Check engine light on with transmission woes. - Honda-Tech - Honda Forum Discussion

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Check engine light on with transmission woes.

Old 10-19-2018, 06:32 PM
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Default Check engine light on with transmission woes.

Hello.

2003 Civic Coupe with 150,000 Miles and an automatic transmission.

The check engine light came on, and that coincided with shifting problems. The shift problems are as follows:

1) When decelerating from city speed, the down shift is clunky.
2) When shifting from park to reverse or drive, the shift is clunky as well.

There are no up shift problems.

My local shop said the code was referring to the throttle, so the throttle was cleaned up, the check engine light went out, and the shift problems were gone. I then took it for three short test drives. The first 2 test drives showed no issue, but on the third test drive, the light came back on and the shifting problem returned.

If anyone has some suggestions as to my next step, it would be greatly appreciated.

Thanks!
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Old 10-20-2018, 07:34 AM
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Default Re: Check engine light on with transmission woes.

Please go to an auto parts store or visit your mechanic again and request the check engine codes, post them here as P#### (ex. P0301 is a cylinder 1 misfire) That will help us understand what is wrong with the car, or at least what the computer *thinks* is wrong with the car.
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Old 10-20-2018, 08:05 AM
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Default Re: Check engine light on with transmission woes.

Thank you for the reply.

I'll go back to the shop on Monday.

I can't recall if the tech said throttle, or throttle sensor. I also can't conclusively say that cleaning the throttle assembly had any affect, as the whole problem is intermittent.

In the mean time, if there was a problem with the throttle sensor, wouldn't I have engine issues? (the engine runs fine). Also, could a defective throttle sensor, cause the shifting problems I described?
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Old 10-20-2018, 08:36 AM
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Default Re: Check engine light on with transmission woes.

Possibly, as the shifting is only done at certain times under certain throttle positions. e.g. WOT shift would be at 6000 rpm, 20% throttle shift @ 2000 rpm, unless more load, then downshift... etc. The engine and transmission are very close to each other and the ECU has to operate both in near perfect harmony for good operation.
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Old 10-20-2018, 08:58 AM
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Default Re: Check engine light on with transmission woes.

That sounds right to me. Especially given that the code shows a problem with the throttle sensor, and I only have the shifting problem when the check engine light comes on.

Given all that, I think we can accurately conclude that the sensor should be replaced. Do you agree? If so, I'll look into what it entails to replace it myself.

Side Note:

When receiving help on a forum, I like to make a donation to show my thanks. Is there any way to do this on this forum?
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Old 10-20-2018, 09:13 AM
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Default Re: Check engine light on with transmission woes.

Not necessarily the sensor, it could be a clog or some variety of interference on the sensor. I'd wait for that code to determine which sensor might be affected.

There isn't really a way to directly compensate anyone through H-T, and it's not really expected or required, but if you're dead set on it you can PM me
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Old 10-20-2018, 10:09 AM
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Default Re: Check engine light on with transmission woes.

By requesting I go back to my mechanic and get the code again, are you suggesting that the initial diagnostic may be incorrect?
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Old 10-20-2018, 11:49 AM
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Default Re: Check engine light on with transmission woes.

No, not necessarily, but the cleaning could not have been enough. There are 3 intake related sensors, and it would also provide clarity to us (me) to know which sensor they cleaned: Throttle position sensor (TPS), Intake air temperature sensor (IAS), or Mass airflow sensor (MAF). The code would tell us what's what. My guess is it's the MAF sensor, and a new one would probably not be a bad idea given it's seen 150k miles. But just being able to pin down what the issue is in more detail is better for forum diagnosing.
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Old 10-20-2018, 01:20 PM
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Default Re: Check engine light on with transmission woes.

Ok.
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Old 10-22-2018, 10:33 AM
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Default Re: Check engine light on with transmission woes.

If you said you did not have any CEL and codes, I would have suggested that you could have broken engine or transmission mounts.
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