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Discussion Starter #1
2007 Elise here.

On my way to work yesterday morning (city speed), car suddenly goes to some sort of sputtering idle mode.
Had enough rolling momentum to pull on the side. Then turned the engine off.

Waited a few minutes, started the car, everything seemed fine, except for the CEL on the dashboard.

Quick read on the OBDII scanner shows two codes.
P0638
P2104

I did a bit of research here and on google, but cant really find a real answer to what could potentially be the issue.
P2104 seems to be the code that forces the car to go to idle.
Most likely triggered by P0638, but not sure.
On my way back from work, I tested few things. It seems that as soon as I get close to the 2nd cam, the ECU forces the car into idle mode.


Any idea or direction I should start looking into will be much appreciated before I drive to the dealer :D

Thanks.
Jean
 

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Wow Such Admin
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The first thing I would check is the connector on your throttle body. Make sure it is completely connected into place and that the pins haven't backed out of the connector or anything similar.
 

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2005 Elise
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139 Posts
Quick search found the following:

OBD Code P0638refers to
The Powertrain Control Module (PCM) compares the actual Throttle Possition (TP) with the target TP when the engine is running. If the difference is more than the specification, the PCM determines that there is a throttle actuator control circuit range/performance problem.


Symptoms
Possible sumptoms of OBD code P0638
- Engine Light ON (or Service Engine Soon Warning Light)

Causes
Possible causes of OBD code P0638
- Drive-by-wire control system malfunction - Throttle actuator malfunction - Throttle valve malfunction - PCM malfunction
 

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Discussion Starter #4
Thanks guys,

I will check the throttle body and connectors tomorrow. Hopefully it will be an easy fix and will avoid a trip to the dealership.
 

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Discussion Starter #5 (Edited)
Quick update.

I cleaned the throttle body (well, to be perfectly exact, I watched my mechanic friend cleaning it...).
The throttle body wasn't very dirty, but we wanted to rule that out.
Connectors and pins are all good and clean.

Once cleaned, the check engine light was gone. o_O

No issue for a month and a half, and today on my way to work, it happened again. Bummer.



Something I noticed since the throttle body was cleaned is that the engine sometimes seems to die for a split second, a hiccup.

For example:
Cruising on the highway at a steady 65-70mph, and out of nowhere, engine seems to die for a fraction of a second for no reason, and start again without me doing anything special. Hiccup style. No check engine light.

Driving in city, stop and go. Car sometimes will give me the same "dying for a split second" but in those case I have to give it some throttle to keep it alive. It then throws the check engine and put me in Limp mode...

Not sure what to do at this point. :scratchhead:
 

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Here's my theory -

If the throttle is sticking open ('05s do it often as the throttle gets sloppy and sticks against the side of the bore), then the ECU will try harder and harder to close it. Eventually, it builds up enough force to budge it, and that causes it to slam too far. This really sounds like what you're experiencing given my history with actually working on throttle control code.

I was getting a high idle ('05s can't pull the throttle closed since they're cable), so I cleaned my bore and that helped for awhile, but the problem came back. With the car completely off, see if there is any sideways slop with the throttle.


Sent from AutoGuide.com Free App
 

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Supporting Vendor
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Some 2006 models had an issue with ECU connector pins (female side) stretching out and having poor connection. I would do a ""wiggle test" on your harness and connector at the ECU and see if you can force it to happen. you can also obtain a male pin and do a feel test on all the pins until you find one that doesn't grab well. Repaired a few harness over the years at that connector for similar issues and codes. I have also replaced pedal assemblies for issues and codes similar to this (only once on the pedal).

hope that helps.

T.J.
 
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