllers are a bad thing, the pedal controller boxes that people are buying have a circuit card that needs to be powered and needs to be able to supply a bias voltage(et current) by giving an additional matching bias to each return signal to the ecu to let it think you have pressed the pedal farther than you have. depending on your mode, eco, sport WHATEVER.... your car isnt any faster because this isnt the only thing that decides on the rate your throttle body is opening. like i said, the ECU decides the position, rate and direction of your throttle body movement ( its not changing AFR ..its not changing ignition timing nope. you just think your car is snappier because you has to press the pedal less to get the same output and the ecu isnt being bypassed, it still decides how fast it wants to open your throttle body based on wheel speed sensor accel and tons of other things. 300 bucks for that? ok.. ) anyway.....if the aftermarket card gets out of whack for any reason and the biased outputs dont ramp in parallel for whatever internal failed hiccup or reason, the ecu sees this and then cuts the throttle pedal from working and drives your throttle body to home idle for safety. you can limp the vehicle home at idle but your gas pedal doesnt work

so also think about this if you dont want to play russian roulette with the cost of a new ecu, the 5v signal coming out of the ecu going to each sensor is designed with just enough current for those hall sensors not much more overhead current is available on those wires for that 5v to pover anything else, but the circuit card of these aftermarket devises are stealing that 5v thus increasing the current draw on those outputs from the ecu and can burn out your ecu... or it can also accidentally get the return signals out of proportion and cause codes if the controller begins to become faulty. i dont know about any of you all, but im not willing to risk a expensive ECU going bad from over current because of a aftermarket product drawing from it and it was never designed to handle. or because that aftermarket product failed and caused even more current draw or short the 5v output from the ecu and blows it.

now if they wanted to power their pedal controller devices sold everywhere by instead tapping into the 12v switched power pin at the odbii connecter and then stepping it down in their circuit card and using that to bias the hall switch outputs returning to the ecu.. then great. id know my ecu wasnt struggling to provide current to after market stuff and id make damn sure that the sandwich harness wasnt tapping into the ecu to pedal 5v signals before the hall sensors. id make sure it was only tapping the return lines. until them.... no way would i use one of those aftermarket pedal controller units.... an ecu is too expensive to replace. also if the circuit card were powered from the odb source via a step down divider and that circuit card failed, any short of the signal would be after the hall sensor where its returning to ecu and that wont hurt a ecu. but shorting the output of the 5 volt from the ecu going to the hall sensor that would blow your ecu

bottom line, dont know if you have one or if it threw those codes and cause that Throttle body to drive hard to close like that. but if you do have one, it probably hiccuped and caused your issue not hard failed, but an indication of intermittent failures that is a sign its gonna fail hard soon.

note that toyota shields those return wires so no outside noise can affect them if your shield is bad, noise near those wires could have caused them to go outside of proportional schedule.

im assuming your gas pedal wasnt working or you didnt try to start the vehicle again to see if your gas pedal was working before clearing the codes

their is one company in Europe tht is doing this right and using the 12 power from the odbii connector port, but i have issues with other parts of their specific design, but at least they were receptive and said they are working on a possible updgrade to their design. ( i will leave out vendor names because i am not promoting nor affiliated with any of them, but i damn well want to know how their or other vendor products are designed especially for me because i evaluate how they could fail and then that effect on my vehicle. and how could it cause a unsafe or costly situation for me sure things work great when they work great .. but what if the unit i get then fails)

 

It's normal for the PCM to hold the throttle body closed key on engine off, electronic throttle bodies have a spring loaded failsafe that will hold the throttle blade at around 15-20% if power is lost to the throttle body to prevent the engine from stalling.

The humming noise it makes key on engine off is normal and is due to the throttle body motor being duty cycle controlled.