2005 Tacoma 4.0L Hesitation and No Throttle Response

Truck: 2005 Tacoma DC LB 4.0L with Auto, 70,000 miles, dual Optima Blue Tops using National Luna products, no other major engine/electrical modifications that should relate
Symptoms: Truck has little/no throttle response and hesitation upon acceleration. When symptoms occur the truck feels like it has no power. Biggest symptom though is the little to no throttle response. I can have the throttle at WOT and get no response. Symptoms are sporadic and seem to occur when the truck is cold. Once the truck warms up and/or been cycled on off a couple times the problem goes away but the CEL remains on for a few more cycles.
CEL is on and codes pulled were a P2121 and P2127
Troubleshooting: Took the truck in to the Toyota Dealership and had them run codes and troubleshoot. P2121 is Throttle / Pedal Position Sensor / Switch "D" Circuit Range / Performance. The truck had not had the 90L Pedal Assembly recall completed yet so that was the first step. New pedal assembly and Code 2127 remains. P2127 is Throttle / Pedal Position Sensor / Switch "E" Circuit Low Input. After testing it was found that the voltage was low at throttle position #2. The connectors were removed to check and clean contacts. That did not resolve the issue.

At this point, the dealership recommends replacement of the ECM wiring harness and/or Replacement of the ECM. They say that the only three components to the system are the ECM, Wire Harness, and Throttle Pedal Assembly. I’m still not sold that it’s the ECM or Wiring harness. Both those are pretty big ticket items and I’d hate to replace all that and still have the issue persist. I’m looking for input, ideas, and different approaches from other Toyota owners. Thanks.

 

Has the throttle body been cleaned? How freely does it move?

 

Trying to get more info on this. As of now it has a new pedal assembly which means the pedal position sensors are new. Trying to find info on it> Do you have any leads?

Its been cleaned and seems to be moving fairly freely.

 

I think most likely problem is with wiring harness. Page ES-308 in FSM has testing procedure I would start with that.
Its fall and critters like to hide inside the trucks then they get hungry and chew on things....

 

Solution: IA1; Connector Joining Wire Harness and Wire Harness, Instrument Panel Wire and Engine Room Main Wire (Left Kick Panel)

There is a locking connector at the left kick panel that sits between the PPS/APS and ECM. The connection was not seated properly and locked.

Lesson Learned, when reading schematics pay attention to all the little details and sub notes, don't just assume that one wire goes directly to another location. Simple solution to a problem. Also, don't take the dealers word for problems and actually take the time to troubleshoot potential issues.


Thanks to all those that helped lead to the solution.

 

Wow, I am now having this same problem.

Where is the locking connector located? Any chance someone would have the page/wiring diagram?

Thanks!!

Steve

 

Page 6 to see the schematic. IA1 is the connection that was affecting me. Located on the driver side kick panel.

 

I just started having this problem. When this happens if I leave the accelerator in the same position and not push on the pedal the vehicle slows but the engine does not seem to idle rough like it is not getting fuel. There is just no throttle response. I checked the connectors but no luck. I checked the connector on the accelerator pedal also. No check engine light at all. 2007 Sport TRD 4x4 with 54k on it. Are there any recalls on this problem?

 

Check the connection to the throttle body itself, and maybe clean the MAF sensor... all that area receives blow back of greasy deposits from the intake manifold... I wouldn't go buying a new ECM that would be $$$$$$. Maybe you have some junk built up in the fuel filter or injectors, I'd start cleaning stuff until it fixes, then start taking stuff* apart to make sure everything that is suppose to move, does so without too much effort. (Fuel delivery related stuff) Does it still eventually get WOT or drive normally? You said its mostly when its cold... maybe O2 sensor in the exhaust is dirty or bad and its telling the engine to send/not send fuel...

Just some more .02 cents

 

YEAH, WTH is with that??? My GF and I were out of town for a couple days and when I came back and started poking around under the hood for some spring cleaning I found half of the cotton stuffing under the engine cover was gone and all the rubber vacuum hoses were chowed up under there... I live in a busy apt complex, but was ready to start sniping squirrels from our third floor with a .22. BASTARDS!

 

Had a similar problem....i took out the throttle body and cleaned it with MAF cleaner and wiped it down then i lubed the plate in the throttle body and its running fine and also I have a better feel in my brake pedal cause of better vacuum. Does your brake pedal feel like you have to push it in a little more to stop?

 

It funny you say that. My brake feel softer then they did before. Actually I notice that my brake light stayed on after I released the pedal. It was like the pedal actuator switch was still being contacted by the pedal.

 

Its the loss of vacuum in the engine...clean your throttle body and see how much tighter it feels....the throttle body has alot to do with engine performance...